Irina Ivanova Vaseva

RESEARCH INTERESTS

Plant hormones, ethylene, cytokinins, cell type specificity of hormonal signaling and crosstalk, dehydrins, expression of stress-inducible proteins.

Scopus Publications

Effects of Melatonin Pre- and Post-Drought Treatment on Oxidative Stress Markers and Expression of Proline-Related Transcripts in Young Wheat Plants
Zornitsa Katerova, Dessislava Todorova, Irina I. Vaseva, Elena Shopova, Margarita Petrakova, Martin Iliev, and Iskren Sergiev
MDPI AG
Wheat can tolerate a mild water deficit, but prolonged drought causes a number of detrimental physiological changes resulting in a substantial decrease in productivity. The present study evaluates the potential of the natural plant growth regulator melatonin to alleviate the negative effects of moderate drought in two Bulgarian winter wheat cultivars at the early vegetative stage. Melatonin doses of 75 µM were root-supplemented 24 h before or after the stress period. The levels of several biometric parameters, osmolyte content and stress indicators as well as the expression of genes coding for key enzymes of the proline biosynthesis pathway were analyzed in leaves at the end of the drought stress and after two and four days of recovery. Applied alone, melatonin did not exert significant effects on most of the monitored parameters. Water deprivation negatively affected seedlings’ fresh weight and water content and increased the stress markers and osmolyte levels. These were accompanied by a high accumulation of TaP5CS and TaP5CR transcripts coding for the enzymes Δ-pyrroline-5-carboxylate synthase and Δ-pyrroline-5-carboxylate reductase, respectively. The effect of melatonin in reducing drought stress was similar whether applied before or after exposure, though slightly more effective when used as a pre-treatment.


Drought Protective Effects of Exogenous ABA and Kinetin on Lettuce: Sugar Content, Antioxidant Enzyme Activity, and Productivity
Martynas Urbutis, Irina I. Vaseva, Lyudmila Simova-Stoilova, Dessislava Todorova, Audrius Pukalskas, and Giedrė Samuolienė
MDPI AG
Drought is an environmental stressor that significantly impacts plant growth and development. Comprehending the complexity of drought stress and water utilization in the context of plant growth and development holds significant importance for sustainable agriculture. The aim of this study was to evaluate the effect of exogenously applied phytohormones on lettuce (Lactuca sativa L.) sugar content profiles and antioxidant enzyme activity and productivity. Lettuce plants were grown under normal and drought conditions in a growth chamber with a photoperiod of 14/10 h (day/night). Kinetin and abscisic acid were applied separately and in combinations when the second leaf was fully expanded. The results showed that sugar accumulation and productivity of the pretreated plants under drought were significantly higher than the controls. The perspective offered by this work showed that growth-related and stress-related phytohormones significantly influenced plant sugar metabolism, metabolic profiles, and productivity, thus enabling the control of yield and quality.


Combined Pretreatment with Bioequivalent Doses of Plant Growth Regulators Alleviates Dehydration Stress in Lactuca sativa
Irina I. Vaseva, Iskren Sergiev, Dessislava Todorova, Martynas Urbutis, Giedrė Samuolienė, and Lyudmila Simova-Stoilova
MDPI AG
Plant hormones regulate adaptive responses to various biotic and abiotic stress factors. Applied exogenously, they trigger the natural plant defense mechanisms, a feature that could be implemented in strategies for supporting crop resilience. The potential of the exogenous cytokinin-like acting compound (kinetin), the auxin analogue 1-naphtyl acetic acid (NAA), abscisic acid (ABA) and the ethyleneprecursor 1-aminocyclopropane-1-carboxylic acid (ACC) to mitigate dehydration was tested on Lactuca sativa (lettuce) grown on 12% polyethylene glycol (PEG). Priming with different blends containing these plant growth regulators (PGRs) applied in bioequivalent concentrations was evaluated through biometric measurements and biochemical analyses. The combined treatment with the four compounds exhibited the best dehydration protective effect. The antioxidative enzyme profiling of the PGR-primed individuals revealed increased superoxide dismutase (SOD), catalase and peroxidase activity in the leaves. Immunodetection of higher levels of the rate-limiting enzyme for proline biosynthesis (delta-pyroline-5-carboxylate synthase) in the primed plants coincided with a significantly higher content of the amino acid measured in the leaves. These plants also accumulated particular dehydrin types, which may have contributed to the observed stress-relieving effect. The four-component mix applied by spraying or through the roots exerted similar stress-mitigating properties on soil-grown lettuce subjected to moderate drought.


