Young-Joon Park
@snu.ac.kr
Scopus Publications
Scholar Citations
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Scopus Publications
Young-Joon Park and P. Seo
The circadian clock may help to control the development patterns which allow the florets on a sunflower head to go through their final stages of maturation at precisely the right time.
Young‐Joon Park, Bo Eun Nam, and Chung‐Mo Park
Wiley
ABSTRACTCoordinated morphogenic adaptation of growing plants is critical for their survival and propagation under fluctuating environments. Plant morphogenic responses to light and warm temperatures, termed photomorphogenesis and thermomorphogenesis, respectively, have been extensively studied in recent decades. During photomorphogenesis, plants actively reshape their growth and developmental patterns to cope with changes in light regimes. Accordingly, photomorphogenesis is closely associated with diverse growth hormonal cues. Notably, accumulating evidence indicates that light‐directed morphogenesis is profoundly affected by two recently identified phytochemicals, karrikins (KARs) and strigolactones (SLs). KARs and SLs are structurally related butenolides acting as signaling molecules during a variety of developmental steps, including seed germination. Their receptors and signaling mediators have been identified, and associated working mechanisms have been explored using gene‐deficient mutants in various plant species. Of particular interest is that the KAR and SL signaling pathways play important roles in environmental responses, among which their linkages with photomorphogenesis are most comprehensively studied during seedling establishment. In this review, we focus on how the phytochemical and light signals converge on the optimization of morphogenic fitness. We also discuss molecular mechanisms underlying the signaling crosstalks with an aim of developing potential ways to improve crop productivity under climate changes.
Jae Young Kim, Young-Joon Park, June-Hee Lee, and Chung-Mo Park
Oxford University Press (OUP)
Abstract Morphogenic adaptation of young seedlings to light environments is a critical developmental process that ensures plant survival and propagation, as they emerge from the soil. Photomorphogenic responses are facilitated by a network of light and growth hormonal signals, such as auxin and gibberellic acid (GA). Karrikins (KARs), a group of butenolide compounds produced from burning plant materials in wildfires, are known to stimulate seed germination in fire-prone plant species. Notably, recent studies support that they also regulate seedling growth, while underlying molecular mechanisms have been unexplored yet. Here, we demonstrate that SUPPRESSOR OF MAX2 1 (SMAX1), a negative regulator of KAR signaling, integrates light and KAR signals into GA–DELLA pathways that regulate hypocotyl growth during seedling establishment. We found that SMAX1 facilitates degradation of DELLA proteins in the hypocotyls. Interestingly, light induces the accumulation of SMAX1 proteins, and SMAX1-mediated degradation of DELLA is elevated in seedling establishment during the dark-to-light transition. Our observations indicate that SMAX1-mediated integration of light and KAR signals into GA pathways elaborately modulates seedling establishment.
Young-Joon Park, Jae Young Kim, and Chung-Mo Park
Oxford University Press (OUP)
Abstract Plant thermosensors help optimize plant development and architecture for ambient temperatures, and morphogenic adaptation to warm temperatures has been extensively studied in recent years. Phytochrome B (phyB)-mediated thermosensing and the gene regulatory networks governing thermomorphogenic responses are well understood at the molecular level. However, it is unknown how plants manage their responsiveness to fluctuating temperatures in inducing thermomorphogenic behaviors. Here, we demonstrate that SUPPRESSOR OF MAX2 1 (SMAX1), known as a karrikin signaling repressor, enhances the thermosensitivity of hypocotyl morphogenesis in Arabidopsis thaliana. Hypocotyl thermomorphogenesis was largely disrupted in SMAX1-deficient mutants. SMAX1 interacts with phyB to alleviate its suppressive effects on the transcription factor activity of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), promoting hypocotyl thermomorphogenesis. Interestingly, the SMAX1 protein is slowly destabilized at warm temperatures, preventing hypocotyl overgrowth. Our findings indicate that the thermodynamic control of SMAX1 abundance serves as a molecular gatekeeper for phyB function in thermosensitizing PIF4-mediated hypocotyl morphogenesis.
