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Author: Leiyun Yang
The Plant Cell (2024)
Excerpts: "Simultaneously, low temperature stimulates plant immunity by activating salicylic acid (SA)-mediated signaling (Wu et al. 2019). However, the mechanism by which plants integrate cold signals and immune signaling remain elusive. To investigate this question, Shaoqin Li and colleagues (Li et al. 2024) studied the potential involvement of ICE1 in cold-induced immunity in Arabidopsis."
"To elucidate how ICE1 regulates cold-induced immunity, the authors conducted a yeast-two-hybrid screen and identified NON-EXPRESSER OF PR GENES 1 (NPR1), a master transcriptional co-activator of PATHOGENESIS-RELATED GENE 1 (PR1) in SA-activated immunity, as an ICE1 interactor.....Additionally, the authors found that ICE1 directly binds to the PR1 promoter for gene activation. These results illustrate that ICE1 interacts with NPR1 and is required for SA-mediated immunity by directly promoting PR1 expression."
"These results support the conclusion that ICE1 and TGA3 work synergistically to promote PR1 transcription. This study not only shed light on a new role of ICE1 in SA-mediated immunity at low temperature, but also revealed NPR1-TGA3/ICE1 as an important nexus integrating SA signaling and cold signals in plant immunity (see Figure)."
Authors: Yexing Jing, Ziyi Yang, Zongju Yang, Wanqing Bai, Ruizhen Yang, Yanjun Zhang, Kewei Zhang, Yunwei Zhang and Jiaqiang Sun.
New Phytologist (2024)
Abstract: "Leaf senescence is a complex process strictly regulated by various external and endogenous factors. However, the key signaling pathway mediating leaf senescence remains unknown. Here, we show that Arabidopsis SPX1/2 negatively regulate leaf senescence genetically downstream of the strigolactone (SL) pathway. We demonstrate that the SL receptor AtD14 and MAX2 mediate the age-dependent degradation of SPX1/2. Intriguingly, we uncover an age-dependent accumulation of SLs in leaves via transcriptional activation of SL biosynthetic genes by the transcription factors (TFs) SPL9/15. Furthermore, we reveal that SPX1/2 interact with the WRKY75 subclade TFs to inhibit their DNA-binding ability and thus repress transcriptional activation of salicylic acid (SA) biosynthetic gene SA Induction-Deficient 2, gating the age-dependent SA accumulation in leaves at the leaf senescence onset stage. Collectively, our new findings reveal a signaling pathway mediating sequential activation of SL and salicylate biosynthesis for the onset of leaf senescence in Arabidopsis."
Authors: Lin Meng, Haipo Yang, Jinli Yang, Yaping Wang, Tiantian Ye, Lin Xiang, Zhulong Chan and Yanping Wang.
Journal of Experimental Botany (2024)
Abstract: "WRKY transcription factors (TFs) play a central role in controlling plant organ senescence. However, it is unclear whether and how WRKY TFs regulate petal senescence in tulip, a widely used ornamental plant. In the present study, we report that TgWRKY75 promoted petal senescence by enhancing abscisic acid (ABA) as well as salicylic acid (SA) synthesis in tulip and in Arabidopsis. The expression level of TgWRKY75 was up-regulated in senescent petals and exogenous ABA or SA treatment induced its expression. The endogenous contents of ABA and SA significantly increased during petal senescence or depended upon TgWRKY75 overexpression. Interestingly, two SA synthesis-related genes TgICS1 and TgPAL1 were identified as direct targets of TgWRKY75 through binding to their promoters. In parallel, TgWRKY75 activated the expression of ABA biosynthesis-related gene TgNCED3 via directly binding to its promoter region. Site mutation of the W-box core motif located on the promoters of TgICS1, TgPAL1 and TgNCED3 eliminated their interactions with TgWRKY75. In summary, this study demonstrated a dual regulation of ABA and SA biosynthesis by TgWRKY75, which unveiled a synergistic process of tulip petal senescence through a feedback regulation between TgWRKY75 and ABA/SA accumulation."
Authors: Raul Zavaliev and Xinnian Dong.
