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Authors: Qunwei Bai, Shurong Xuan, Wenjuan Li, Khawar Ali, Bowen Zheng and Hongyan Ren.
BMC Plant Biology (2024)
Abstract: "Background - Brassinosteroids (BRs) are a class of phytohormones that regulate a wide range of developmental processes in plants. BR-associated mutants display impaired growth and response to developmental and environmental stimuli. Results - Here, we found that a BR-deficient mutant det2-1 displayed abnormal root gravitropic growth in Arabidopsis, which was not present in other BR mutants. To further elucidate the role of DET2 in gravity, we performed transcriptome sequencing and analysis of det2-1 and bri1-116, bri1 null mutant allele. Expression levels of auxin, gibberellin, cytokinin, and other related genes in the two mutants of det2-1 and bri1-116 were basically the same. However, we only found that a large number of JAZ (JASMONATE ZIM-domain) genes and jasmonate synthesis-related genes were upregulated in det2-1 mutant, suggesting increased levels of endogenous JA. Conclusions - Our results also suggested that DET2 not only plays a role in BR synthesis but may also be involved in JA regulation. Our study provides a new insight into the molecular mechanism of BRs on the root gravitropism."
Authors: Yalin Li, Xinyu Yang, Xuewen Li, Chuang Wang, Guangda Ding, Fangsen Xu, Sheliang Wang, Hongmei Cai, John P. Hammond, Sergey Shabala, Min Yu and Lei Shi.
Plant and Soil (2023)
Abstract: "Aims - The aims of this work were to investigate phosphate starvation responses of Brassica napus (B. napus) under heterogeneous phosphate (Pi) supply and the regulatory role of jasmonic acid (JA) in the systemic response to Pi starvation. Methods - A split-root system with two separated compartments was employed to mimic heterogeneous Pi distribution in the soil and to examine the effect of heterogeneous Pi supply, and JA or DIECA (JA biosynthesis inhibitor) on growth, root morphology, Pi concentration, Acid phosphatase (APase) activity, nutrition uptake, JA concentration and expression of Pi starvation systemically-induced (PSSI) genes of B. napus. Results - Heterogeneous Pi supply systemically modified root morphology that increased the total root surface area (TRSA), total root volume (TRV), total root length (TRL) and total lateral root number (TLRN) of root with local Pi supply (R +) and decreased them of root with local no Pi supply (R-) when compared to root with homogeneous Pi supply (R + +) and root devoid of Pi (R–), respectively. Anthocyanin, APase activity and JA concentration in shoot and root of B. napus were systemically regulated by heterogeneous Pi supply. In addition, heterogeneous Pi supply significantly promoted nutrient uptake when compared with homogeneous no Pi supply. Root morphology of B. napus was significantly changed by exogenous addition of JA or DIECA in a split-root system. JA enhanced Pi starvation response by inducing expression of PSSI genes in shoots and roots. Conclusions - Our results suggest that JA enhances systemic Pi starvation response of B. napus by regulating root morphology, Pi homeostasis and inducing expression of PSSI genes under heterogeneous Pi supply."
Authors: Ajit Pal Singh, Rajni Kanwar and Ajay Kumar Pandey.
bioRxiv (2023)
Abstract: "Rhizospheric pH severely impacts plant growth and fitness through a numerous process and has emerged as a major determinant of crop productivity. Despite numerous attempts, the key questions related to plants response against rhizospheric pH remains largely elusive. The present study provides a mechanistic framework for rhizospheric pH-mediated root growth inhibition (RGI). Utilizing various genetic resources combined with pharmacological agents and high-resolution confocal microscopy, the study provides direct evidences for the involvement of jasmonates and auxin in rhizospheric pH-mediated RGI. We show that auxin maxima at root tip is tightly regulated by the rhizospheric pH. In contrast, jasmonates (JAs) abundance inversely correlates with rhizospheric pH. Further, JA mediated regulation of auxin maxima by GRETCHEN HAGEN 3 (GH3) family genes explains the pattern of RGI observed over the entire range of rhizospheric pH. Our findings revealed auxin as the key regulator of RGI during severe pH conditions, while JAs antagonistically regulate auxin response against rhizospheric pH."
