Overexpression ofOsMYC2Results in the Up-Regulation of Early JA-Rresponsive Genes and Bacterial Blight Resistance in Rice

Abstract

JASMONATE ZIM-domain (JAZ) proteins act as transcriptional repressors of jasmonic acid (JA) responses and play a crucial role in the regulation of host immunity in plants. Here, we report that OsMYC2, a JAZ-interacting transcription factor in rice (Oryza sativa L.), plays an important role in the resistance response against rice bacterial blight, which is one of the most serious diseases in rice, caused by Xanthomonas oryzae pv. oryzae (Xoo). The results showed that OsMYC2 interacted with some OsJAZ proteins in a JAZ-interacting domain (JID)-dependent manner. The up-regulation of OsMYC2 in response to JA was regulated by OsJAZ8. Transgenic rice plants overexpressing OsMYC2 exhibited a JA-hypersensitive phenotype and were more resistant to Xoo. A large-scale microarray analysis revealed that OsMYC2 up-regulated OsJAZ10 as well as many other defense-related genes. OsMYC2 selectively bound to the G-box-like motif of the OsJAZ10 promoter in vivo and regulated the expression of early JA-responsive genes, but not of late JA-responsive genes. The nuclear localization of OsMYC2 depended on a nuclear localization signal within JID. Overall, we conclude that OsMYC2 acts as a positive regulator of early JA signals in the JA-induced resistance against Xoo in rice.

OsMYC2, an essential factor for JA-inductive sakuranetin production in rice, interacts with MYC2-like proteins that enhance its transactivation ability

“…In rice, OsMYC2 has also been shown to be involved in JA-signalling through interaction with JAZ repressor proteins23. The luciferase activity assay clearly demonstrated that OsMYC2 has a positive impact on the expression of OsNOMT .…”

“…As a result, various types of 41 TFs comprising bHLH, MYB, NAC, WRKY, and bZIP families were selected (see Supplementary Table S2), and they included the JA-inductive bHLH factor OsMYC2 and MYB factor OsJAmyb. The expression of OsMYC2 is induced by JA treatment23. Several MYB proteins activate flavonoid biosynthetic genes by interacting with bHLH TFs24.…”

“…Uji et al . reported that OsMYC2 binds to a specific E-box sequence of the OsJAZ10 promoter in vivo by using the chromatin immunoprecipitation strategy23. Therefore, in vivo experimental approaches would be required to understand OsMYC2 binding on the OsNOMT promoter.…”

“…Another study revealed that OsMYC2 interacts with almost all of 14 JASMONATE ZIM-domain (JAZ) proteins in rice via the JAZ-interacting domain, one of which represses JA-inducible OsMYC2 expression. Furthermore, overexpression of OsMYC2 causes upregulation of early JA-responsive genes, leading to JA-hypersensitive phenotypes such as bacterial blight resistance23. However, the mechanism underlying the activation of the downstream pathway of OsMYC2 remains largely unknown.…”

Overexpression of a cell wall damage induced transcription factor, OsWRKY42, leads to enhanced callose deposition and tolerance to salt stress but does not enhance tolerance to bacterial infection

“…For example, treatment with MeJA inhibits root growth in Arabidopsis [34]. Rice plants overexpressing OsMYC2 , a JA response gene, exhibited a dwarf phenotype [35]. Overexpression of allene oxide cyclase in Artemisia annua , had a negative effect on plant growth [36].…”