Molecular Cell (2024)
Abstract: "Nonexpressor of pathogenesis-related genes 1 (NPR1) was discovered in Arabidopsis as an activator of salicylic acid (SA)-mediated immune responses nearly 30 years ago. How NPR1 confers resistance against a variety of pathogens and stresses has been extensively studied; however, only in recent years have the underlying molecular mechanisms been uncovered, particularly NPR1’s role in SA-mediated transcriptional reprogramming, stress protein homeostasis, and cell survival. Structural analyses ultimately defined NPR1 and its paralogs as SA receptors. The SA-bound NPR1 dimer induces transcription by bridging two TGA transcription factor dimers, forming an enhanceosome. Moreover, NPR1 orchestrates its multiple functions through the formation of distinct nuclear and cytoplasmic biomolecular condensates. Furthermore, NPR1 plays a central role in plant health by regulating the crosstalk between SA and other defense and growth hormones. In this review, we focus on these recent advances and discuss how NPR1 can be utilized to engineer resistance against biotic and abiotic stresses."
Authors: Qian Gong, Yunjing Wang, Linfang He, Fan Huang, Danfeng Zhang, Yan Wang, Xiang Wei, Meng Han, Haiteng Deng, Lan Luo, Feng Cui, Yiguo Hong and Yule Liu.
Nature (2023)
Editor's view: Aphid-transmitted viruses encode proteins that suppress the plant airborne defence response—which is triggered by volatile chemicals released by neighbouring plants after aphid attack—and the plants consequently become less repellent to aphids and more suitable for aphid survival, infestation and viral transmission.
Abstract: "Aphids transmit viruses and are destructive crop pests1. Plants that have been attacked by aphids release volatile compounds to elicit airborne defence (AD) in neighbouring plants2–5. However, the mechanism underlying AD is unclear. Here we reveal that methyl-salicylate (MeSA), salicylic acid-binding protein-2 (SABP2), the transcription factor NAC2 and salicylic acid-carboxylmethyltransferase-1 (SAMT1) form a signalling circuit to mediate AD against aphids and viruses. Airborne MeSA is perceived and converted into salicylic acid by SABP2 in neighbouring plants. Salicylic acid then causes a signal transduction cascade to activate the NAC2–SAMT1 module for MeSA biosynthesis to induce plant anti-aphid immunity and reduce virus transmission. To counteract this, some aphid-transmitted viruses encode helicase-containing proteins to suppress AD by interacting with NAC2 to subcellularly relocalize and destabilize NAC2. As a consequence, plants become less repellent to aphids, and more suitable for aphid survival, infestation and viral transmission. Our findings uncover the mechanistic basis of AD and an aphid–virus co-evolutionary mutualism, demonstrating AD as a potential bioinspired strategy to control aphids and viruses."
Authors: Shaoqin Li, Yongping Yang, Li He, Xiao Han, Yanru Hu and Yanjuan Jiang.
bioRxiv (2023)
Abstract: "Cold stress affects plant immune responses, and this process may involve the salicylic acid (SA) signaling pathway. However, the underlying mechanism by which low temperature signals coordinate with SA signaling to regulate plant immunity remains poorly characterized. Here, we found that low temperatures enhanced the disease resistance of Arabidopsis against Pseudomonas syringae pv. tomato (Pst) DC3000. This process required Inducer of CBF expression 1 (ICE1), the core transcription factor in cold-signal cascades. ICE1 physically interacted with Non-expresser of PR genes 1 (NPR1), the master regulator of the SA signaling pathway. Enrichment of ICE1 on the PR1 promoter and its ability to transcriptionally activate PR1 were enhanced by NPR1. Further analyses revealed that cold stress signals cooperate with SA signals to facilitate plant immunity against pathogen attack in an ICE1-dependent manner. Cold treatment promoted interactions of NPR1 and TGA3 with ICE1, and increased the ability of the ICE1-TGA3 complex to transcriptionally activate PR1. Together, our results characterize a previously unrecognized role of ICE1 as an indispensable regulatory node linking low temperature activated- and SA-regulated immunity. Discovery of a crucial role of ICE1 in coordinating multiple signals associated with immunity broadens our understanding of plant-pathogen interactions."
Authors: Muhammad Saad Shoaib Khan, Sulaiman Ahmed, Aziz ul Ikram, Fakhir Hannan, Muhammad Umair Yasin, Jin Wang, Biying Zhao, Faisal Islam and Jian Chen.