Authors: Xinjue Wang, Yumeng Chen, Shuting Liu, Wenjie Fu, Yunqi Zhuang, Jie Xu, Yonggen Lou, Ian T. Baldwin and Ran Li.
New Phytologist (2023)
Abstract: "The phytohormones, jasmonates (JAs), mediate many plant developmental processes and their responses to important environmental stresses, such as herbivore attack. Bioactive JAs are perceived by COI-receptors, and associated JAZ proteins, to activate downstream responses. To date, the JA receptors of the important monocot crop plant, rice, remain to be explored. Here, we studied all 3 rice COI proteins, OsCOI1a, OsCOI1b and OsCOI2, by ligand binding, genome editing and phenotyping and examining some of the responsible mechanisms for the different responses. OsCOI2 binds to most individual OsJAZs in the presence of endogenous JA ligands, as OsCOI1a /1b do, albeit with greater partner selectivity. Single mutants of each OsCOI and OsCOI1a/1b double mutants were constructed by CRISPR-Cas9-based genome editing and used to phenotype developmental and defense responses. OsCOI1b is involved in root growth and grain-size control, and plays overlapping roles with OsCOI1a in spikelet development, while OsCOI2 regulates leaf senescence, male sterility, root growth and grain size. All OsCOIs mediated resistance to the devastating rice pest, the brown planthopper. However, the defense sectors regulated by OsCOI1a/1b and OsCOI2 clearly differed. Our results revealed that all three OsCOIs are functional JA receptors that play diverse roles in regulating downstream JA responses.
Authors: Jiang Zhu, Wen-Shu Wang, Da-Wei Yan, Li-Wei Hong, Ting-Ting Li, Xiang Gao, Yun-Huang Yang, Feng Ren, Ying-Tang Lu and Ting-Ting Yuan.
Nucleic Acids Research (2023)
Abstract: "Jasmonic acid (JA) signaling plays a pivotal role in plant development and defense. MYC2 is a master transcription factor in JA signaling, and was found to be phosphorylated and negatively regulated by MAP kinase and receptor-like kinase. However, the kinases that positively regulate MYC2 through phosphorylation and promote MYC2-mediated activation of JA response have not been identified. Here, we identified CK2 as a kinase that phosphorylates MYC2 and thus regulates the JA signaling. CK2 holoenzyme can interact with MYC2 using its regulatory subunits and phosphorylate MYC2 at multiple sites with its catalytic subunits. Inhibition of CK2 activity in a dominant-negative plant line, CK2mut, repressed JA response. On the other hand, increasing CK2 activity by overexpression of CKB4, a regulatory subunit gene of CK2, enhanced JA response in a MYC2-dependent manner. Substitution of the Ser and Thr residues at phosphorylation sites of MYC2 by CK2 with Ala impaired MYC2 function in activating JA response. Further investigations evidenced that CK2 facilitated the JA-induced increase of MYC2 binding to the promoters of JA-responsive genes in vivo. Our study demonstrated that CK2 plays a positive role in JA signaling, and reveals a previously undiscovered mechanism that regulates MYC2 function."
Authors: Xiao Han, Mengyi Kui, Tingting Xu, Jingwen Ye, Jiancan Du, Milian Yang, Yanjuan Jiang and Yanru Hu.
The Plant Cell (2023)
Abstract: "CONSTANS (CO) is a master flowering-time regulator that integrates photoperiodic and circadian signals in Arabidopsis thaliana. CO is expressed in multiple tissues, including young leaves and seedling roots, but little is known about the roles and underlying mechanisms of CO in mediating physiological responses other than flowering. Here, we show that CO expression is responsive to jasmonate. CO negatively modulated jasmonate-imposed root growth inhibition and anthocyanin accumulation. Seedlings from co mutants were more sensitive to jasmonate, whereas overexpression of CO resulted in plants with reduced sensitivity to jasmonate. Moreover, CO mediated the diurnal gating of several jasmonate-responsive genes under long-day conditions. We demonstrate that CO interacts with JASMONATE ZIM-DOMAIN (JAZ) repressors of jasmonate signaling. Genetic analyses indicated that CO functions in a CORONATINE-INSENSITIVE1 (COI1)-dependent manner to modulate jasmonate responses. Furthermore, CO physically associated with the basic helix-loop-helix (bHLH) subgroup IIId transcription factors bHLH3 and bHLH17. CO acted cooperatively with bHLH17 in suppressing jasmonate signaling, but JAZ proteins interfered with their transcriptional functions and physical interaction. Collectively, our results reveal the crucial regulatory effects of CO on mediating jasmonate responses, and explain the mechanism by which CO works together with JAZ and bHLH subgroup IIId factors to fine-tune jasmonate signaling."