June-Hee Lee, Young-Joon Park, Jae Young Kim, and Chung-Mo Park
Oxford University Press (OUP)
Abstract Leaf senescence is an active developmental process that is tightly regulated through extensive transcriptional and metabolic reprogramming events, which underlie controlled degradation and relocation of nutrients from aged or metabolically inactive leaves to young organs. The onset of leaf senescence is coordinately modulated by intrinsic aging programs and environmental conditions, such as prolonged darkness and temperature extremes. Seedlings growing under light deprivation, as often experienced in severe shading or night darkening, exhibit an accelerated senescing process, which is mediated by a complex signaling network that includes sugar starvation responses and light signaling events via the phytochrome B (phyB)-PHYTOCHROME-INTERACTING FACTOR (PIF) signaling routes. Notably, recent studies indicate that nonstressful ambient temperatures profoundly influence the onset and progression of leaf senescence in darkness, presumably mediated by the phyB-PIF4 signaling pathways. However, it is not fully understood how temperature signals regulate leaf senescence at the molecular level. Here, we demonstrated that low ambient temperatures repress the nuclear export of phyB and the nuclear phyB suppresses the transcriptional activation activity of ethylene signaling mediator ETHYLENE INSENSITIVE3 (EIN3), thus delaying leaf senescence. Accordingly, leaf senescence was insensitive to low ambient temperatures in transgenic plants overexpressing a constitutively nuclear phyB form, as observed in ein3 eil1 mutants. In contrast, leaf senescence was significantly promoted in phyB-deficient mutants under identical temperature conditions. Our data indicate that phyB coordinately integrates light and temperature cues into the EIN3-mediated ethylene signaling pathway that regulates leaf senescence under light deprivation, which would enhance plant fitness under fluctuating natural environments.
Young-Joon Park, Jae Young Kim, June-Hee Lee, Shin-Hee Han, and Chung-Mo Park
Elsevier BV
Jae Young Kim, Young-Joon Park, June-Hee Lee, Zee Hwan Kim, and Chung-Mo Park
Oxford University Press (OUP)
Abstract The gaseous phytohormone ethylene plays vital roles in diverse developmental and environmental adaptation processes, such as fruit ripening, seedling establishment, mechanical stress tolerance and submergence escape. It is also known that in the light, ethylene promotes hypocotyl growth by stimulating the expression of PHYTOCHROME INTERACTING FACTOR3 (PIF3) transcription factor, which triggers microtubule reorganization during hypocotyl cell elongation. In particular, ethylene has been implicated in plant responses to warm temperatures in recent years. However, it is currently unclear how ethylene signals are functionally associated with hypocotyl thermomorphogenesis at the molecular level. Here, we show that ETHYLENE-INSENSITIVE3 (EIN3)-mediated ethylene signals attenuate hypocotyl thermomorphogenesis by suppressing auxin response. At warm temperatures, when the activity of the PIF4 thermomorphogenesis promoter is prominently high, the ethylene-activated EIN3 transcription factor directly induces the transcription of ARABIDOPSIS PP2C CLADE D7 (APD7) gene encoding a protein phosphatase that inactivates the plasma membrane (PM) H+-ATPase proton pumps. In conjunction with the promotive role of the PM H+-ATPases in hypocotyl cell elongation, our observations strongly support that the EIN3-directed induction of APD7 gene is linked with the suppression of auxin-induced cell expansion, leading to the reduction in thermomorphogenic hypocotyl growth. Our data demonstrate that APD7 acts as a molecular hub that integrates ethylene and auxin signals into hypocotyl thermomorphogenesis. We propose that the ethylene–auxin signaling crosstalks via the EIN3-APD7 module facilitate the fine-tuning of hypocotyl thermomorphogenesis under natural environments, which often fluctuate in a complex manner.