Physiologia Plantarum (2023)
Highlights: • Melatonin acts as a redox network regulator in plants via regulating secondary messengers signaling. • Melatonin regulates the activity of redox-sensitive proteins and transcription factors. • Melatonin influences gene expression and physiological processes in response to stresses. • Melatonin synergically work with other hormones to confer plant resistance and stress adaptability.
Abstract: "Plants being sessile in nature, are exposed to unwarranted threats as a result of constantly changing environmental conditions. These adverse factors can have negative impacts on their growth, development, and yield. Hormones are key signaling molecules enabling cells to respond rapidly to different external and internal stimuli. In plants, melatonin (MT) plays a critical role in the integration of various environmental signals and activation of stress-response networks to develop defense mechanisms and plant resilience. Additionally, melatonin can tackle the stress-induced alteration of cellular redox equilibrium by regulating the expression of redox homeostasis-related genes and proteins. The purpose of this article is to compile and summarize the scientific research pertaining to MT's effects on plants' resilience to biotic and abiotic stresses. Here, we have summarized that MT exerts a synergistic effect with other phytohormones, for instance, ethylene, jasmonic acid, and salicylic acid, and activates plant defense-related genes against phytopathogens. Furthermore, MT interacts with secondary messengers like Ca2+, nitric oxide, and reactive oxygen species to regulate the redox network. This interaction triggers different transcription factors to alleviate stress-related responses in plants. Hence, the critical synergic role of MT with diverse plant hormones and secondary messengers demonstrates phytomelatonin's importance in influencing multiple mechanisms to contribute to plant resilience against harsh environmental factors."
Authors: Hehong Zhang, Fengmin Wang, Weiqi Song, Zihang Yang, Lulu Li, Qiang Ma, Xiaoxiang Tan, Zhongyan Wei, Yanjun Li, Junmin Li, Fei Yan, Jianping Chen and Zongtao Sun.
Nature Communications (2023)
Editor's view: Plant viruses have evolved various virulence strategies to overcome plant immunity. Here the authors show that distinct viral proteins repress JA-SA crosstalk by targeting rice NPR1 protein to facilitate viral infection
Abstract: "Salicylic acid (SA) and jasmonic acid (JA) are plant hormones that typically act antagonistically in dicotyledonous plants and SA and JA signaling is often manipulated by pathogens. However, in monocotyledonous plants, the detailed SA-JA interplay in response to pathogen invasion remains elusive. Here, we show that different types of viral pathogen can disrupt synergistic antiviral immunity mediated by SA and JA via OsNPR1 in the monocot rice. The P2 protein of rice stripe virus, a negative-stranded RNA virus in the genus Tenuivirus, promotes OsNPR1 degradation by enhancing the association of OsNPR1 and OsCUL3a. OsNPR1 activates JA signaling by disrupting the OsJAZ-OsMYC complex and boosting the transcriptional activation activity of OsMYC2 to cooperatively modulate rice antiviral immunity. Unrelated viral proteins from different rice viruses also interfere with the OsNPR1-mediated SA-JA interplay to facilitate viral pathogenicity, suggesting that this may be a more general strategy in monocot plants. Overall, our findings highlight that distinct viral proteins convergently obstruct JA-SA crosstalk to facilitate viral infection in monocot rice."
Authors: Lei Xu, Hongyu Zhao, Junbin Wang, Xuming Wang, Xianqing Jia, Long Wang, Zhuang Xu, Ruili Li, Kun Jiang, Zhixiang Chen, Jie Luo, Xiaodong Xie and Keke Yi.
New Phytologist (2023)
Abstract: "● The basal levels of salicylic acid (SA) vary dramatically among plant species. In the shoot, for example, rice contains almost 100 times higher SA levels than Arabidopsis. Despite its high basal levels, neither the biosynthetic pathway nor the biological functions of SA are well understood in rice. ● Combining with metabolites analysis, physiological, and genetic approaches, we found that the synthesis of basal SA in rice shoot is dependent on OsAIM1, which encodes a beta-oxidation enzyme in the phenylalanine ammonia-lyase (PAL) pathway. ● Compromised SA accumulation in the Osaim1 mutant led to a lower shoot temperature than wild-type plants. However, this shoot temperature defect resulted from increased transpiration due to elevated steady-state stomatal aperture in the mutant. Furthermore, the high basal SA level is required for sustained expression of OsWRKY45 to modulate the steady-state stomatal aperture and shoot temperature in rice. ● Taken together, these results provide the direct genetic evidence for the critical role of the PAL pathway in the biosynthesis of high basal level SA in rice, which plays an important role in the regulation of steady-state stomatal aperture to promote fitness under stress conditions."