Ectopic Expression of Distinct PLC Genes Identifies 'Compactness' as a Possible Architectural Shoot Strategy to Cope with Drought Stress
Max van Hooren, Ringo van Wijk, Irina I Vaseva, Dominique Van Der Straeten, Michel Haring, and Teun Munnik
Oxford University Press (OUP)
Abstract Phospholipase C (PLC) has been implicated in several stress responses, including drought. Overexpression (OE) of PLC has been shown to improve drought tolerance in various plant species. Arabidopsis contains nine PLC genes, which are subdivided into four clades. Earlier, OE of PLC3, PLC5 or PLC7 was found to increase Arabidopsis’ drought tolerance. Here, we confirm this for three other PLCs: PLC2, the only constitutively expressed AtPLC; PLC4, reported to have reduced salt tolerance and PLC9, of which the encoded enzyme was presumed to be catalytically inactive. To compare each PLC and to discover any other potential phenotype, two independent OE lines of six AtPLC genes, representing all four clades, were simultaneously monitored with the GROWSCREEN-FLUORO phenotyping platform, under both control- and mild-drought conditions. To investigate which tissues were most relevant to achieving drought survival, we additionally expressed AtPLC5 using 13 different cell- or tissue-specific promoters. While no significant differences in plant size, biomass or photosynthesis were found between PLC lines and wild-type (WT) plants, all PLC-OE lines, as well as those tissue-specific lines that promoted drought survival, exhibited a stronger decrease in ‘convex hull perimeter’ (= increase in ‘compactness’) under water deprivation compared to WT. Increased compactness has not been associated with drought or decreased water loss before although a hyponastic decrease in compactness in response to increased temperatures has been associated with water loss. We propose that the increased compactness could lead to decreased water loss and potentially provide a new breeding trait to select for drought tolerance.


Divergent Cross-Adaptation of Herbicide-Treated Wheat and Triticale Affected by Drought or Waterlogging
Irina I. Vaseva, Margarita Petrakova, Ana Blagoeva, and Dessislava Todorova
MDPI AG
Widely used agrochemicals that do not exert negative effects on crops and selectively target weeds could influence plant resilience under unfavorable conditions. The cross-adaptation of wheat (Triticum aestivum L.) and triticale (×Triticosecale Wittm.) exposed to two environmental abiotic stressors (drought and waterlogging) was evaluated after treatment with a selective herbicide (Serrate®, Syngenta). The ambivalent effects of the herbicide on the two studied crops were particularly distinct in waterlogged plants, showing a significant reduction in wheat growth and better performance of triticale individuals exposed to the same combined treatment. Histochemical staining for the detection of reactive oxygen species (ROS) confirmed that the herbicide treatment increased the accumulation of superoxide anion in the flooded wheat plants, and this effect persisted in the younger leaves of the recovered individuals. Comparative transcript profiling of ROS scavenging enzymes (superoxide dismutase, peroxidase, glutathione reductase, and catalase) in stressed and recovered plants revealed crop-specific variations resulting from the unfavorable water regimes in combination with the herbicide treatment. Short-term dehydration was relatively well tolerated by the hybrid crop triticale and this aligned with the considerable upregulation of genes for L-Proline biosynthesis. Its drought resilience was diminished by herbicide application, as evidenced by increased ROS accumulation after prolonged water deprivation.


Dynamics of Polyamines, Proline, and Ethylene Metabolism under Increasing Cold in Winter Oilseed Rape
Elžbieta Jankovska-Bortkevič, Sigita Jurkonienė, Virgilija Gavelienė, Vaidevutis Šveikauskas, Rima Mockevičiūtė, Irina Vaseva, Dessislava Todorova, Marija Žižytė-Eidetienė, Donatas Šneideris, and Petras Prakas
MDPI AG
Cold stress is among the most important environmental factors reducing the yield of crops. The present study aimed to investigate the impact of increasing cold stress conditions on winter oilseed rape polyamines, proline, and ethylene metabolism in acclimated and non-acclimated winter oilseed rape. This study was carried out under controlled conditions in the laboratory. The winter oilseed rape hybrid ‘Visby’ was used in the experiment. Acclimated and non-acclimated plants were subjected to a two-day-long increasing cold (from −1 °C to −3 °C) treatment. HPTLC, RT-qPCR, spectral analysis, and gas chromatography methods were used to analyse the levels of polyamines, gene expression, proline, and ethylene, respectively. This study showed a decrease in putrescine, spermidine, and spermine content during cold acclimation and a decrease in putrescine and spermidine levels at sub-zero temperatures. There were intensive changes in ADC2 gene expression, proline, and ethylene levels in non-acclimated plants: a substantial increase after exposure to −1 °C temperature and a sharp decrease after exposure to −3 °C temperature. The changes in these parameters were lower or absent in acclimated plants. The phenomena observed in this study add new insights to the knowledge about the plant stress response and suggest questions to be answered in the future.


Heat-Stress-Mitigating Effects of a Protein-Hydrolysate-Based Biostimulant Are Linked to Changes in Protease, DHN, and HSP Gene Expression in Maize
Irina I. Vaseva, Lyudmila Simova-Stoilova, Anelia Kostadinova, Bistra Yuperlieva-Mateeva, Tania Karakicheva, and Valya Vassileva
MDPI AG
The growth-promoting and heat-mitigating effects of a commercially available protein-hydrolysate-based biostimulant, Kaishi, during the early vegetative stage was investigated by applying it as a foliar spray on soil-grown maize plants or in the nutrient solution of hydroponically grown plants. At 10−3 dilution, the biostimulant inhibited germination and delayed the growth progress, while at 10−6–10−12 dilutions, it promoted shoot and root growth. Heat stress caused biomass reduction, decreased leaf pigment content and the chlorophyll a/chlorophyll b (chl a/b) ratio, caused starch depletion, and increased lipid peroxidation. Kaishi priming resulted in the substantial mitigation of negative stress effects, maintaining growth, stabilizing pigment content and the chl a/b ratio, restoring the leaf starch content, lowering the malondialdehyde (MDA) level, and significantly increasing the free proline content. The expression profiles of a set of genes coding for heat shock proteins (HSPs), dehydrins (DHNs), and proteases were analysed using qRT-PCR after heat stress exposure. The biostimulant-treated plants had higher transcript levels of certain HSPs, DHNs, and protease-coding genes, which remained stable or increased after the applied stress. The results demonstrate that very low concentrations of the biostimulant exerted stress-mitigating effects that could be linked to organ-specific changes in the gene expression of certain stress-inducible proteins.


