Transcription factor ScWRKY4 in sugarcane negatively regulates the resistance to pathogen infection through the JA signaling pathway

Abstract

WRKY transcription factor, the transcriptional regulators unique to plants, plays an important role in plant defense response to pathogen infection. However, the disease resistance mechanism of WRKY gene in sugarcane remains unclear. Previously, we identified a ScWRKY4 gene, a member of class IIc of the WRKY gene family, from the sugarcane cultivar ROC22. This gene could be induced by the stresses of salicylic acid (SA) and methyl jasmonate (MeJA). Interestingly, the expression of the ScWRKY4 gene was down-regulated in smut-resistant sugarcane cultivars but up-regulated in smut-susceptible sugarcane cultivars under Sporisorium scitamineum stress. Besides, stable overexpression of the ScWRKY4 gene in Nicotiana benthamiana enhanced susceptibility to Fusarium solani var. coeruleum and caused the down-regulated expression of immune marker-related genes. Furthermore, transcriptome analysis indicated that, the expression of most JAZ genes was suppressed in plant signal transduction pathway. In addition, ScWRKY4 could interact with ScJAZ13 and repress the expression of ScJAZ13. We thus hypothesized that the ScWRKY4 gene was involved in the regulatory network of plant disease resistance, most probably through the JA signaling pathway. The present study depicted the molecular mechanism of the ScWRKY4 gene involved in sugarcane disease resistance and laid the foundation for the subsequent investigation.