Authors: Ningkun Liu, Yanzhuo Xu, Qi Li, Yuxin Cao, Dechang Yang, Shasha Liu, Xiaokang Wang, Yingjie Mi, Yang Liu, Chenxi Ding, Yan Liu, Yong Li, Yao-Wu Yuan, Ge Gao, Jinfeng Chen, Weiqiang Qian and Xiaoming Zhang.
Cell Host & Microbe (2022)
Editor's view: Liu et al. discover a lncRNA in Arabidopsis as a key regulator balancing immunity and growth. The lncRNA fine-tunes salicylic acid (SA) biosynthesis through regulating the expression of a neighboring transcription factor that controls SA biosynthesis. Expression of the lncRNA decreases upon pathogen infection, leading to derepression of immunity.
Highlights: • lncRNA SABC1 suppresses immunity and promotes growth in healthy plants • SABC1 represses the transcription factor NAC3 in cis • NAC3 activates expression of the SA biosynthesis enzyme ICS1 • Pathogen infection decreases SABC1 expression leading to derepression of immunity
Abstract: "Constitutive activation of plant immunity is detrimental to plant growth and development. Here, we uncover the role of a long non-coding RNA (lncRNA) in fine-tuning the balance of plant immunity and growth. We find that a lncRNA termed salicylic acid biogenesis controller 1 (SABC1) suppresses immunity and promotes growth in healthy plants. SABC1 recruits the polycomb repressive complex 2 to its neighboring gene NAC3, which encodes a NAC transcription factor, to decrease NAC3 transcription via H3K27me3. NAC3 activates the transcription of isochorismate synthase 1 (ICS1), a key enzyme catalyzing salicylic acid (SA) biosynthesis. SABC1 thus represses SA production and plant immunity via decreasing NAC3 and ICS1 transcriptions. Upon pathogen infection, SABC1 is downregulated to derepress plant resistance to bacteria and viruses. Together, our findings reveal lncRNA SABC1 as a molecular switch in balancing plant defense and growth by modulating SA biosynthesis."
Authors: Qinglong Dong, Dingyue Duan, Wenqian Zheng, Dong Huang, Qian Wang, Xiaoran Li, Ke Mao and Fengwang Ma.
Horticulture Research (2021)
Abstract: "High temperature (HT) is one of the most important environmental stress factors and seriously threatens plant growth, development, and production. VQ motif-containing proteins are transcriptional regulators that have been reported to regulate plant growth and developmental processes, including responses to biotic and abiotic stresses. However, the relationships between VQ motif-containing proteins and HT stress have not been studied in depth in plants. In this study, transgenic apple (Malus domestica) plants overexpressing the apple VQ motif-containing protein-coding gene (MdVQ37) were exposed to HT stress, and the transgenic lines exhibited a heat-sensitive phenotype. In addition, physiological and biochemical studies revealed that, compared with WT plants, transgenic lines had lower enzymatic activity and photosynthetic capacity and lower amounts of nonenzymatic antioxidant system metabolites under HT stress. Transcriptome analysis revealed 1379 genes whose expression differed between the transgenic lines and WT plants. GO and KEGG pathway analyses showed that transcription factor activity and plant hormone signaling pathways were differentially influenced and enriched in the transgenic lines. Salicylic acid (SA) content analysis indicated that overexpression of MdVQ37 reduced the content of endogenous SA by regulating the expression of SA catabolism-related genes, which ultimately resulted in disruption of the SA-dependent signaling pathway under HT stress. The application of SA slightly increased the survival rate of the transgenic lines under HT stress. Taken together, our results indicate that apple MdVQ37 has a regulatory function in basal thermotolerance by modulating the activity of transcription factors and SA homeostasis. Overall, this study provides novel insights that improve our understanding of the various functions of VQ motif-containing proteins."