Ethylene signaling in salt-stressed Arabidopsis thaliana ein2-1 and ctr1-1 mutants – A dissection of molecular mechanisms involved in acclimation
Irina I. Vaseva, Lyudmila Simova-Stoilova, Elisaveta Kirova, Kiril Mishev, Thomas Depaepe, Dominique Van Der Straeten, and Valya Vassileva
Elsevier BV
To pinpoint ethylene-mediated molecular mechanisms involved in the adaptive response to salt stress we conducted a comparative study of Arabidopsis thaliana wild type (Col-0), ethylene insensitive (ein2-1), and constitutive signaling (ctr1-1) mutant plants. Reduced germination and survival rates were observed in ein2-1 plants at increasing NaCl concentrations. By contrast, ctr1-1 mutation conferred salt stress tolerance during early vegetative development, corroborating earlier studies. Аll genotypes experienced strong stress as evidenced by the accumulation of reactive oxygen species (ROS) and increased membrane lipid peroxidation. However, the isoenzyme profiles of ROS scavenging enzymes demonstrated a higher peroxidase (POX) activity in ctr1-1 individuals under control and salt stress conditions. A markedly elevated free L-Proline (L-Pro) content was detected in the ethylene constitutive mutant. This coincided with the increased levels of Delta-1-Pyrroline-5-Carboxylate Synthase (P5CS) which is the rate-limiting enzyme from the proline biosynthetic pathway. A stabilized upregulation of a stress-induced P5CS1 splice variant was observed in the ctr1-1 background, which was not documented in the ethylene insensitive mutant ein2-1. Transcript profiling of the major SALT OVERLY SENSITIVE (SOS) pathway players (SOS1, SOS2, and SOS3) revealed altered gene expression in the organs of the ethylene signaling mutants. Overall suppressed SOS expression was observed in the ein2-1 mutants while only the SOS transcript profiles in the ctr1-1 roots were similar to the wild type. Altogether, we provide experimental evidence for ethylene-mediated molecular mechanisms implicated in the acclimation response to salt stress in Arabidopsis, which operate mainly through the regulation of free proline accumulation and enhanced ROS scavenging.


The diverse salt-stress response of arabidopsis ctr1-1 and ein2-1ethylene signaling mutants is linked to altered root auxin homeostasis
Irina I. Vaseva, Kiril Mishev, Thomas Depaepe, Valya Vassileva, and Dominique Van Der Van Der Straeten
MDPI AG
We explored the interplay between ethylene signals and the auxin pool in roots exposed to high salinity using Arabidopsisthaliana wild-type plants (Col-0), and the ethylene-signaling mutants ctr1-1 (constitutive) and ein2-1 (insensitive). The negative effect of salt stress was less pronounced in ctr1-1 individuals, which was concomitant with augmented auxin signaling both in the ctr1-1 controls and after 100 mM NaCl treatment. The R2D2 auxin sensorallowed mapping this active auxin increase to the root epidermal cells in the late Cell Division (CDZ) and Transition Zone (TZ). In contrast, the ethylene-insensitive ein2-1 plants appeared depleted in active auxins. The involvement of ethylene/auxin crosstalk in the salt stress response was evaluated by introducing auxin reporters for local biosynthesis (pTAR2::GUS) and polar transport (pLAX3::GUS, pAUX1::AUX1-YFP, pPIN1::PIN1-GFP, pPIN2::PIN2-GFP, pPIN3::GUS) in the mutants. The constantly operating ethylene-signaling pathway in ctr1-1 was linked to increased auxin biosynthesis. This was accompanied by a steady expression of the auxin transporters evaluated by qRT-PCR and crosses with the auxin transport reporters. The results imply that the ability of ctr1-1 mutant to tolerate high salinity could be related to the altered ethylene/auxin regulatory loop manifested by a stabilized local auxin biosynthesis and transport.