Shin-Hee Han, Young-Joon Park, and Chung-Mo Park
Springer Science and Business Media LLC
Shin-Hee Han, Young-Joon Park, and Chung-Mo Park
Springer Science and Business Media LLC
Bo Eun Nam, Young-Joon Park, Kyung-Eun Gil, Ju-Heon Kim, Jae Geun Kim, and Chung-Mo Park
Springer Science and Business Media LLC
Abstract Background It is widely perceived that mechanical or thigmomorphogenic stimuli, such as rubbing and bending by passing animals, wind, raindrop, and flooding, broadly influence plant growth and developmental patterning. In particular, wind-driven mechanical stimulation is known to induce the incidence of radial expansion and shorter and stockier statue. Wind stimulation also affects the adaptive propagation of the root system in various plant species. However, it is unknown how plants sense and transmit the wind-derived mechanical signals to launch appropriate responses, leading to the wind-adaptive root growth. Results Here, we found that Brachypodium distachyon, a model grass widely used for studies on bioenergy crops and cereals, efficiently adapts to wind-mediated lodging stress by forming adventitious roots (ARs) from nonroot tissues. Experimental dissection of wind stimuli revealed that not bending of the mesocotyls but physical contact of the leaf nodes with soil particles triggers the transcriptional induction of a group of potential auxin-responsive genes encoding WUSCHEL RELATED HOMEOBOX and LATERAL ORGAN BOUNDARIES DOMAIN transcription factors, which are likely to be involved in the induction of AR formation. Conclusions Our findings would contribute to further understanding molecular mechanisms governing the initiation and development of ARs, which will be applicable to crop agriculture in extreme wind climates.
Young-Joon Park, June-Hee Lee, Jae Young Kim, and Chung-Mo Park
Informa UK Limited
ABSTRACT It is well-known that even small changes in ambient temperatures by a few degrees profoundly affect plant growth and morphology. This architectural property is intimately associated with global warming. In particular, under warm temperature conditions, plants exhibit distinct morphological changes, such as elongation of hypocotyls and leaf petioles, formation of small, thin leaves, and leaf hyponasty that describes an upward bending of leaf petioles. These thermoresponsive morphological adjustments are termed thermomorphogenesis. Under warm temperature conditions, the PHYTOCHROME INTERACTING FACTOR 4 (PIF4) transcription factor is thermoactivated and stimulates the transcription of the YUCCA8 gene encoding an auxin biosynthetic enzyme, promoting hypocotyl elongation. Notably, these thermomorphogenic growth is influenced by daylength or photoperiod, displaying relatively high and low thermomorphogenic hypocotyl growth during the nighttime under short days and long days, respectively. We have recently reported that the photoperiod signaling regulator GIGANTEA (GI) thermostabilizes the REPRESSOR OF ga1-3 transcription factor, which is known to attenuate the PIF4-mediated thermomorphogenesis. We also found that the N-terminal domain of GI interacts with PIF4, possibly destabilizing the PIF4 proteins. We propose that the GI-mediated shaping of photoperiodic rhythms of hypocotyl thermomorphogenesis helps plant adapt to fluctuations in daylength and temperature environments occurring during seasonal transitions.
Young-Joon Park, Jae Young Kim, June-Hee Lee, Byoung-Doo Lee, Nam-Chon Paek, and Chung-Mo Park
Elsevier BV
June-Hee Lee, Jae Young Kim, Jeong-Il Kim, Young-Joon Park, and Chung-Mo Park
Springer Science and Business Media LLC
Young-Joon Park and Chung-Mo Park
Springer Science and Business Media LLC
Jae Young Kim, Young-Joon Park, June-Hee Lee, and Chung-Mo Park
Informa UK Limited
ABSTRACT Directional and non-directional environmental cues are able to induce polar behaviors of plants, which are termed tropic and nastic movements, respectively. While molecular mechanisms underlying the directionality of tropic movements are relatively well studied, it is poorly understood how the polarity of nastic movements is determined in response to non-directional stimuli, such as ambient temperatures. It has recently been shown that thermal induction of leaf hyponasty is stimulated by developmentally programmed polar auxin transport in Arabidopsis. Under warm environments, the PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) transcription factor binds to the promoter of PINOID (PID) gene, whose gene product modulates the polar trafficking of the auxin transporter PIN-FORMED 3 (PIN3). Notably, PIF4 binding to the PID promoter occurs predominantly in the abaxial petiole cells than the adaxial petiole cells, leading to differential PID expression and thus asymmetric auxin accumulation in the petiole cells. In addition, ASYMMETRIC LEAVES 1 (AS1), the well-characterized leaf polarity-determining epigenetic regulator, promotes the PID expression by modulating the patterns of histone 4 acetylation (H4Ac) in the PID chromatin. These observations demonstrate that developmental programming of the thermonastic leaf movement through polar auxin distribution enables plants to bend their leaves upward in response to non-directional thermal stimuli, contributing to cooling plant body temperatures under warm temperature conditions. We propose that a developmentally predetermined polarity plays a major role in governing the directionality of various nastic movements in plants.