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Authors: Shaoqin Li, Li He, Yongping Yang, Yixin Zhang, Xiao Han, Yanru Hu and Yanjuan Jiang.
The Plant Cell (2024)
One-sentence summary: The NPR1–TGA3–ICE1 regulatory module represents an important step in salicylic acid signaling during cold-activated resistance of plants to pathogen attack.
Abstract: "Cold stress affects plant immune responses, and this process may involve the salicylic acid (SA) signaling pathway. However, the underlying mechanism by which low-temperature signals coordinate with SA signaling to regulate plant immunity remains unclear. Here, we found that low temperatures enhanced the disease resistance of Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000. This process required INDUCER OF CBF EXPRESSION 1 (ICE1), the core transcription factor in cold-signal cascades. ICE1 physically interacted with NONEXPRESSER OF PATHOGENESIS-RELATED GENES 1 (NPR1), the master regulator of the SA signaling pathway. Enrichment of ICE1 on the PATHOGENESIS-RELATED GENE 1 (PR1) promoter and its ability to transcriptionally activate PR1 were enhanced by NPR1. Further analyses revealed that cold stress signals cooperate with SA signals to facilitate plant immunity against pathogen attack in an ICE1-dependent manner. Cold treatment promoted interactions of NPR1 and TGACG-BINDING FACTOR 3 (TGA3) with ICE1 and increased the ability of the ICE1–TGA3 complex to transcriptionally activate PR1. Together, our results characterize a critical role of ICE1 as an indispensable regulatory node linking low-temperature-activated and SA-regulated immunity. Understanding this crucial role of ICE1 in coordinating multiple signals associated with immunity broadens our understanding of plant–pathogen interactions."
Authors: Weiwei Cai, Yilin Tao, Xingge Cheng, Meiyun Wan, Jianghuang Gan, Sheng Yang, Thomas W. Okita, Shuilin He and Li Tian.
Plant Biotechnology Journal (2024)
Abstract: "To challenge the invasion of various pathogens, plants re-direct their resources from plant growth to an innate immune defence system. However, the underlying mechanism that coordinates the induction of the host immune response and the suppression of plant growth remains unclear. Here we demonstrate that an auxin response factor, CaARF9, has dual roles in enhancing the immune resistance to Ralstonia solanacearum infection and in retarding plant growth by repressing the expression of its target genes as exemplified by Casmc4, CaLBD37, CaAPK1b and CaRROP1. The expression of these target genes not only stimulates plant growth but also negatively impacts pepper resistance to R. solanacearum. Under normal conditions, the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 is active when promoter-bound CaARF9 is complexed with CaIAA2. Under R. solanacearum infection, however, degradation of CaIAA2 is triggered by SA and JA-mediated signalling defence by the ubiquitin-proteasome system, which enables CaARF9 in the absence of CaIAA2 to repress the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 and, in turn, impeding plant growth while facilitating plant defence to R. solanacearum infection. Our findings uncover an exquisite mechanism underlying the trade-off between plant growth and immunity mediated by the transcriptional repressor CaARF9 and its deactivation when complexed with CaIAA2."
Authors: Jordan Powers, Xing Zhang, Andres V. Reyes, Raul Zavaliev, Shou-Ling Xu and Xinnian Dong.
bioRxiv (2024)
Abstract: "For over 60 years, salicylic acid (SA) has been known as a plant immune signal required for both basal and systemic acquired resistance (SAR). SA activates these immune responses by reprogramming up to 20% of the transcriptome through the function of NPR1. However, components in the NPR1-signaling hub, which appears as nuclear condensates, and the NPR1-signaling cascade remained elusive due to difficulties in studying transcriptional cofactors whose chromatin associations are often indirect and transient. To overcome this challenge, we applied TurboID to divulge the NPR1-proxiome, which detected almost all known NPR1-interactors as well as new components of transcription-related complexes. Testing of new components showed that chromatin remodeling and histone demethylation contribute to SA-induced resistance. Globally, NPR1-proxiome shares a striking similarity to GBPL3-proxiome involved in SA synthesis, except associated transcription factors (TFs), suggesting that common regulatory modules are recruited to reprogram specific transcriptomes by transcriptional cofactors, like NPR1, through binding to unique TFs. Stepwise greenCUT&RUN analyses showed that, upon SA-induction, NPR1 initiates the transcriptional cascade primarily through association with TGA TFs to induce expression of secondary TFs, predominantly WRKYs. WRKY54 and WRKY70 then play a major role in inducing immune-output genes without interacting with NPR1 at the chromatin. Moreover, a loss of NPR1 condensate formation decreases its chromatin-association and transcriptional activity, indicating the importance of condensates in organizing the NPR1-signaling hub and initiating the transcriptional cascade. This study demonstrates how combinatorial applications of TurboID, and stepwise greenCUT&RUN transcend traditional genetic methods to globally map signaling hubs and transcriptional cascades."
