title: Silencing of tomato RBOH1 and MPK2 abolishes brassinosteroid-induced H₂O₂ generation and stress tolerance.
abstract: Brassinosteroids (BRs) are involved in the regulation of plant growth, development and stress responses. While the signalling pathways for BR-regulated plant growth and development are well studied, the mechanisms by which BRs regulate plant stress tolerance remain largely unclear. Here we showed that 24-epibrassinolide (EBR), which induced tolerance to oxidative and heat stress in tomato, was also capable of elevating the transcript levels of RBOH1, MPK1 and MPK2, increasing apoplastic H2 O2 accumulation, and enhancing activation of MPK1/2. Virus-induced gene silencing of RBOH1, MPK1, MPK2 and MPK1/2 resulted in reduced stress tolerance. Silencing of RBOH1 had no effect on the transcripts of MPK1 and MPK2 but inhibited MPK1/2 activation and H2 O2 accumulation. Silencing of either MPK1 or MPK2, on the other hand, reduced RBOH1 transcript, H2 O2 accumulation and MPK1/2 activity. BR-induced tolerance and MPK1/2 activation were compromised in RBOH1-, MPK2- and MPK1/2-silenced plants but not in MPK1-silenced plants. These results suggested that MPK2 played a more critical role than MPK1 in EBR-induced apoplastic H2 O2 accumulation. RBOH1, MPK1 and MPK2 were involved in the stress tolerance and BR-induced stress tolerance likely involved a positive feedback loop among RBOH1, H2 O2 and MPK2, leading to sustained apoplastic accumulation of H2 O2 and related signalling processes.
authors.affiliation: Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China.
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Nie
authors.forename: Meng-Meng
authors.initials: MM
authors.lastname: Wang
authors.forename: Xiao-Jian
authors.initials: XJ
authors.lastname: Xia
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Zhou
authors.forename: Kai
authors.initials: K
authors.lastname: Shi
authors.forename: Zhixiang
authors.initials: Z
authors.lastname: Chen
authors.forename: Jing Quan
authors.initials: JQ
authors.lastname: Yu
mesh_terms: D000222:Adaptation, Physiological; D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis; D060406:Brassinosteroids / Q000494:pharmacology*; D002245:Carbon Dioxide / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D006358:Hot Temperature; D006861:Hydrogen Peroxide / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000975:Antioxidants; D060406:Brassinosteroids; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D017382:Reactive Oxygen Species; D013260:Steroids, Heterocyclic; D002245:Carbon Dioxide; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; C023623:brassinolide