Young-Joon Park, Hyo-Jun Lee, Kyung-Eun Gil, Jae Young Kim, June-Hee Lee, Hyodong Lee, Hyung-Taeg Cho, Lam Dai Vu, Ive De Smet, and Chung-Mo Park
Oxford University Press (OUP)
The developmentally programmed polarity of the auxin response underlies thermo-induced leaf hyponasty Plants exhibit diverse polar behaviors in response to directional and nondirectional environmental signals, termed tropic and nastic movements, respectively. The ways in which plants incorporate directional information into tropic behaviors is well understood, but it is less well understood how nondirectional stimuli, such as ambient temperatures, specify the polarity of nastic behaviors. Here, we demonstrate that a developmentally programmed polarity of auxin flow underlies thermo-induced leaf hyponasty in Arabidopsis (Arabidopsis thaliana). In warm environments, PHYTOCHROME-INTERACTING FACTOR4 (PIF4) stimulates auxin production in the leaf. This results in the accumulation of auxin in leaf petioles, where PIF4 directly activates a gene encoding the PINOID (PID) protein kinase. PID is involved in polarization of the auxin transporter PIN-FORMED3 to the outer membranes of petiole cells. Notably, the leaf polarity-determining ASYMMETRIC LEAVES1 (AS1) directs the induction of PID to occur predominantly in the abaxial petiole region. These observations indicate that the integration of PIF4-mediated auxin biosynthesis and polar transport, and the AS1-mediated developmental shaping of polar auxin flow, coordinate leaf thermonasty, which facilitates leaf cooling in warm environments. We believe that leaf thermonasty is a suitable model system for studying the developmental programming of environmental adaptation in plants.
Young-Joon Park, June-Hee Lee, Jae Young Kim, and Chung-Mo Park
Frontiers Media SA
Precise control of the developmental phase transitions, which ranges from seed germination to flowering induction and senescence, is essential for propagation and reproductive success in plants. Flowering induction represents the vegetative-to-reproductive phase transition. An extensive array of genes controlling the flowering transition has been identified, and signaling pathways that incorporate endogenous and environmental cues into the developmental phase transition have been explored in various plant species. Notably, recent accumulating evidence indicate that multiple transcripts are often produced from many of the flowering time genes via alternative RNA splicing, which is known to diversify the transcriptomes and proteasomes in eukaryotes. It is particularly interesting that some alternatively spliced protein isoforms, including COβ and FT2β, function differentially from or even act as competitive inhibitors of the corresponding functional proteins by forming non-functional heterodimers. The alternative splicing events of the flowering time genes are modulated by developmental and environmental signals. It is thus necessary to elucidate molecular schemes controlling alternative splicing and functional characterization of splice protein variants for understanding how genetic diversity and developmental plasticity of the flowering transition are achieved in optimizing the time of flowering under changing climates. In this review, we present current knowledge on the alternative splicing-driven control of flowering time. In addition, we discuss physiological and biochemical importance of the alternative splicing events that occur during the flowering transition as a molecular means of enhancing plant adaptation capabilities.