Authors: Mikayla Carty, Ruize Zhang, Ziyue Li, Daowen Wang and Zheng Qing Fu.
Molecular Plant (2023)
Excerpts: "Aphids are highly destructive pests that greatly hurt the agricultural industry. Transmitting over 40% of plant viruses, they are the most destructive pests that the agricultural industry faces (Gong et al., 2023). Aphids feed on plants, and in doing so, they consume sap from one plant and then move to another and inject their saliva into the new plant (Hooks and Fereres, 2006). This cycle causes diseases and viral pathogens to become rampant between plants as the aphids carry viral pathogens from one plant to another and so on. In response to this harmful process, plants release volatile organic compounds (VOCs) in order to elicit airborne defense (AD) mechanisms to counterstrike harmful aphids and aphid-transmitted viruses (Hooks and Fereres, 2006). A fascinating recent study published from Yule Liu’s lab revealed that methyl-salicylate (MeSA) serves as a VOC in the AD battle against aphids and viruses (Gong et al., 2023).
"Gong et al. discovered that phloem-feeding insects like aphids trigger a SA response in attacked plants, leading to an increase in SA levels (Gong et al., 2023). This SA increase activates the NAC2 transcription factor, which in turn binds to the SAMT1 promoter and induces the transcription of SAMT1, encoding the enzyme responsible for converting SA into MeSA (Figure 1A). This marks the start of the AD process. MeSA, as a predominant VOC induced by aphid attacks, will then reach the neighboring plants (Gong et al., 2023)."
"In response to this plant adaptation, some aphid-transmitted viruses have evolved mechanisms to suppress MeSA emission in aphid-attacked plants, impairing the induction of plant defenses against virus infection and aphid infestation in nearby plants and therefore effectively fighting against AD. This is accomplished through helicase-domain-containing proteins that interfere with NAC2. For example, CMV1a interacts with NAC2 and promotes NAC2 degradation through the 26S proteasome, disrupting the process that produces AD-inducing MeSA (Figure 1B) (Gong et al., 2023)."
Authors: Shan Liu, Faisal Islam, Jianping Chen, Zongtao Sun and Jian Chen.
Plant Communications (2024)
Excerpts: "Plants have evolved to generate and release a wide array of volatile organic compounds (VOCs) when challenged by environmental stimuli such as biotic and abiotic stresses, which facilitate their reproduction, defense responses, and plant-plant communication (Karban, 2021). Once emitted, some VOCs can elicit defense signaling in neighboring plants by interacting with specific receptor(s), a phenomenon referred to as airborne defense (AD) (Loreto and D’Auria, 2022)."
"MeSA plays important roles in plant AD. However, the mode of action of MeSA bridging interplant communication and inducing plant AD remains unclear. The recent study of Gong et al. (2023) unveiled an integral MeSA-mediated AD signal circuit composed of MeSA, salicylic acid-binding protein-2 (SABP2), the transcription factor NAC2, and salicylic acid-carboxylmethyltransferase-1 (SAMT1). This investigation deciphers the details of the molecular genetic mechanism by which MeSA is generated and perceived by neighboring plants as a plant AD agent (Gong et al., 2023)."