Authors: Xiao Han, Mengyi Kui, Kunrong He, Milian Yang, Jiancan Du, Yanjuan Jiang and Yanru Hu.
Journal of Experimental Botany (2023)
Abstract: "The phytohormone jasmonate is an essential endogenous signal to regulate multiple plant processes for environmental adaptations, such as primary root growth inhibition and root hair elongation. Perception of environmental stresses promotes the accumulation of jasmonate which is sensed by the CORONATINE INSENSITIVE1 (COI1)-JASMONATE ZIM-DOMAIN (JAZ) co-receptor, triggering the degradation of JAZ repressors and induction of transcriptional reprogramming. The basic helix-loop-helix (bHLH) subgroup IIIe transcription factors MYC2, MYC3, and MYC4 are the most extensively characterized JAZ-binding factors and together stimulate jasmonate-signaled primary root growth inhibition. Conversely, the bHLH subgroup IIId transcription factors (i.e. bHLH3 and bHLH17) physically associate with JAZ proteins and suppress jasmonate-induced root growth inhibition. For root hair development, JAZ proteins interact with and inhibit ROOT HAIR DEFECTIVE 6 (RHD6) and RHD6 LIKE1 (RSL1) transcription factors to modulate jasmonate-enhanced root hair elongation. Moreover, jasmonate also interacts with other signaling pathways (such as ethylene and auxin) to regulate primary root growth and/or root hair elongation. Here, we review the recent progresses that have provided insights into jasmonate-mediated primary root growth and root hair development."
Authors: Yalin Li, Xinyu Yang, HaiJiang Liu, Wei Wang, Chuang Wang, Guangda Ding, Fangsen Xu, Sheliang Wang, Hongmei Cai, John P. Hammond, Philip J. White, Sergey Shabala, Min Yu and Lei Shi.
Journal of Experimental Botany (2022)
Abstract: "Due to the non-uniform distribution of inorganic phosphate (Pi) in the soil, plants modify their root architecture to improve acquisition of this nutrient. In this study, a split-root system was employed to assess the nature of local and systemic signals that modulate root architecture of Brassica napus grown with non-uniform Pi availability. Lateral root (LR) growth was regulated systemically by non-uniform Pi distribution, by increasing the second-order LR (2°LR) density in compartments with high Pi supply but decreasing it in compartments with low Pi availability. Transcriptomic profiling identified groups of genes regulated, both locally and systemically, by Pi starvation. The number of systemically induced genes was greater than the number of genes locally induced, and included genes related to abscisic acid (ABA) and jasmonic acid (JA) signalling pathways, reactive oxygen species (ROS) metabolism, sucrose, and starch metabolism. Physiological studies confirmed the involvement of ABA, JA, sugars, and ROS in the systemic Pi starvation response. Our results reveal the mechanistic basis of local and systemic responses of B. napus to Pi starvation and provide new insights into the molecular and physiological basis of root plasticity."
Authors: Mo Chen, Wei Zhang, Mi Yan, Simei He, Yingchun Lu, Guanghui Zhang, Bing Hao, Wei Fan, Yanru Hu and Shengchao Yang.
