Phytohormones, including jasmonates (JAs), gibberellin, ethylene, abscisic acid, and auxin, integrate endogenous developmental cues with environmental signals to regulate plant growth, development, ...and defense. JAs are well-recognized lipid-derived stress hormones that regulate plant adaptations to biotic stresses, including herbivore attack and pathogen infection, as well as abiotic stresses, including wounding, ozone, and ultraviolet radiation. An increasing number of studies have shown that JAs also have functions in a remarkable number of plant developmental events, including primary root growth, reproductive development, and leaf senescence. Since the 1980s, details of the JA biosynthesis pathway, signaling pathway, and crosstalk during plant growth and development have been elucidated. Here, we summarize recent advances and give an updated overview of JA action and crosstalk in plant growth and development.
Stamens are the plant male reproductive organs essential for plant fertility. Proper development of stamens is modulated by environmental cues and endogenous hormone signals. Deficiencies in ...biosynthesis or perception of the phytohormone jasmonate (JA) attenuate stamen development, disrupt male fertility, and abolish seed production in Arabidopsis thaliana. This study revealed that JA-mediated stamen development and seed production are regulated by a bHLH-MYB complex. The IIIe basic helix-loop-helix (bHLH) transcription factor MYC5 acts as a target of JAZ repressors to function redundantly with other IIIe bHLH factors such as MYC2, MYC3, and MYC4 in the regulation of stamen development and seed production. The myc2 myc3 myc4 myc5 quadruple mutant exhibits obvious defects in stamen development and significant reduction in seed production. Moreover, these IIIe bHLH factors interact with the MYB transcription factors MYB21 and MYB24 to form a bHLH-MYB transcription complex and cooperatively regulate stamen development. We speculate that the JAZ proteins repress the bHLH-MYB complex to suppress stamen development and seed production, while JA induces JAZ degradation and releases the bHLH-MYB complex to subsequently activate the expression of downstream genes essential for stamen development and seed production.
Integration of diverse environmental and endogenous signals to coordinately regulate growth, development, and defense is essential for plants to survive in their natural habitat. The hormonal signals ...gibberellin (GA) and jasmonate (JA) antagonistically and synergistically regulate diverse aspects of plant growth, development, and defense. GA and JA synergistically induce initiation of trichomes, which assist seed dispersal and act as barriers to protect plants against insect attack, pathogen infection, excessive water loss, and UV irradiation. However, the molecular mechanism underlying such synergism between GA and JA signaling remains unclear. In this study, we revealed a mechanism for GA and JA signaling synergy and identified a signaling complex of the GA pathway in regulation of trichome initiation. Molecular, biochemical, and genetic evidence showed that the WD-repeat/bHLH/MYB complex acts as a direct target of DELLAs in the GA pathway and that both DELLAs and JAZs interacted with the WD-repeat/bHLH/MYB complex to mediate synergism between GA and JA signaling in regulating trichome development. GA and JA induce degradation of DELLAs and JASMONATE ZIM-domain proteins to coordinately activate the WD-repeat/bHLH/MYB complex and synergistically and mutually dependency induce trichome initiation. This study provides deep insights into the molecular mechanisms for integration of different hormonal signals to synergistically regulate plant development.
Plants initiate leaf senescence to relocate nutrients and energy from aging leaves to developing tissues or storage organs for growth, reproduction, and defense. Leaf senescence, the final stage of ...leaf development, is regulated by various environmental stresses, developmental cues, and endogenous hormone signals. Jasmonate (JA), a lipid-derived phytohormone essential for plant defense and plant development, serves as an important endogenous signal to activate senescence-associated gene expression and induce leaf senescence. This study revealed one of the mechanisms underlying JA-induced leaf senescence: antagonistic interactions of the bHLH subgroup IIIe factors MYC2, MYC3, and MYC4 with the bHLH subgroup IIId factors bHLH03, bHLH13, bHLH14, and bHLH17. We showed that MYC2, MYC3, and MYC4 function redundantly to activate JA-induced leaf senescence. MYC2 binds to and activates the promoter of its target gene SAG29 (SENESCENCE-ASSOCIATED GENE29) to activate JA-induced leaf senescence. Interestingly, plants have evolved an elaborate feedback regulation mechanism to modulate JA-induced leaf senescence: The bHLH subgroup IIId factors (bHLH03, bHLH13, bHLH14, and bHLH17) bind to the promoter of SAG29 and repress its expression to attenuate MYC2/MYC3/MYC4-activated JA-induced leaf senescence. The antagonistic regulation by activators and repressors would mediate JA-induced leaf senescence at proper level suitable for plant survival in fluctuating environmental conditions.
Proper stamen development is essential for plants to achieve their life cycles. Defects in stamen development will cause male sterility. A vast array of research efforts have been made to understand ...stamen developmental processes and reg- ulatory mechanisms over the past decades. It is so far reported that phytohormones, including jasmonate, auxin, gibberellin, brassinosteroid, and cytokinin, play essential roles in regulation of stamen development. This review will briefly summarize the molecular basis for coordinated regulation of stamen development by jasmonate, auxin, and gibberellin in Arabidopsis.