Shin-Hee Han, Young-Joon Park, and Chung-Mo Park
Informa UK Limited
ABSTRACT It is widely perceived that plant responses to environmental temperatures are profoundly influenced by light conditions. However, it is unknown how light signals modulate plant thermal responses and what photoreceptors are responsible for the light regulation of thermal adaptive process. We have recently reported that phytochrome B (phyB)-mediated red light signals prime the ASCORBATE PEROXIDASE 2 (APX2)-mediated detoxification reaction of reactive oxygen species (ROS), a well-known biochemical process that mediates the acquisition of thermotolerance under high temperature conditions. It is interesting that red light influences the HEAT SHOCK FACTOR A1 (HSFA1)-stimulated activation of the APX2 transcription, which is otherwise responsive primarily to stressful high temperatures. Blue light also efficiently primes the APX2-mediated induction of thermotolerance. In natural habitats, temperatures fluctuate according to the light/dark cycles with temperature peaks occurring during the daytime. It is thus apparent that plants utilize light information to prepare for upcoming high temperature spells.
Shin-Hee Han, Young-Joon Park, and Chung-Mo Park
Oxford University Press (OUP)
Reactive oxygen species (ROS) serve as critical signaling mediators in plant adaptation responses to environmental stimuli. ROS biosynthesis and metabolism should be tightly regulated, because they often impose oxidative damage on biological molecules, such as DNA and proteins, and on cellular structures. It is known that at high temperatures, ROS rapidly accumulate in plant tissues. Thus, a quick activation of ROS-scavenging systems is necessary for thermal adaptation. However, it is largely unknown how the thermo-induced ROS-detoxifying capacity is enhanced by environmental factors at the molecular level. Here, we demonstrated that environmental light primes the thermally induced ROS detoxification process for development of thermotolerance in Arabidopsis. While the ROS detoxification capacity was markedly enhanced in light-pre-treated plants at high temperatures, its enhancement was not as evident in dark-pre-treated plants. ASCORBATE PEROXIDASE 2 (APX2) is a representative ROS-scavenging enzyme that is activated under heat stress conditions. It was observed that the thermal induction of the APX2 gene was more prominent in light-pre-treated plants than in dark-pre-treated plants. Notably, the light-gated APX2 gene induction was compromised in Arabidopsis mutants lacking the red light photoreceptor phytochrome B (phyB). Furthermore, exogenous application of the antioxidant ascorbate recovered the heat-sensitive phenotype of the phyB mutant. These observations indicate that light-primed ROS-detoxifying capability is intimately linked with the induction of thermotolerance. We propose that the phyB-mediated light priming of ROS detoxification is a key component of thermotolerant adaptation in plants.
Young-Joon Park and Chung-Mo Park
Informa UK Limited
ABSTRACT High but nonstressful temperatures profoundly affect plant growth and developmental processes, termed thermomorphogenesis. Thermo-induced hypocotyl elongation is a typical thermomorphogenic trait, which contributes to cooling plant organs. It is known that external light signals and the circadian clock coordinate rhythmic hypocotyl growth. However, it was unclear how light, temperature, and circadian rhythms are harmonized during hypocotyl thermomorphogenesis. We have recently demonstrated that the E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) is activated at warm temperatures. It is notable that warm temperatures induce the nuclear import of COP1, facilitating degradation of ELONGATED HYPOCOTYL 5 (HY5) and this biochemical event is uncoupled from light conditions. Furthermore, the thermo-induced HY5 protein turnover occurs independent of circadian rhythms, indicating that the COP1-HY5 module conveys warm temperature information. Meanwhile, the clock components, including CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), convey timing information for the rhythmic thermomorphogenic growth. These molecular mechanisms enable a coincidence between warm temperature signaling and circadian rhythms, which explains the distinct rhythms of hypocotyl growth at warm temperatures.