Plant Molecular Biology Reporter (2022)
Abstract: "The jasmonate ZIM-domain (JAZ) proteins are repressors that function in the regulation of plant growth, development, and response to stimulation of different signals in the JA signaling pathway. Erigeron breviscapus is characteristic of sporophyte self-incompatibility (SSI). However, whether JA signaling is involved in regulation of development processes in E. breviscapus is unclear. In this study, the JAZ homolog EbJAZ1 was isolated and characterized from E. breviscapus. EbJAZ1 was localized to the nucleus, and expressed in roots, stems, leaves and flowers. Ectopic expression of EbJAZ1 in Arabidopsis resulted in shorter filament and silique length, and lower seed fertility. In addition, MeJA-induced root growth inhibition was compromised in transgenic plants. Further qRT-PCR analysis indicated that expression patterns of marker genes for VSP1, VSP2, JAZ1, JAZ5, JAZ8, JAZ10, MYC2, and bHLH17 were downregulated in transgenic plants compared to wild-type, suggesting that EbJAZ regulates the development of flower organs, seed fertility, and primary root growth through the JA signaling pathway. Thus, our results indicate that EbJAZ1 is one of the important regulators possibly involved in SSI and other developmental processes in Erigeron breviscapus."
Authors: Andrea Chini, Isabel Monte, Gemma Fernández-Barbero, Marta Boter, Glenn Hicks, Natasha Raikhel and Roberto Solano.
Plant Physiology (2021)
Abstract: "The phytohormone JA-Ile regulates many stress responses and developmental processes in plants. A co-receptor complex formed by the F-box protein COI1 (Coronatine Insensitive 1) and a JAZ (Jasmonate ZIM-domain) repressor perceives the hormone. JA-Ile antagonists are invaluable tools for exploring the role of JA-Ile in specific tissues and developmental stages, and for identifying regulatory processes of the signalling pathway. Using two complementary chemical screens, we identified three compounds that exhibit a robust inhibitory effect on both the hormone-mediated COI-JAZ interaction and degradation of JAZ1 and JAZ9 in vivo. One molecule, J4, also restrains specific JA-induced physiological responses in different angiosperm plants, including JA-mediated gene expression, growth inhibition, chlorophyll degradation and anthocyanin accumulation. Interaction experiments with purified proteins indicate that J4 directly interferes with the formation of the Arabidopsis (Arabidopsis thaliana) COI1-JAZ complex otherwise induced by JA. The antagonistic effect of J4 on COI1-JAZ also occurs in the liverwort Marchantia polymorpha, suggesting the mode of action is conserved in land plants. Besides JA signalling, J4 works as an antagonist of the closely-related auxin signalling pathway, preventing TIR1/Aux-IAA interaction and auxin responses in planta, including hormone-mediated degradation of an auxin repressor, gene expression and gravitropic response. However, J4 does not affect other hormonal pathways. Altogether, our results show that this dual antagonist competes with JA-Ile and auxin, preventing the formation of phylogenetically related receptor complexes. J4 may be a useful tool to dissect both the JA-Ile and auxin pathways in particular tissues and developmental stages since it reversibly inhibits these pathways."
Authors: Xiao Zou, Li Liu, Zhubing Hu, Xuekui Wang, Yanchun Zhu, Jialiang Zhang, Xuefei Li, Ziyi Kang, Yongjun Lin and Changxi Yin.
Journal of Experimental Botany (2021)
Abstract: "The phytohormones ethylene and jasmonate play important roles in the adaption of rice plants to salt stress. However, the molecular interactions between ethylene and jasmonate on rice seminal root growth under salt stress is unknown. In this study, effects of NaCl on the homeostasis of ethylene and jasmonate and on the rice seminal root growth were investigated. Our results indicate that NaCl treatment promotes ethylene biosynthesis by up-regulating transcription of ethylene biosynthesis genes, whereas NaCl-induced ethylene cannot inhibit rice seminal root growth directly, but rather inhibits growth indirectly by promoting jasmonate biosynthesis. NaCl treatment also promotes jasmonate biosynthesis through an ethylene-independent pathway. Moreover, the analysis results of quantitative real-time PCR and confocal microscopy demonstrate that NaCl-induced jasmonate restricts root meristem cell proliferation by reducing meristem cell number and cell division activity via down-regulated transcription of OsPLT and cell division-related genes, respectively. Additionally, NaCl-induced jasmonate inhibits root cell elongation by down-regulating transcription of cell elongation-related genes, which in turn inhibits seminal root growth. Overall, salt stress promotes jasmonate biosynthesis through ethylene-dependent and -independent pathways in the rice seminal root, and salt-induced jasmonate inhibits the rice seminal root growth by inhibiting root meristem cell proliferation and root cell elongation under salt stress."
