Regulation of OsPR10a Promoter Activity by Phytohormone and Pathogen Stimulation in Rice

Abstract OsPR10a is one of the well known pathogenesis-related genes in rice, and is induced by multiple plant hormones and pathogens. However, the underlying transcriptional regulation mechanisms in response to different signals and their crosstalks are still largely unknown. In order to find new players participated in the activation of OsPR10a, we systematically analyzed the basal expression patterns as well as the expression responses of a 2.5 kb OsPR10a promoter in rice transgenic plants after phytohormone and pathogen stimulations. In agreement with the native gene expression, the OsPR10a promoter can drive glucuronidase (GUS) gene expressing in spots of leaf cells, leaf trichomes, lemmas and paleae, germinating embryos, calli and root tips. The leaf expression of OsPR10a::GUS was dramatically increased upon jasmonic acid (JA) and cytokinin (CK) treatments, or challenges of the pathogen Magnaporthe grisea and Xanthomonas oryzae pv. oryzae. Thus, the OsPR10a promoter reported here can faithfully reflect its native gene expression. The effects of several JA and CK responsive OsWRKY genes on the regulation of OsPR10a promoter were then inspected by luciferase transient expression assay, and the JA inducible OsWRKY10 transcription factor was found as a new positive regulator of OsPR10a. However, the key transcription factors of JA and CK signaling pathways, OsMYC2 and B-type response regulators, were not responsible for the activation of OsPR10a promoter. Our findings provided new insights into the regulation of OsPR10a expression during plant-hormone/pathogen interactions, and the OsPR10a reporter system can be useful to unravel novel regulators from both pathogen and host.