Overexpression of the NMig1 Gene Encoding a NudC Domain Protein Enhances Root Growth and Abiotic Stress Tolerance in Arabidopsis thaliana
Valentin Velinov, Irina Vaseva, Grigor Zehirov, Miroslava Zhiponova, Mariana Georgieva, Nick Vangheluwe, Tom Beeckman, and Valya Vassileva
Frontiers Media SA
The family of NudC proteins has representatives in all eukaryotes and plays essential evolutionarily conserved roles in many aspects of organismal development and stress response, including nuclear migration, cell division, folding and stabilization of other proteins. This study investigates an undescribed Arabidopsis homolog of the Aspergillus nidulans NudC gene, named NMig1 (for Nuclear Migration 1), which shares high sequence similarity to other plant and mammalian NudC-like genes. Expression of NMig1 was highly upregulated in response to several abiotic stress factors, such as heat shock, drought and high salinity. Constitutive overexpression of NMig1 led to enhanced root growth and lateral root development under optimal and stress conditions. Exposure to abiotic stress resulted in relatively weaker inhibition of root length and branching in NMig1-overexpressing plants, compared to the wild-type Col-0. The expression level of antioxidant enzyme-encoding genes and other stress-associated genes was considerably induced in the transgenic plants. The increased expression of the major antioxidant enzymes and greater antioxidant potential correlated well with the lower levels of reactive oxygen species (ROS) and lower lipid peroxidation. In addition, the overexpression of NMig1 was associated with strong upregulation of genes encoding heat shock proteins and abiotic stress-associated genes. Therefore, our data demonstrate that the NudC homolog NMig1 could be considered as a potentially important target gene for further use, including breeding more resilient crops with improved root architecture under abiotic stress.


Expression profiling of dna methyltransferase genes in wheat genotypes with contrasting drought tolerance




The plant hormone ethylene restricts Arabidopsis growth via the epidermis
Irina Ivanova Vaseva, Enas Qudeimat, Thomas Potuschak, Yunlong Du, Pascal Genschik, Filip Vandenbussche, and Dominique Van Der Straeten
Proceedings of the National Academy of Sciences
The gaseous hormone ethylene plays a key role in plant growth and development, and it is a major regulator of stress responses. It inhibits vegetative growth by restricting cell elongation, mainly through cross-talk with auxins. However, it remains unknown whether ethylene controls growth throughout all plant tissues or whether its signaling is confined to specific cell types. We employed a targeted expression approach to map the tissue site(s) of ethylene growth regulation. The ubiquitin E3 ligase complex containing Skp1, Cullin1, and the F-box protein EBF1 or EBF2 (SCFEBF1/2) target the degradation of EIN3, the master transcription factor in ethylene signaling. We coupled EBF1 and EBF2 to a number of cell type-specific promoters. Using phenotypic assays for ethylene response and mutant complementation, we revealed that the epidermis is the main site of ethylene action controlling plant growth in both roots and shoots. Suppression of ethylene signaling in the epidermis of the constitutive ethylene signaling mutant ctr1-1 was sufficient to rescue the mutant phenotype, pointing to the epidermis as a key cell type required for ethylene-mediated growth inhibition.


Cell type specificity of plant hormonal signals: Case studies and reflections on ethylene
I. I. Vaseva, F. Vandenbussche, D. Simon, K. Vissenberg, and D. Van Der Straeten
Pleiades Publishing Ltd
In the light of increasing evidence that plant growth and development depend on signals perceived in distinct cell types where hormonal inputs are transformed into orchestrated responses triggering a plethora of physiological processes, we reflect on the case of ethylene signaling. Experimental approaches to address cell type-specificity of the ethylene response are discussed and future challenges in ethylene signaling studies are outlined.


Transcript profiling of serine- and cysteine protease inhibitors in Triticum aestivum varieties with different drought tolerance
I.I. Vaseva, G. Zehirov, E. Kirova, and L. Simova-Stoilova
Springer Science and Business Media LLC
A high number of protease inhibitors (PI) have been identified in diverse plant species but information about their role in plant stress responses is still fragmentary. Transcript profiling of six published serine and cysteine protease inhibitor sequences in water-deprived plants from four winter wheat (Triticum aestivum) varieties with varying tolerance was performed in order to outline PIs predominantly accumulating under drought. Expression was analyzed by real time RT-qPCR. Considerable transcript accumulation of Bowman–Birk type PI WALI3 (BBPI) was detected in drought stressed leaves suggesting an important regulatory role of BBPI in adjustment of protein metabolism in leaves under dehydration. Serpin transcripts were less represented in water-deprived plants. Transient accumulation of cystatin transcripts revealed organ-specificity. Under drought cystatin and serpin expression in the leaves of the most drought tolerant variety “Katya” tended to preserve relatively stable levels close to the controls. This preliminary data will serve for future detailed study of regulation of proteolysis in winter wheat subjected to unfavorable environmental factors for development of molecular-based strategies for selection of tolerant varieties.


Changes in 2-DE protein profile of white and red clover leaves in response to waterlogging stress and recovery




Extreme climatic events: Impacts of drought and high temperature on physiological processes in agronomicallyimportant plants
Urs Feller and Irina I. Vaseva
Frontiers Media SA
Climate models predict more frequent and more severe extreme events (e.g. heat waves, extended drought periods, flooding) in many regions for the next decades. The impact of adverse environmental conditions on crop plants is ecologically and economically relevant. This review is focused on drought and heat effects on physiological status and productivity of agronomically important plants. Stomatal opening represents an important regulatory mechanism during drought and heat stress since it influences simultaneously water loss via transpiration and CO2 diffusion into the leaf apoplast which further is utilized in photosynthesis. Along with the reversible short-term control of stomatal opening, stomata and leaf epidermis may produce waxy deposits and irreversibly down-regulate the stomatal conductance and non-stomatal transpiration. As a consequence photosynthesis will be negatively affected. Rubisco activase - a key enzyme in keeping the Calvin cycle functional – is heat-sensitive and may become a limiting factor at elevated temperature. The accumulated reactive oxygen species during stress represent an additional challenge under unfavorable conditions. Drought and heat cause accumulation of free amino acids which are partially converted into compatible solutes such as proline. This is accompanied by lower rates of both nitrate reduction and de novo amino acid biosynthesis. Protective proteins (e.g. dehydrins, chaperones, antioxidant enzymes or the key enzyme for proline biosynthesis) play an important role in leaves and may be present at higher levels under water deprivation or high temperatures. On the whole plant level, effects on long-distance translocation of solutes via xylem and phloem and on leaf senescence (e.g. anticipated, accelerated or delayed senescence) are important. The factors mentioned above are relevant for the overall performance of crops under drought and heat and must be considered for genotype selection and breeding programs.