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Authors: Shaofang Wu, Chaoyi Hu, Changan Zhu, Yanfen Fan, Jie Zhou, Xiaojia Xia, Kai Shi, Yanhong Zhou, Christine H. Foyer and Jingquan Yu.
Molecular Plant (2024)
Summary: By physically interacting with and ubiquitinating JAZ4, PUB22 functions as a crucial regulator in JA signaling. The degradation of JAZ4 is promoted by PUB22 but not by the classical SCFCOI1. Meanwhile, JA-activated MYC2 promotes the expression of PUB22, establishing a positive regulatory circuit in JA signaling. Our study provides new insights into the regulation of JA signaling through specific PUB.
Abstract: "Jasmonates (JAs), a class of lipid-derived stress hormones, play a crucial role across an array of plant physiological processes and stress responses. While JA signaling is generally thought to rely dominantly on the degradation of specific JASMONATE-ZIM DOMAIN (JAZ) proteins by SCFCOI1, it remains unclear whether other pathways are involved in the regulation of JAZ protein stability. Here, we report that PUB22, a plant U-box type E3 ubiquitin ligase, plays a vital role in the regulation of the resistance against Helicoverpa armigera and other JA responses in tomato. While COI1 physically interacts with JAZ1/2/5/7, PUB22 physically interacts with JAZ1/3/4/6. PUB22 ubiquitinates JAZ4 to promote its degradation via 26S proteasome pathway. Importantly, pub22 mutants had decreased whilst jaz4 mutants and jaz1 jaz3 jaz4 jaz6 quadruple mutants had enhanced resistance against H. armigera. The hypersensitivity to herbivores for pub22 mutants was partially rescued by JAZ4 mutation. Moreover, PUB22 expression was transcriptionally activated by MYC2, thus forming a positive feedback circuit in JA signaling. Notably, the PUB22-JAZ4 module regulated various JA responses, including the defense against Botrytis cinerea, root elongation inhibition and anthocyanin accumulation. Taken together, PUB22 plays a crucial role in plant response to environmental changes in concert with the COI1-regulated JA signaling by targeting specific JAZs."
Authors: Hieu Trang Nguyen, Mohamad Cheaib, Marie Fournel, Maelle Rios, Pascal Gantet, Laurent Laplaze, Soazig Guyomarc’h, Michael Riemann,Thierry Heitz, Anne-Sophie Petitot and Antony Champion.
PLoS ONE (2023)
Abstract: "COI1-mediated perception of jasmonate is critical for plant development and responses to environmental stresses. Monocots such as rice have two groups of COI genes due to gene duplication: OsCOI1a and OsCOI1b that are functionally equivalent to the dicotyledons COI1 and OsCOI2 whose function remains unclear. In order to assess the function of OsCOI2 and its functional redundancy with COI1 genes, we developed a series of rice mutants in the 3 genes OsCOI1a, OsCOI1b and OsCOI2 by CRISPR Cas9-mediated editing and characterized their phenotype and responses to jasmonate. Characterization of OsCOI2 uncovered its important roles in root, leaf and flower development. In particular, we show that crown root growth inhibition by jasmonate relies on OsCOI2 and not on OsCOI1a nor on OsCOI1b, revealing a major function for the non-canonical OsCOI2 in jasmonate-dependent control of rice root growth. Collectively, these results point to a specialized function of OsCOI2 in the regulation of plant development in rice and indicate that sub-functionalisation of jasmonate receptors has occurred in the monocot phylum."
Authors: Naga Jyothi Pullagurla, Supritam Shome, Ranjana Yadav and Debabrata Laha.