Hyo-Jun Lee, Young-Joon Park, Jun-Ho Ha, Ian T. Baldwin, and Chung-Mo Park
Elsevier BV
Young‐Joon Park, Hyo‐Jun Lee, Jun‐Ho Ha, Jae Young Kim, and Chung‐Mo Park
Wiley
Plants adjust their architecture to optimize growth and reproductive success under changing climates. Hypocotyl elongation is a pivotal morphogenic trait that is profoundly influenced by light and temperature conditions. While hypocotyl photomorphogenesis has been well characterized at the molecular level, molecular mechanisms underlying hypocotyl thermomorphogenesis remains elusive. Here, we demonstrate that the E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) conveys warm temperature signals to hypocotyl thermomorphogenesis. To investigate the roles of COP1 and its target ELONGATED HYPOCOTYL 5 (HY5) during hypocotyl thermomorphogenesis, we employed Arabidopsis mutants that are defective in their genes. Transgenic plants overexpressing the genes were also produced. We examined hypocotyl growth and thermoresponsive turnover rate of HY5 protein at warm temperatures under both light and dark conditions. Elevated temperatures trigger the nuclear import of COP1, thereby alleviating the suppression of hypocotyl growth by HY5. While the thermal induction of hypocotyl growth is circadian-gated, the degradation of HY5 by COP1 is uncoupled from light responses and timing information. We propose that thermal activation of COP1 enables coincidence between warm temperature signaling and circadian rhythms, which allows plants to gate hypocotyl thermomorphogenesis at the most profitable time at warm temperatures.
Kyung-Eun Gil, Mi-Jeong Park, Hyo-Jun Lee, Young-Joon Park, Shin-Hee Han, Young-Ju Kwon, Pil Joon Seo, Jae-Hoon Jung, and Chung-Mo Park
Wiley
The circadian clock control of CONSTANS (CO) transcription and the light-mediated stabilization of its encoded protein coordinately adjust photoperiodic flowering by triggering rhythmic expression of the floral integrator flowering locus T (FT). Diurnal accumulation of CO is modulated sequentially by distinct E3 ubiquitin ligases, allowing peak CO to occur in the late afternoon under long days. Here we show that CO abundance is not simply targeted by E3 enzymes but is also actively self-adjusted through dynamic interactions between two CO isoforms. Alternative splicing of CO produces two protein variants, the full-size COα and the truncated COβ lacking DNA-binding affinity. Notably, COβ, which is resistant to E3 enzymes, induces the interaction of COα with CO-destabilizing E3 enzymes but inhibits the association of COα with CO-stabilizing E3 ligase. These observations demonstrate that CO plays an active role in sustaining its diurnal accumulation dynamics during Arabidopsis photoperiodic flowering.
Hyo-Jun Lee, Young-Joon Park, Pil Joon Seo, Ju-Heon Kim, Hee-Jung Sim, Sang-Gyu Kim, and Chung-Mo Park
Oxford University Press (OUP)
Phosphorylation of NPR by the protein kinase SnRK2.8 allows nuclear import of NPR1, an essential step in systemic acquired resistance. In plants, necrotic lesions occur at the site of pathogen infection through the hypersensitive response, which is followed by induction of systemic acquired resistance (SAR) in distal tissues. Salicylic acid (SA) induces SAR by activating NONEXPRESSER OF PATHOGENESIS-RELATED GENES1 (NPR1) through an oligomer-to-monomer reaction. However, SA biosynthesis is elevated only slightly in distal tissues during SAR, implying that SA-mediated induction of SAR requires additional factors. Here, we demonstrated that SA-independent systemic signals induce a gene encoding SNF1-RELATED PROTEIN KINASE 2.8 (SnRK2.8), which phosphorylates NPR1 during SAR. The SnRK2.8-mediated phosphorylation of NPR1 is necessary for its nuclear import. Notably, although SnRK2.8 transcription and SnRK2.8 activation are independent of SA signaling, the SnRK2.8-mediated induction of SAR requires SA. Together with the SA-mediated monomerization of NPR1, these observations indicate that SA signals and SnRK2.8-mediated phosphorylation coordinately function to activate NPR1 via a dual-step process in developing systemic immunity in Arabidopsis thaliana.