Identification and expression of different dehydrin subclasses involved in the drought response of Trifolium repens
Irina Ivanova Vaseva, Iwona Anders, and Urs Feller
Elsevier BV
Reverse transcribed RNAs coding for YnKn, YnSKn, SKn, and KS dehydrin types in drought-stressed white clover (Trifolium repens) were identified and characterized. The nucleotide analyses revealed the complex nature of dehydrin-coding sequences, often featured with alternative start and stop codons within the open reading frames, which could be a prerequisite for high variability among the transcripts originating from a single gene. For some dehydrin sequences, the existence of natural antisense transcripts was predicted. The differential distribution of dehydrin homologues in roots and leaves from a single white clover stolon under normal and drought conditions was evaluated by semi-quantitative RT-PCR and immunoblots with antibodies against the conserved K-, Y- and S-segments. The data suggest that different dehydrin classes have distinct roles in the drought stress response and vegetative development, demonstrating some specific characteristic features. Substantial levels of YSK-type proteins with different molecular weights were immunodetected in the non-stressed developing leaves. The acidic SK2 and KS dehydrin transcripts exhibited some developmental gradient in leaves. A strong increase of YK transcripts was documented in the fully expanded leaves and roots of drought-stressed individuals. The immunodetected drought-induced signals imply that Y- and K-segment containing dehydrins could be the major inducible Late Embryogenesis Abundant class 2 proteins (LEA 2) that accumulate predominantly under drought.


Dehydrin expression as a potential diagnostic tool for cold stress in white clover
Irina Ivanova Vaseva, Iwona Anders, Bistra Yuperlieva-Mateeva, Rosa Nenkova, Anelia Kostadinova, and Urs Feller
Elsevier BV
Cold acclimation is important for crop survival in environments undergoing seasonal low temperatures. It involves the induction of defensive mechanisms including the accumulation of different cryoprotective molecules among which are dehydrins (DHN). Recently several sequences coding for dehydrins were identified in white clover (Trifolium repens). This work aimed to select the most responsive to cold stress DHN analogues in search for cold stress diagnostic markers. The assessment of dehydrin transcript accumulation via RT-PCR and immunodetection performed with three antibodies against the conserved K-, Y-, and S-segment allowed to outline different dehydrin types presented in the tested samples. Both analyses confirmed that YnKn dehydrins were underrepresented in the controls but exposure to low temperature specifically induced their accumulation. Strong immunosignals corresponding to 37-40 kDa with antibodies against Y- and K-segment were revealed in cold-stressed leaves. Another 'cold-specific' band at position 52-55 kDa was documented on membranes probed with antibodies against K-segment. Real time RT-qPCR confirmed that low temperatures induced the accumulation of SKn and YnSKn transcripts in leaves and reduced their expression in roots. Results suggest that a YnKn dehydrin transcript with GenBank ID: KC247805 and the immunosignal at 37-40 kDa, obtained with antibodies against Y- and K-segment are reliable markers for cold stress in white clover. The assessment of SKn (GenBank ID: EU846208) and YnSKn (GenBank ID: KC247804) transcript levels in leaves could serve as additional diagnostic tools.


The response of plants to drought stress: The role of dehydrins, chaperones, proteases and protease inhibitors in maintaining cellular protein function




Protein changes and proteolytic degradation in red and white clover plants subjected to waterlogging
Veselin Stoychev, Lyudmila Simova-Stoilova, Irina Vaseva, Anelia Kostadinova, Rosa Nenkova, Urs Feller, and K. Demirevska
Springer Science and Business Media LLC
Red (Trifolium pratense L., cv. “Start”) and white clover varieties (Trifolium repens L., cv. “Debut” and cv. “Haifa”) were waterlogged for 14 days and subsequently recovered for the period of 21 days. Physiological and biochemical responses of the clover varieties were distinctive, which suggested different sensitivity toward flooding. The comparative study of morphological and biochemical parameters such as stem length, leaflet area, dry weight, protein content, protein pattern and proteolytic degradation revealed prominent changes under waterlogging conditions. Protease activity in the stressed plants increased significantly, especially in red clover cv. “Start”, which exhibited eightfold higher azocaseinolytic activity compared to the control. Changes in the protein profiles were detected by SDS-PAGE electrophoresis. The specific response of some proteins (Rubisco, Rubisco-binding protein, Rubisco activase, ClpA and ClpP protease subunits) toward the applied stress was assessed by immunoblotting. The results characterized the red clover cultivar “Start” as the most sensitive toward waterlogging, expressing reduced levels of Rubisco large and small subunits, high content of ClpP protease subunits and increased activity of protease isoforms.