bioRxiv (2023)
Abstract: "Jasmonic acid (JA) is a plant hormone that regulates a plethora of physiological processes including immunity and development and is perceived by the F-Box protein, Coronatine-insensitive protein 1(COI1). The discovery of inositol phosphates (InsPs) in the COI1 receptor complex highlights their role in JA perception. InsPs are phosphate-rich signaling molecules that control many aspects of plant physiology. Inositol pyrophosphates (PP-InsPs) are diphosphate containing InsP species of which InsP7 and InsP8 are the best characterized ones. Different InsP and PP-InsP species are linked with JA-related plant immunity. However, role of PP-InsP species in regulating JA-dependent developmental processes are poorly understood. Recent identification of ITPK1 kinase responsible for the production of 5-InsP7 from InsP6 in planta provides a platform to interrogate possible involvement of ITPK-derived InsP species in JA-related plant development. Herein this study, we report that ITPK1-defective plants exhibit increased root growth inhibition to bioactive JA treatment. The itpk1 plants also show increased lateral root density when treated with JA. Notably, JA treatment does not induce ITPK1 protein level. Gene expression analyses revealed that JA-biosynthetic genes are not differentially expressed in the ITPK1-deficient plants. We further demonstrate that genes encoding different JAZ repressor proteins are severely downregulated in the ITPK1-defective plants. Taken together, our study highlights the role of ITPK1 in regulating JA-dependent root architecture development through controlling expression of different JAZ repressor proteins."
Authors: Gilad Gabay, Hanchao Wang, Junli Zhang, Jorge I. Moriconi, German F. Burguener, Leonardo D. Gualano, Tyson Howell, Adam Lukaszewski, Brian Staskawicz, Myeong-Je Cho, Jaclyn Tanaka, Tzion Fahima, Haiyan Ke, Katayoon Dehesh, Guo-Liang Zhang, Jin-Ying Gou, Mats Hamberg, Guillermo E. Santa-María and Jorge Dubcovsky.
Nature Communications (2023)
Editor's view: "Introgression of the short arm of rye chromosome one into common wheat increases root biomass and drought tolerance, but the underlying genetic basis is unknown. Here, the authors report that dosage differences in 12-OXOPHYTODIENOATE REDUCTASE genes modulate the differences of wheat root architecture.
Abstract: "Wheat, an essential crop for global food security, is well adapted to a wide variety of soils. However, the gene networks shaping different root architectures remain poorly understood. We report here that dosage differences in a cluster of monocot-specific 12-OXOPHYTODIENOATE REDUCTASE genes from subfamily III (OPRIII) modulate key differences in wheat root architecture, which are associated with grain yield under water-limited conditions. Wheat plants with loss-of-function mutations in OPRIII show longer seminal roots, whereas increased OPRIII dosage or transgenic over-expression result in reduced seminal root growth, precocious development of lateral roots and increased jasmonic acid (JA and JA-Ile). Pharmacological inhibition of JA-biosynthesis abolishes root length differences, consistent with a JA-mediated mechanism. Transcriptome analyses of transgenic and wild-type lines show significant enriched JA-biosynthetic and reactive oxygen species (ROS) pathways, which parallel changes in ROS distribution. OPRIII genes provide a useful entry point to engineer root architecture in wheat and other cereals."
Authors: Hieu Trang Nguyen, Mohamad Cheaib, Marie Fournel, Maelle Rios, Pascal Gantet, Laurent Laplaze, Soazig Guyomarch, Michael Riemann, Thierry Heitz, Anne-Sophie Petitot and Antony Champion.
bioRxiv (2022)
Abstract: "COI1-mediated perception of jasmonate is critical for plant development and responses to environmental stresses. Monocots such as rice have two groups of COI genes due to gene duplication: OsCOI1a and OsCOI1b that are functionally equivalent to the dicotyledons COI1 on one hand and OsCOI2 whose function remains unclear. In order to assess the function of OsCOI2 and its functional redundancy with COI1 genes, we developed a series of rice mutants in the 3 genes OsCOI1a, OsCOI1b and OsCOI2 by CRISPR Cas9 and characterized their phenotype and responses to jasmonate. Characterization of OsCOI2 uncovered important roles in root, leaf and flower development. In particular, we show that crown root growth inhibition by jasmonate relies on OsCOI2 and not OsCOI1a or OsCOI1b in rice, revealing a major function for the non-canonical OsCOI2 in jasmonate-dependent control of rice root growth. Collectively, these results point to a specialized function of OsCOI2 in the regulation of plant development in rice and indicate that sub-functionalisation of jasmonate receptors has occurred in the monocot phylum."
Authors: Xi Chen, Steven M. Smith, Sergey Shabala and Min Yu.
