ABSTRACT
Phosphate (Pi) and MYC2-mediated jasmonate (JA) pathway play critical roles in plant growth and development. In particular, crosstalk between JA and Pi starvation signalling has been reported to mediate insect herbivory resistance in dicot plants. However, its roles and mechanism in monocot-bacterial defense systems remain obscure. Here, we report that Pi starvation in rice activates the OsMYC2 signalling and enhances resistance to Xanthomonas oryzae pv. oryzae (Xoo) infection. The direct regulation of OsPHR2 on the OsMYC2 promoter was confirmed by yeast one-hybrid, electrophoretic mobility shift, dual-luciferase and chromatin immunoprecipitation assays. Molecular analyses and infection studies using OsPHR2-Ov1 and phr2 mutants further demonstrated that OsPHR2 enhances antibacterial resistance via transcriptional regulation of OsMYC2 expression, indicating a positive role of OsPHR2-OsMYC2 crosstalk in modulating the OsMYC2 signalling and Xoo infection. Genetic analysis and infection assays using myc2 mutants revealed that Pi starvation-induced OsMYC2 signalling activation and consequent Xoo resistance depends on the regulation of OsMYC2. Together, these results reveal a clear interlink between Pi starvation- and OsMYC2- signalling in monocot plants, and provide new insight into how plants balance growth and defence by integrating nutrient deficiency and phytohormone signalling. We highlighted a molecular link connecting OsMYC2-mediated JA pathway and phosphate starvation signalling in monocot plant. We demonstrated that phosphate starvation promoted OsMYC2 signalling to enhance rice defence to bacterial blight via transcriptional regulation of OsPHR2 on OsMYC2.
Subject(s)
Oryza/genetics , Phosphorus/deficiency , Plant Diseases/genetics , Plant Proteins/genetics , Xanthomonas/physiology , Cyclopentanes/metabolism , Disease Resistance/genetics , Oryza/metabolism , Oxylipins/metabolism , Plant Diseases/microbiology , Plant Proteins/metabolism , Signal Transduction/geneticsABSTRACT
MAIN CONCLUSION: Genome-wide identification, expression analysis of the MYC family in Camellia sinensis, and potential functional characterization of CsMYC2.1 have laid a solid foundation for further research on CsMYC2.1 in jasmonate (JA)-mediated response. Myelocytomatosis (MYC) of basic helix-loop-helix (bHLH) plays a major role in JA-mediated plant growth and developmental processes through specifically binding to the G-box in the promoters of their target genes. In Camellia sinensis, studies on the MYC gene family are limited. Here, we identified 14 C. sinensis MYC (CsMYC) genes, and further analyzed the evolutionary relationship, gene structure, and motif pattern among them. The expression patterns of these CsMYC genes in different tissues suggested their important roles in diverse function in tea plant. Four MYC transcription factors with the highest homology to MYC2 in Arabidopsis were localized in the nucleus. Two of them, named CsMYC2.1 and CsMYC2.2, exhibited transcriptional self-activating activity, and, therefore, could significantly activate the promoter containing G-box motif, whereas CsJAM1.1 and CsJAM1.2 lack the transcriptional self-activating activity, indirectly mediating the JA pathway through interacting with CsMYC2.1 and CsMYC2.2. Furthermore, Yeast Two-Hybrid (Y2H) and Bimolecular Fluorescent Complimentary (BiFC) assays showed that CsMYC2.1 could interact with CsJAZ3/7/8 proteins. Genetically, the complementation of CsMYC2.1 in myc2 mutants conferred the ability to restore the sensitivity to JA signals. The results provide a comprehensive characterization of the 14 CsMYCs in C. sinensis, establishing a solid foundation for further research on CsMYCs in JA-mediated response.