Natural antisense transcripts of Trifolium repens dehydrins
Irina I Vaseva and Urs Feller
Informa UK Limited
The recently described complex nature of some dehydrin-coding sequences in Trifolium repens could explain the considerable variability among transcripts originating from a single gene.1 For some of the sequences the existence of natural antisense transcripts (NATs), which could form sense-antisense (SAS) pairs, was predicted. The present study demonstrates that cis-natural antisense transcripts of 2 dehydrin types (YnKn and YnSKn) accumulate in white clover plants subjected to treatments with polyethylene glycol (PEG), abscisic acid (ABA), and high salt concentration. The isolated YnKn cis-NATs mapped to sequence site enriched in alternative start codons. Some of the sense-antisense pairs exhibited inverse expression with differing profiles which depended on the applied stress. A natural antisense transcript coding for an ABC F family protein (a trans-NAT) which shares short sequence homology with YnSKn dehydrin was identified in plants subjected to salt stress. Forthcoming experiments will evaluate the impact of NATs on transcript abundances, elucidating the role of transcriptional and post-transcriptional interferences in the regulation of dehydrin levels under various abiotic stresses.


Antioxidant response to drought in red and white clover
Irina Vaseva, Yasar Akiscan, Lyudmila Simova-Stoilova, Anelia Kostadinova, Rosa Nenkova, Iwona Anders, Urs Feller, and Klimentina Demirevska
Springer Science and Business Media LLC
Antioxidant response to drought in red (Trifolium pratense L., cv. “Start”) and white clover (Trifolium repens L, cv. “Haifa” and cv. “Debut”) grown as soil cultures was evaluated in water-deprived and recovered plants. Drought provoked oxidative stress in leaves confirmed by the considerable changes in electrolyte leakage, malondialdehyde, hydrogen peroxides and proline contents. Immunoblot of Δ-1-pyrroline-5-carboxylate synthetase (P5CS), which catalyzes the first two steps in proline biosynthesis, revealed strong induction of the enzyme in red clover plants submitted to drought. Water-deprived white clover plants exhibited distinct P5CS profiles. This was related to different drought tolerance of the studied T. repens cultivars. Isoenzyme analyses of superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) demonstrated certain differences in antioxidant defence among the tested varieties. It was confirmed that MnSOD (in both T. repens and T pratense) and FeSOD (in T. repens) isoforms were the most affected by drought. The red clover cultivar “Start” exhibited the lowest FeSOD and POX activities which could contribute to its poor performance under water deprivation.


Drought, high temperature, and their combination affect ultrastructure of chloroplasts and mitochondria in wheat (Triticum aestivum L.) leaves
B. Grigorova, V. Vassileva, D. Klimchuk, I. Vaseva, K. Demirevska, and U. Feller
Informa UK Limited
Plants experience a number of limiting factors, as drought and heat, which are often coinciding stress factors in natural environment. This study evaluated the changes in mesophyll cell ultrastructure in the leaves of two varieties of winter wheat (Triticum aestivum L.), differing in their drought tolerance, under individual or combined drought and heat treatment. Although the individual stress factors affected leaf ultrastructure, the damaging effect of the combined drought and heat was more pronounced and manifested certain differences between genotypes. Chloroplasts and mitochondria were affected in a variety-specific manner under all adverse treatments. The organelles of the drought-tolerant Katya were better preserved than those in the sensitive variety Sadovo. Leaf ultrastructure can be considered as one of the important characteristics in the evaluation of the drought susceptibility of different wheat varieties.


Ethylene in vegetative development: A tale with a riddle
Filip Vandenbussche, Irina Vaseva, Kris Vissenberg, and Dominique Van Der Straeten
Wiley
The vegetative development of plants is strongly dependent on the action of phytohormones. For over a century, the effects of ethylene on plants have been studied, illustrating the profound impact of this gaseous hormone on plant growth, development and stress responses. Ethylene signaling is under tight self-control at various levels. Feedback regulation occurs on both biosynthesis and signaling. For its role in developmental processes, ethylene has a close and reciprocal relation with auxin, another major determinant of plant architecture. Here, we discuss, in view of novel findings mainly in the reference plant Arabidopsis, how ethylene is distributed and perceived throughout the plant at the organ, tissue and cellular levels, and reflect on how plants benefit from the complex interaction of ethylene and auxin, determining their shape. Furthermore, we elaborate on the implications of recent discoveries on the control of ethylene signaling.


A critical look at the microalgae biodiesel
Georgi Petkov, Albena Ivanova, Ivan Iliev, and Irina Vaseva
Wiley
The quantitative production of microalgae oil is often overestimated. The cost of the salts invested in the production of 1 kg algal diesel approximates the actual price of 1 kg mineral diesel. Total sum of electrical energy expenses for production of biodiesel from microalgae is several-fold higher than the energy income from combustion of the same quantity. The biological value of cultivated microalgae as food is much higher than as fuel. An opinion is shared that money ought to be invested in microalgal biomass production as a food additive, forage, and pharmaceuticals. The aim is to prevent making too hasty steps and investments in microalgal biodiesel.

