ZmMYC7 directly regulates ZmERF147 to increase maize resistance to Fusarium graminearum

Abstract

The jasmonic acid (JA) signaling pathway is involved in plant growth, development, and response to abiotic or biotic stresses. MYC2, a bHLH transcription factor, is a regulatory hub in the pathway. The function of ZmMYC7, a putative MYC2 ortholog, in jasmonate-signaled defense responses of maize has not been reported. In this study, we found that ZmMYC7 possesses JID, TAD, bHLH and Zip domains and essential characteristics of transcription factors: a nuclear location and transactivation activity. The ZmMYC7 mutants showed markedly increased sensitivity to Fusarium graminearum and Setosphaeria turcica. The expression levels of the defense-associated genes ZmPR1, ZmPR2, ZmPR3, ZmPR5, ZmPR6, and ZmPR7 in response to F. graminearum infection were downregulated in ZmMYC7 mutants, while ZmPR4 and ZmPR10 were up-regulated. ZmMYC7 interacted with members of the ZmJAZ family, including ZmJAZ8, ZmJAZ11, and ZmJAZ12. ZmMYC7 physically interacted with G-box cis-elements in the ZmERF147 promoter in vitro and transcriptional activation of ZmERF147 by ZmMYC7 was inhibited by ZmJAZ11 and ZmJAZ12. ZmERF147 mutants were more susceptible to F. graminearum infection than inbred line B73 with concomitant down-regulation of all defense-associated ZmPRs except ZmPR4. These findings indicate that ZmMYC7 functions in maize resistance to F. graminearum and sheds light on maize defense responses to pathogenic fungi via the JA signaling pathway.