"In the interplay of aphid-plant-virus, aphid attack induces a high level of SA in plants, which activates NAC2-modulated SAMT1 transcription, thus upregulating biosynthesis and volatilization of MeSA, and conferring plant SAR against viruses (Figure 1A). As an airborne signal, volatile MeSA disperses and is then perceived by neighboring plants through the odorant-binding protein-like receptor SABP2, which converts MeSA into SA, leading to NAC2–SAMT1 activation to produce more MeSA against aphid infestation (Figure 1A). To counteract plant AD, CMV deploys a helicase domain-containing protein, possibly a conserved tactic among multiple virus species, to relocate and degrade NAC2 and thus promote aphid survival and virus infection by undermining the MeSA–SABP2–NAC2–SAMT1 signaling cascade (Figure 1B).
Authors: Lijun Cao, Heejin Yoo, Tianyuan Chen, Musoki Mwimba, Xing Zhang and Xinnian Dong.
bioRxiv (2023)
Abstract: "In plants, a local infection can lead to systemic acquired resistance (SAR) through increased production of salicylic acid (SA). For 30 years, the identity of the mobile signal and its direct transduction mechanism for systemic SA synthesis in initiating SAR have been hotly debated. We found that, upon pathogen challenge, the cysteine residue of transcription factor CHE undergoes sulfenylation in systemic tissues, enhancing its binding to the promoter of SA-synthesis gene, ICS1, and increasing SA production. This occurs independently of previously reported pipecolic acid (Pip) signal. Instead, H2O2 produced by NADPH oxidase, RBOHD, is the mobile signal that sulfenylates CHE in a concentration-dependent manner. This modification serves as a molecular switch that activates CHE-mediated SA-increase and subsequent Pip-accumulation in systemic tissues to synergistically induce SAR."
Authors: Jingjing Luo, Wenying Yu, Yuansong Xiao, Yafei Zhang and Futian Peng.
Horticultural Plant Journal (2024)
Abstract: "Strawberry is a major fruit crop worldwide because its nutritional and health benefits to human health, but its productivity is limited by Botrytis cinerea. Sucrose nonfermentation 1-related protein kinase 1 (SnRK1) has a defense function against pathogens, but the function of SnRK1 in the defense response to B. cinerea in plants is still unclear. In this study, FaSnRK1α-OE and RNAi fruits were constructed and then inoculated with B. cinerea. The result reveals a positive role of FaSnRK1α in the regulation of resistance to gray mold. FaSnRK1α affects SA content by regulating FaPAL1 and FaPAL2 expressions. The genes related to the SA signaling pathway (FaTGA1 and FaTGA2.1) were significantly increased/decreased in FaSnRK1α-OE or FaSnRK1α-RNAi fruit, respectively. FaSnRK1α interacted with the FaWRKY33.2 protein and negatively regulated FaWRKY33.2 expression, and FaWRKY33.2 acts as a repressor of disease resistance to B. cinerea. Finally, FaSnRK1α regulates the expression of six PR genes and the activities of antioxidant enzymes to boost defense response after B. cinerea inoculation. Our findings showed that FaSnRK1α increases the resistance of strawberry fruit to B. cinerea via SA signaling pathway and interaction with the FaWRKY33.2 transcription factor."
Authors: Lingling Yin, Mark Zander, Shao-shan Carol Huang, Mingtang Xie, Liang Song, J. Paola Saldierna Guzmán, Elizabeth Hann, Bhuvana K. Shanbhag, Sophia Ng, Siddhartha Jain, Bart J. Janssen, Natalie M. Clark, Justin Walley, Travis Beddoe, Ziv Bar-Joseph,Mathew G. Lewsey and Joseph R. Ecker.
bioRxiv (2023)
Abstract: "Cross-regulation between hormone signaling pathways is indispensable for plant growth and development. However, the molecular mechanisms by which multiple hormones interact and co-ordinate activity need to be understood. Here, we generated a cross-regulation network explaining how hormone signals are integrated from multiple pathways in etiolated Arabidopsis (Arabidopsis thaliana) seedlings. To do so we comprehensively characterized transcription factor activity during plant hormone responses and reconstructed dynamic transcriptional regulatory models for six hormones; abscisic acid, brassinosteroid, ethylene, jasmonic acid, salicylic acid and strigolactone/karrikin. These models incorporated target data for hundreds of transcription factors and thousands of protein-protein interactions. Each hormone recruited different combinations of transcription factors, a subset of which were shared between hormones. Hub target genes existed within hormone transcriptional networks, exhibiting transcription factor activity themselves. In addition, a group of MITOGEN-ACTIVATED PROTEIN KINASES (MPKs) were identified as potential key points of cross-regulation between multiple hormones. Accordingly, the loss of function of one of these (MPK6) disrupted the global proteome, phosphoproteome and transcriptome during hormone responses. Lastly, we determined that all hormones drive substantial alternative splicing that has distinct effects on the transcriptome compared with differential gene expression, acting in early hormone responses. These results provide a comprehensive understanding of the common features of plant transcriptional regulatory pathways and how cross-regulation between hormones acts upon gene expression."