RECENT SCHOLAR PUBLICATIONS

Phenotypic Diversity and Abiotic Stress Tolerance Among Vicia ervilia (L.) Willd. Accessions
S Petrova, T Stoilova, V Velinov, II Vaseva, L Simova-Stoilova
Plants 14 (7), 1008 2025



Effects of Melatonin Pre-and Post-Drought Treatment on Oxidative Stress Markers and Expression of Proline-Related Transcripts in Young Wheat Plants
Z Katerova, D Todorova, II Vaseva, E Shopova, M Petrakova, M Iliev, ...
International Journal of Molecular Sciences 25 (22), 12127 2024



Drought Protective Effects of Exogenous ABA and Kinetin on Lettuce: Sugar Content, Antioxidant Enzyme Activity, and Productivity
M Urbutis, II Vaseva, L Simova-Stoilova, D Todorova, A Pukalskas, ...
Plants 13 (12), 1641 2024



Ectopic Expression ofDistinct PLC Genes Identifies ‘Compactness’ as a Possible Architectural Shoot Strategy to Cope with Drought Stress
M van Hooren, R van Wijk, II Vaseva, D Van Der Straeten, M Haring, ...
Plant and Cell Physiology 65 (6), 885-903 2024



Combined Pretreatment with Bioequivalent Doses of Plant Growth Regulators Alleviates Dehydration Stress in Lactuca sativa
II Vaseva, I Sergiev, D Todorova, M Urbutis, G Samuolienė, ...
Horticulturae 10 (6), 544 2024



Stress in Lactuca sativa
I Vaseva, I Sergiev, D Todorova, M Urbutis, G Samuoliene, ...
2024



OPEN ACCESS EDITED BY
VN Vassileva, II Vaseva, J Li, G Jang, H Kim, J Jang, S Seomun, Y Yoon
Model Organisms in Plant Science: Arabidopsis thaliana, 45 2023



Divergent Cross-Adaptation of Herbicide-Treated Wheat and Triticale Affected by Drought or Waterlogging
II Vaseva, M Petrakova, A Blagoeva, D Todorova
International Journal of Molecular Sciences 24 (15), 12503 2023



Dynamics of polyamines, proline, and ethylene metabolism under increasing cold in winter oilseed rape
E Jankovska-Bortkevič, S Jurkonienė, V Gavelienė, V Šveikauskas, ...
International Journal of Molecular Sciences 24 (14), 11402 2023



Ectopic Expression of Distinct PLC Genes Identifies ‘Compactness’ as Novel Architectural Shoot Strategy to Cope with Drought Stress
M Hooren, R van Wijk, II Vaseva, D Van Der Straeten, M Haring, T Munnik
bioRxiv, 2023.06. 02.543233 2023



Heat-Stress-Mitigating Effects of a Protein-Hydrolysate-Based Biostimulant Are Linked to Changes in Protease, DHN, and HSP Gene Expression in Maize
II Vaseva, L Simova-Stoilova, A Kostadinova, B Yuperlieva-Mateeva, ...
Agronomy 12 (5), 1127 2022



Bowman-Birk protese inhibitor gene expression in Phaseolus vulgaris – organ specificity and induction under abiotic stresses
I Vaseva, K Ivanova, L Simova-Stoilova
Annual of Sofia University “St. Kliment Ohridski” Faculty of Biology 107 (4 2022



Ethylene signaling in salt-stressed Arabidopsis thaliana ein2-1 and ctr1-1 mutants–a dissection of molecular mechanisms involved in acclimation
II Vaseva, L Simova-Stoilova, E Kirova, K Mishev, T Depaepe, ...
Plant Physiology and Biochemistry 167, 999-1010 2021



The Diverse Salt-Stress Response of Arabidopsis ctr1-1 and ein2-1 Ethylene Signaling Mutants Is Linked to Altered Root Auxin Homeostasis
II Vaseva, K Mishev, T Depaepe, V Vassileva, D Van Der Straeten
Plants 10 (3), 452 2021



Overexpression of the NMig1 Gene Encoding a NudC Domain Protein Enhances Root Growth and Abiotic Stress Tolerance in Arabidopsis thaliana
V Velinov, I Vaseva, G Zehirov, M Zhiponova, M Georgieva, ...
Frontiers in Plant Science 11, 815 2020



Expression profiling of DNA methyltransferase genes in wheat genotypes with contrasting drought tolerance.
V Vassileva, I Vaseva, A Dimitrova
Bulgarian Journal of Agricultural Science 25 (5) 2019



The plant hormone ethylene restricts Arabidopsis growth via the epidermis
II Vaseva, E Qudeimat, T Potuschak, Y Du, P Genschik, F Vandenbussche, ...
Proceedings of the National Academy of Sciences 115 (17), E4130-E4139 2018



Cell type specificity of plant hormonal signals: case studies and reflections on ethylene
II Vaseva, F Vandenbussche, D Simon, K Vissenberg, D Van Der Straeten
Russian Journal of Plant Physiology 63, 577-586 2016



Transcript profiling of serine- and cysteine protease inhibitors in Triticum aestivum varieties with different drought tolerance
II Vaseva, G Zehirov, E Kirova, L Simova-Stoilova
Cereal Research Communications 44 (1), 79-88 2016



