Journal
PLANT CELL AND ENVIRONMENT
Volume 36, Issue 4, Pages 789-803Publisher
WILEY
DOI: 10.1111/pce.12014
Keywords
brassinosteroids; defence response; hydrogen peroxide; mitogen-activated protein kinase; photooxidation; reactive oxygen species; signal transduction
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Funding
- National Basic Research Program of China [2009CB119000]
- National Natural Science Foundation of China [31071790, 30972033]
- National Key Technology R & D program of China [2011BAD12B04]
- Program for New Century Excellent Talents in University
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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 H2O2 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 H2O2 accumulation. Silencing of either MPK1 or MPK2, on the other hand, reduced RBOH1 transcript, H2O2 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 H2O2 accumulation. RBOH1, MPK1 and MPK2 were involved in the stress tolerance and BR-induced stress tolerance likely involved a positive feedback loop among RBOH1, H2O2 and MPK2, leading to sustained apoplastic accumulation of H2O2 and related signalling processes.
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