Myo-
inositol participates in many different aspects of plant physiology and myo-
inositol 1-phosphate synthase (MIPS; EC 5.5.1.4) catalyzes the rate limiting step of
inositol biosynthetic pathway. Chickpea (Cicer arietinum), a drought-tolerant leguminous crop plant, is known to accumulate increased
inositol during
dehydration stress. Previously, we reported two differentially expressed divergent genes (CaMIPS1 and CaMIPS2) encoding two MIPS
isoforms in chickpea. In this communication, we demonstrated that CaMIPS2 is an early
dehydration-responsive gene and is also rapidly induced by exogenous ABA application, while CaMIPS1 expression is not much influenced by
dehydration or ABA. The regulation of expression of these two genes has been studied by examining their promoter activity through GUS reporter gene and differential promoter activity has been observed. Moreover, unlike CaMIPS1 promoter, CaMIPS2 promoter contains CRT/DRE cis-regulatory
element which seems to play a key role in
dehydration-induced expression of CaMIPS2. Furthermore, CaMIPS1 and CaMIPS2 have been successfully complemented and shown to repair the defect of seedling growth and altered seed phenotype of Atmips1 mutant. Moreover, Arabidopsis transgenic plants overexpressing CaMIPS1 or CaMIPS2 exhibit improved tolerance to salinity and
dehydration stresses and such tolerance of transgenic plants is correlated with their elevated level of
inositol. Remarkably, CaMIPS2 transgenic lines perform better in all attributes than CaMIPS1 transformants under such stress conditions, due to comparatively unabated production of
inositol by CaMIPS2
enzyme, as this
enzyme retains significant activity under stress conditions.