Aminopeptidase activities in roots and leaves of drought stressed winter wheat seedlings
L Simova-Stoilova, E Kirova, G Zehirov, I Vaseva, U Feller
Genet Plant Physiol 6, 116-34 2016

MOST CITED SCHOLAR PUBLICATIONS

Proteolytic activity and cysteine protease expression in wheat leaves under severe soil drought and recovery
L Simova-Stoilova, I Vaseva, B Grigorova, K Demirevska, U Feller
Plant Physiology and Biochemistry 48 (2-3), 200-206 2010
Citations: 223



Extreme climatic events: impacts of drought and high temperature on physiological processes in agronomically important plants
U Feller, II Vaseva
Frontiers in Environmental Science 2, 39 2014
Citations: 171



Ethylene in vegetative development: a tale with a riddle
F Vandenbussche, I Vaseva, K Vissenberg, D Van Der Straeten
New Phytologist 2012
Citations: 165



The plant hormone ethylene restricts Arabidopsis growth via the epidermis
II Vaseva, E Qudeimat, T Potuschak, Y Du, P Genschik, F Vandenbussche, ...
Proceedings of the National Academy of Sciences 115 (17), E4130-E4139 2018
Citations: 148



Combined drought and heat stress in wheat: changes in some heat shock proteins
B Grigorova, I Vaseva, K Demirevska, U Feller
Biologia plantarum 55, 105-111 2011
Citations: 132



Drought-induced leaf protein alterations in sensitive and tolerant wheat varieties
K Demirevska, L Simova-Stoilova, V Vassileva, I Vaseva, B Grigorova, ...
Gen Appl Plant Physiol 34 (1-2), 79-102 2008
Citations: 108



Drought, high temperature, and their combination affect ultrastructure of chloroplasts and mitochondria in wheat (Triticum aestivum L.) leaves
B Grigorova, V Vassileva, D Klimchuk, I Vaseva, K Demirevska, U Feller
Journal of Plant Interactions 7 (3), 204-213 2012
Citations: 72



A critical look at the microalgae biodiesel
G Petkov, A Ivanova, I Iliev, I Vaseva
European Journal of Lipid Science and Technology 114 (2), 103-111 2012
Citations: 70



The response of plants to drought stress: the role of dehydrins, chaperones, proteases and protease inhibitors in maintaining cellular protein function
I Vaseva, J Sabotič, J Šuštar-Vozlič, V Meglič, M Kidrič, K Demirevska, ...
Droughts: new research 1, 1-45 2012
Citations: 67



Expression of selected heat shock proteins after individually applied and combined drought and heat stress
B Grigorova, II Vaseva, K Demirevska, U Feller
Acta physiologiae plantarum 33, 2041-2049 2011
Citations: 65



Drought stress tolerance of red and white clover–comparative analysis of some chaperonins and dehydrins
I Vaseva, Y Akiscan, K Demirevska, I Anders, U Feller
Scientia horticulturae 130 (3), 653-659 2011
Citations: 57



Abscisic acid and late embryogenesis abundant protein profile changes in winter wheat under progressive drought stress
II Vaseva, BS Grigorova, LP Simova‐Stoilova, KN Demirevska, U Feller
Plant Biology 12 (5), 698-707 2010
Citations: 51



Antioxidant response to drought in red and white clover
I Vaseva, Y Akiscan, L Simova-Stoilova, A Kostadinova, R Nenkova, ...
Acta Physiologiae Plantarum 34, 1689-1699 2012
Citations: 50



Identification and expression of different dehydrin subclasses involved in the drought response of Trifolium repens
II Vaseva, I Anders, U Feller
Journal of plant physiology 171 (3-4), 213-224 2014
Citations: 45



Response of Pisum Sativum Cytokinin Oxidase/Dehydrogenase Expression and Specific Activity to Drought Stress and Herbicide Treatments
I Vaseva-Gemisheva, D Lee, E Karanov
Plant Growth Regulation 46, 199-208 2005
Citations: 37



Photosynthetic responses of nitrate-fed and nitrogen-fixing soybeans to progressive water stress
E Kirova, N Tzvetkova, I Vaseva, G Ignatov
Journal of Plant Nutrition 31 (3), 445-458 2008
Citations: 29



Effect of temperature stress on the endogenous cytokinin content in Arabidopsis thaliana (L.) Heynh plants
D Todorova, T Genkov, I Vaseva-Gemisheva, V Alexieva, E Karanov, ...
Acta Physiologiae Plantarum 27, 13-18 2005
Citations: 28



Protein changes and proteolytic degradation in red and white clover plants subjected to waterlogging
V Stoychev, L Simova-Stoilova, I Vaseva, A Kostadinova, R Nenkova, ...
Acta Physiologiae Plantarum 35, 1925-1932 2013
Citations: 25



Heat-Stress-Mitigating Effects of a Protein-Hydrolysate-Based Biostimulant Are Linked to Changes in Protease, DHN, and HSP Gene Expression in Maize
II Vaseva, L Simova-Stoilova, A Kostadinova, B Yuperlieva-Mateeva, ...
Agronomy 12 (5), 1127 2022
Citations: 23



Droughts: new research
DF Neves, JD Sanz
Nova Science Publishers 2012
Citations: 19