The lipid-derived phytohormone jasmonate (JA) regulates plant growth, development, secondary metabolism, defense against insect attack and pathogen infection, and tolerance to abiotic stresses such ...as wounding, UV light, salt, and drought. JA was first identified in 1962, and since the 1980s many studies have analyzed the physiological functions, biosynthesis, distribution, metabolism, perception, signaling, and crosstalk of JA, greatly expanding our knowledge of the hormone’s action. In response to fluctuating environmental cues and transient endogenous signals, the occurrence of multilayered organization of biosynthesis and inactivation of JA, and activation and repression of the COI1–JAZ-based perception and signaling contributes to the fine-tuning of JA responses. This review describes the JA biosynthetic enzymes in terms of gene families, enzymatic activity, location and regulation, substrate specificity and products, the metabolic pathways in converting JA to activate or inactivate compounds, JA signaling in perception, and the co-existence of signaling activators and repressors.
Summary
In response to jasmonates (JAs), the JA receptor Coronatine Insensitive 1 (COI1) recruits JA‐zinc‐finger inflorescence meristem (ZIM)‐domain (JAZ) family repressors for destruction to ...regulate plant growth, development, and defense. As Arabidopsis encodes 13 JAZ repressors, their functional specificity, diversity, and redundancy in JA/COI1‐mediated responses remain unclear.
We generated a broad range of jaz mutants based on their phylogenetic relationship to investigate their roles in JA responses. The group I JAZ6 may play an inhibitory role in resistance to Botrytis cinerea, group II (JAZ10)/III (JAZ11/12) in JA‐regulated root growth inhibition and susceptibility to Pseudomonas syringae pv tomato DC3000, and group IV JAZ3/4/9 in flowering time delay and defense against insects. JAZs exhibit high redundancy in apical hook curvature.
The undecuple jaz1/2/3/4/5/6/7/9/10/11/12 (jaz1‐7,9‐12) mutations enhance JA responses and suppress the phenotypes of coi1‐1 in flowering time, rosette growth, and defense. The JA hypersensitivity of jaz1‐7,9‐12 in root growth, hook curvature, and leaf yellowing is blocked by coi1‐1. jaz1‐7,9‐12 does not influence the stamen phenotypes of wild‐type and coi1‐1. jaz1‐7,9‐12 affects JA‐regulated transcriptional profile and recovers a fraction of that in coi1‐1.
This study contributes to elucidating the specificity, diversity, and redundancy of JAZ members in JA/COI1‐regulated growth, development, and defense responses.
Plants have evolved sophisticated systems for adaptation to their natural habitat. In response to developmental and environmental cues, plants produce and perceive jasmonate (JA) signals, which ...induce degradation of JASMONATE-ZIM-Domain (JAZ) proteins and derepress the JAZ-repressed transcription factors to regulate diverse aspects of defense responses and developmental processes. Here, we identified the bHLH subgroup IIId transcription factors (bHLH3, bHLH13, bHLH14 and bHLH17) as novel targets of JAZs. These bHLH subgroup IIId transcription factors act as transcription repressors and function redundantly to negatively regulate JA responses. The quadruple mutant bhlh3 bhlh13 bhlh14 bhlh17 showed severe sensitivity to JA-inhibited root growth and JA-induced anthocyanin accumulation, and exhibited obvious increase in JA-regulated plant defense against pathogen infection and insect attack. Transgenic plants overexpressing bHLH13 or bHLH17 displayed reduced JA responses. Furthermore, these bHLH factors functioned as transcription repressors to antagonize the transcription activators, such as MYC2 and the WD-repeat/bHLH/MYB complex, through binding to their target sequences. Coordinated regulation of JA responses by transcription activators and repressors would benefit plants by allowing fine regulation of defense and development, and survival in their frequently changing environment.
Jasmonates (JAs), lipid-derived phytohormones, regulate plant growth, development and defenses against biotic stresses. CORONATINE INSENSITIVE1 perceives bioactive JA and recruits JASMONATE ...ZIM-DOMAIN (JAZ) proteins for ubiquitination and subsequent degradation via the 26S proteasome, which de-represses JAZ-targeted transcription factors that regulate diverse JA responses. Recent studies showed that the Arabidopsis basic helix-loop-helix transcription factor MYC5 interacts with JAZs and regulates stamen development. However, whether MYC5 mediates other JA responses is unclear. Here, we show that MYC5 functions redundantly with MYC2, MYC3 and MYC4 to modulate JA-regulated root growth inhibition and plant defenses against insect attack and pathogen infection, and that it positively regulates JA-induced leaf senescence. Our findings define MYC5 as an important regulator that is essential for diverse JA responses.
Gibberellin (GA) and jasmonate (JA) are two essential phytohormones for filament elongation in Arabidopsis. GA and JA trigger degradation of DELLAs and JASMONATE ZIM-domain (JAZ) proteins through SCF
...and SCF
separately to activate filament elongation. In JA pathway, JAZs interact with MYB21 and MYB24 to control filament elongation. However, little is known how DELLAs regulate filament elongation.
Here we showed that DELLAs interact with MYB21 and MYB24, and that R2R3 domains of MYB21 and MYB24 are responsible for interaction with DELLAs. Furthermore, we demonstrated that DELLA and JAZ proteins coordinately repress the transcriptional function of MYB21 and MYB24 to inhibit filament elongation.
We discovered that DELLAs interact with MYB21 and MYB24, and that DELLAs and JAZs attenuate the transcriptional function of MYB21 and MYB24 to control filament elongation. This study reveals a novel cross-talk mechanism of GA and JA in the regulation of filament elongation in Arabidopsis.
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