Abstract
Jasmonic acid (JA) is an important plant hormone involved in regulation of many aspects of plant growth and development including secondary metabolism and JASMONATE ZIM-DOMAIN (JAZ) proteins are key components in JA signal processes. In this study, two new JAZ genes named SmJAZ3 and SmJAZ9 were cloned from S. miltiorrhiza hairy roots and characterized. Expression profiles under methyl jasmonate (MJ) treatment revealed that SmJAZ3 and SmJAZ9 were both MJ-responsive. Subcellular localization assay showed that SmJAZ3 was located in nucleus while SmJAZ9 was preferentially in nucleus. Expression of SmJAZ3 and SmJAZ9 in S. miltiorrhiza hairy roots differently affected the production of tanshinone. Over-expression of SmJAZ3 or SmJAZ9 in hairy roots produced lower level of tanshinone compared with the control, tanshinone production was as low as 0.077 mg/g DW in line SmJAZ3-3 and 0.266 mg/g DW in line SmJAZ9-22. Whereas, down-regulation of SmJAZs enhanced tanshione production, the content of tanshinone increased to 2.48 fold in anti-SmJAZ3-3 line, and 1.35-fold in anti-SmJAZ9-23 line. Our work indicated that SmJAZ3 and SmJAZ9 are involved in regulation of tanshinone biosynthesis and act as repressive transcriptional regulators in the JA signaling pathway, which paves the way to further dissect molecular mechanism in details in the future.
Highlights
Of JASMONATE Zinc-finger inflorescence meristem (ZIM)-DOMAIN (JAZ) repressors releases MYC2 transcription factor(s) through repression or activation the transcription of genes involved in plant defense responses[15,18]
Our results showed only SmJAZ9 can interact with AtMYC2 whereas SmJAZ3 couldn’t, which implied some degree of interaction of JASMONATE ZIM-DOMAIN (JAZ) and MYC2 possibly existed in S. miltiorrhiza to regulate biosynthesis
Two JAZ genes SmJAZ3 and SmJAZ9 were cloned from S. miltiorrhiza and functionally identified as repressors involved in tanshinone biosynthesis
Summary
Of JAZ repressors releases MYC2 transcription factor(s) through repression or activation the transcription of genes involved in plant defense responses[15,18]. JAZ family, interact with MYC2 transcription factor and repress its function in JA signaling, and act as repressors[17,19]. Enhanced accumulation of tanshinone elicited by addition of exogenous JA treatment in S. miltiorrhiza has been reported[28,29], but the exact molecular regulation mechanism are still unclear. As a key regulator in plant JA signal pathway reported recently, JAZ repression proteins should have important regulatory role in tanshinone biosynthesis in S. miltiorrhiza. Little is known about exact role of JAZ on tanshinone biosynthesis in S. miltiorrhiza. Two genes of JAZ family were isolated from S. miltiorrhiza and their roles in regulating the tanshinone biosynthetic pathway are functionally identified through genetic engineering strategy
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