Authors: Shuangcheng He, Fang Zhi, Yuanchang Min, Rong Ma, Ankang Ge, Shixiang Wang, Jianjun Wang, Zijin Liu, Yuan Guo and Mingxun Chen.
Plant Physiology (2023)
Abstract: "Leaf senescence is the final stage of leaf development and is affected by various exogenous and endogenous factors. Transcriptional regulation is essential for leaf senescence, however, the underlying molecular mechanisms remain largely unclear. In this study, we report that the transcription factor MYB59, which was predominantly expressed in early senescent rosette leaves, negatively regulates leaf senescence in Arabidopsis (Arabidopsis thaliana). RNA sequencing revealed a large number of differentially expressed genes involved in several senescence-related biological processes in myb59-1 rosette leaves. Chromatin immunoprecipitation and transient dual-luciferase reporter assays demonstrated that MYB59 directly repressed the expression of SENESCENCE ASSOCIATED GENE 18 and indirectly inhibited the expression of several other senescence-associated genes to delay leaf senescence. Moreover, MYB59 was induced by salicylic acid (SA) and jasmonic acid (JA). MYB59 inhibited SA production by directly repressing the expression of ISOCHORISMATE SYNTHASE 1 and PHENYLALANINE AMMONIA-LYASE 2 and restrained JA biosynthesis by directly suppressing the expression of LIPOXYGENASE 2, thus forming two negative feedback regulatory loops with SA and JA and ultimately delaying leaf senescence. These results help us understand the novel function of MYB59 and provide insights into the regulatory network controlling leaf senescence in A. thaliana."
Authors: Jong Hum Kim, Christian Danve M. Castroverde, Shuai Huang, Chao Li, Richard Hilleary, Adam Seroka, Reza Sohrabi, Diana Medina-Yerena, Bethany Huot, Jie Wang, Kinya Nomura, Sharon K. Marr, Mary C. Wildermuth, Tao Chen, John D. MacMicking and Sheng Yang He.
Nature (2022)
Editor's view: Suppression of salicylic acid production in Arabidopsis thaliana at high temperature is caused by decreased recruitment of GUANYLATE BINDING PROTEIN-LIKE 3 defence-associated condensates on promoter sites of master immune regulatory genes.
Abstract: "Extreme weather conditions associated with climate change affect many aspects of plant and animal life, including the response to infectious diseases. Production of salicylic acid (SA), a central plant defence hormone1–3, is particularly vulnerable to suppression by short periods of hot weather above the normal plant growth temperature range via an unknown mechanism4–7. Here we show that suppression of SA production in Arabidopsis thaliana at 28 °C is independent of PHYTOCHROME B8,9 (phyB) and EARLY FLOWERING 310 (ELF3), which regulate thermo-responsive plant growth and development. Instead, we found that formation of GUANYLATE BINDING PROTEIN-LIKE 3 (GBPL3) defence-activated biomolecular condensates11 (GDACs) was reduced at the higher growth temperature. The altered GDAC formation in vivo is linked to impaired recruitment of GBPL3 and SA-associated Mediator subunits to the promoters of CBP60g and SARD1, which encode master immune transcription factors. Unlike many other SA signalling components, including the SA receptor and biosynthetic genes, optimized CBP60g expression was sufficient to broadly restore SA production, basal immunity and effector-triggered immunity at the elevated growth temperature without significant growth trade-offs. CBP60g family transcription factors are widely conserved in plants12. These results have implications for safeguarding the plant immune system as well as understanding the concept of the plant–pathogen–environment disease triangle and the emergence of new disease epidemics in a warming climate."
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