Closely-Spaced Repetitions of CAMTA Trans-Factor Binding Sites in Promoters of Model Plant MEP Pathway Genes

Abstract

Previous research has demonstrated the presence of two closely spaced repetitions of the rapid stress-responsive cis-active element RSRE (G/A/C)CGCG(C/G/T) in the 5′UTR of S. miltiorrhiza2C-methyl-D-erithrytol 2,4-cyclodiphosphate synthase (MECPS) gene. The product of MECPS activity, represented by 2C-methyl-D-erithrytol 2,4-cyclodiphosphate (MECPD), indicates its retrograde regulatory role and activates CAMTA trans-factors. Since the complete activation of CAMTA trans-factors requires the cooperative interaction of CAMTA3 with CAMTA2 or CAMTA4, the closely spaced RSREs recognized by CAMTA trans-factors could be used to promote CAMTA trans-factor dimerization. The present study aims to evaluate if the occurrence of these two closely spaced RSREs in the 5′UTR is specific to S. miltiorrhiza or could be observed in other MECPS genes. An analysis of nineteen MECPS gene sequences from seven selected model plants indicated the closely spaced repetition of RSREs in the 5′UTR region of two maize (Zea mays) MECPS genes, Zm00001d051458 and Zm00001d017608. This observation suggests the potential autoregulatory function of MECPD in relation to the MECPS transcription rate. Moreover, an analysis of eighty-five promoter regions of other plastidial methyl-D-erythritol phosphate (MEP) pathway genes indicated such closely spaced RSREs in the proximal promoter of Zea mays2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (CMS) (Zm00001d012197) and Oryza sativa4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR) (Os03t0732000-00).