Journal of Experimental Botany (2023)
Abstract: "Boron (B) is an essential element for plant growth. Many agricultural soils around the globe have either insufficient or excessive amounts of available B, with major implications for crop production. Understanding major limitations imposed by B nutritional disorders may allow breeding crops for improved B use efficiency as well as make them more resilient to excessive B, thus reducing yield penalties. It has become apparent that B-related physiological disorders are mediated in large part by their impact on plant hormonal production and signaling. The aim of this review is to summarize the current knowledge of the roles of hormones in plant responses to B and their impact on plant growth and development. The most significant effect of B deficiency is the inhibition of root elongation. B deficiency promotes the redistribution of auxin in the root elongation zone. Together with cytokinin signals and ethylene, this redistribution and modulation of auxin content triggers inhibition of the root cell elongation. Under B deficiency, root development is also regulated by brassinosteroids and jasmonic acid. Excess B can induce the production of reactive oxygen species (ROS). Abscisic acid and salicylic acid are both produced in response to B toxicity, and both can induce the antioxidant defense system to detoxify ROS. Another adaptation to B toxicity involves changes in the expression levels and activity of aquaporins in roots, thus reducing the uptake of water and delivery of B into the transpiration stream. In addition, abscisic acid mediates stomatal closure to further limit transpiration and the consequent accumulation of B in leaves."
Authors: Gilad Gabay, Hanchao Wang, Junli Zhang, Jorge Moriconi, German F. Burguener, Tyson R Howell, Adam Lukaszewski, Brian Staskawicz, Myeong-Je Cho, Jaclyn Tanaka, Tzion Fahima, Haiyan Ke, Katayoon Dehesh, Guo-Liang Zhang, Jin-Ying Gou, Mats Hamberg, Guillermo Santa Maria and Jorge Dubcovsky.
bioRxiv (2022)
Abstract: "Wheat is an essential crop for global food security and is well adapted to a wide variety of soils. However, the gene networks regulating different root architectures remain poorly understood. We report here the identification of a cluster of a monocot-specific 12-OXOPHYTODIENOATE REDUCTASE genes from subfamily III (OPRIII) that modulate key differences in wheat root architecture associated with grain yield under water-limited conditions. Wheat plants with a loss-of-function mutation in OPRIII showed longer seminal roots, whereas plants with increased OPRIII dosage or transgenic over-expression showed reduced seminal root growth, precocious development of lateral roots and increased jasmonic acid (JA). A JA-biosynthesis inhibitor eliminated the root differences, confirming a JA-mediated mechanism. Multiple transcriptome analysis of transgenic and wild-type lines revealed significant enriched JA-biosynthetic and reactive oxygen species (ROS) pathways that paralleled changes in ROS distribution. The OPRIII genes provide a useful entry point to engineer root architecture in wheat and other cereals."
Authors: Kwi Mi Chung, Agnes J. Demianski, Gregory A. Harrison, Neva Laurie-Berry, Nobutaka Mitsuda and Barbara N. Kunkel.
Journal of Experimental Botany (2022)
Abstract: "Jasmonate (JA) is an important hormone involved in regulating diverse responses to environmental factors as well as growth and development, and its signaling is influenced by other hormones such as ethylene. However, our understanding of the regulatory relationship between the JA and ethylene signaling pathways is limited. In this study, we isolated an Arabidopsis JA-hypersensitive mutant, jah3 (jasmonate hypersensitive3)-1. Our map-based cloning revealed that the JAH3 gene corresponds to At4g16535. JAH3 encodes a protein of unknown function whose amino acid sequence has similarity to leukocyte receptor cluster-like protein. The mutation in jah3-1 is caused by a single nucleotide change from A to T at position 220 of 759 bp. We also generated a second allele, jah3-2, using CRISPR-Cas9, that encodes a truncated protein. Both of these loss-of-function alleles result in hypersensitivity to JA and ethylene-induced root growth inhibition and accelerated dark-induced senescence. Double mutant analyses employing jah3 coi1 and jah3 ein3 demonstrated that the hypersensitive phenotypes of the jah3 mutants are mediated by JA and ethylene signaling components COI1 and EIN3. Therefore, we propose that JAH3 is a negative regulator of both of JA and ethylene signaling."
Authors: Yue Zhang, Bei Liu, Jiaqi Zhai, Qinglei Wang and Susheng Song.
