The Arabidopsis JAZ2 Promoter Contains a G-Box and Thymidine-Rich Module that are Necessary and Sufficient for Jasmonate-Dependent Activation by MYC Transcription Factors and Repression by JAZ Proteins

Abstract

Jasmonate (JA) is a critical hormone for both plant defense and reproductive development. Until now, early JA-responsive promoters have not been well characterized. To identify the cis-acting DNA element involved in the early JA response at the transcriptional level, we analyzed the promoter of the Arabidopsis gene encoding jasmonate-ZIM domain2 protein (JAZ2). The full-length JAZ2 promoter in JAZ2::GUS plants is active in vegetative and reproductive tissue, with expression in stamen filaments being dependent on JA biosynthesis. We identified a G-box element in the JAZ2 promoter that is required for JA-mediated promoter activation in carrot protoplasts and Arabidopsis seedlings. Three copies of a G-box and flanking sequences has autonomous JA-dependent activity and was transactivated by MYC2, MYC3 and MYC4 transcription factors in carrot protoplasts. Expression of MYC2, MYC3 or MYC4 fused to an EAR (ETHYLENE RESPONSE FACTOR-associated amphiphilic repression) motif, or expression of JAZ1 or JAZ6 all repressed JA- and MYC-dependent activation of the JAZ2 promoter. A thymidine-rich sequence 3' to the G-box was required for full JA activation of the JAZ2 promoter. Because the G-box is also present in genes unresponsive to JA, we propose that this thymidine-rich sequence together with the G-box provides JA specificity to promoters induced early in the JA response. Together, these results indicate that an extended G-box located in the promoter region of an early JA-responsive gene is required for gene induction in vivo, probably through selective binding of MYC2, MYC3 and MYC4 transcription factors.