Plant Signaling & Behavior (2021)
Abstract: "The phytohormones jasmonates (JAs) regulate diverse aspects of plant growth and defense responses. The JA-ZIM domain (JAZ) family of repressors are targeted by the JA receptor Coronatine Insensitive 1 for ubiquitination and subsequent degradation via the 26S proteasome. We previously investigated the functions of JAZs in JA responses by analyzing jaz mutants of the phylogenetic group I (jaz1/2/5/6), group II/III (jaz10/11/12), group IV/V (jaz3/4/7/9 and jaz3/4/7/8/9), and their high-order mutant jaz1/2/3/4/5/6/7/9/10/11/12. Here, we examined JA-regulated root growth, apical hook curvature, flowering time, and defense against the insect Spodoptera exigua in the intermediate jaz mutants jaz1/2/5/6/10/11/12, jaz1/2/3/4/5/6/7/9, and jaz3/4/7/8/9/10/11/12. This study shows that these jaz mutants differentially affect JA responses, suggesting the complexity of JA pathway in these multiple jaz mutants."
Authors: Mengjia Zhuang, Chaonan Li, Jingyi Wang, Xinguo Mao, Long Li, Jun Yin, Yan Du, Xiang Wang and Ruilian Jing.
Journal of Experimental Botany (2021)
Abstract: "Root is the unique organ of water and nutrients uptake and sensing environmental stimulus in the soil. The optimization of root system architecture contributes to the stress tolerance and yield improvement. ERF (ETHYLENE RESPONSIVE FACTOR) is one of plant specific transcription factor families associated with various developmental processes and stress tolerance. We cloned a novel ERF transcription factor gene TaSRL1 (SHORT ROOT LENGTH 1) from wheat (Triticum aestivum) which is mainly expressed in root. Ectopic expression of TaSRL1 in rice exhibited short root length and plant height. TaSRL1 regulated expression of genes related to auxin synthesis, transport and signaling. Further studies revealed that TaSRL1 induced expression of the auxin transport gene TaPIN2 by directly binding to its promoter, while the interaction of TaSRL1 and TaTIFY9 repressed TaPIN2 expression. Sequence polymorphisms and association analysis showed that TaSRL1-4A was associated with root depth and angle, plant height and 1000-grain weight of wheat. The haplotype Hap-4A-2 with shallow roots, short plant height and high 1000-grain weight has been positively selected in the Chinese wheat breeding process. Therefore, we demonstrated that TaSRL1 functions as a direct regulator of TaPIN2 in the auxin-dependent pathway, and integrates auxin and JA signaling by interacting with TaTIFY9 to repress root growth. Furthermore, the molecular marker of TaSRL1-4A is valuable for the improvement of root system, plant architecture and yield in wheat breeding process.
Authors: Yupu Huang, Sheliang Wang, Lei Shi and Fangsen Xu.
Journal of Experimental Botany (2021)
Abstract: "Boron (B) is an essential micronutrient for plant growth and development. Jasmonic acid (JA) plays pivotal roles in plant growth. However, the underlying molecular mechanism of JA involvement in B-deficiency-induced root growth inhibition is yet to be explored. In this study, we investigated the response of JA to B deficiency and the mechanism of JAR1-dependent JA signaling in root growth inhibition under B deficiency. B deficiency enhanced JA signaling in roots, and root growth inhibition was partially restored by JA biosynthesis inhibition. jar1-1 (jasmonate-resistant 1, JAR1) mutant, mutants of coronatine-insensitive 1 (coi1-2) and myc2 defective in JA signaling showed insensitivity to B deficiency. Ethylene-overproduction mutant eto1 and ethylene-insensitive mutant etr1 showed sensitivity and insensitivity to B deficiency, respectively, suggesting that ethylene is involved in the inhibition of primary root growth under B deficiency. Furthermore, after a declined in EIN3 protein levels, which may contribute to root growth, ethylene signaling was weakened in the jar1-1 mutant root under B deficiency. Under B deficiency, B concentrations were increased in the roots and shoots of the jar1-1 mutant, owing to the large root system and its activity. Therefore, our findings revealed that JA, which is involved in the inhibition of root growth under B deficiency, is regulated by JAR1 activated JA and ethylene signaling pathways."
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