L- Myo-Inositol 1-Phosphate Synthase (MIPS) in Chickpea: Gene Duplication and Functional Divergence

Gene duplication is one of the key driving forces in the evolution of genes and important features of genomic architecture of living organisms including plants. Moreover, much of the plant diversity may have arisen largely due to duplication, followed by divergence and adaptive specialization of the pre existing genes (Ohno,1970; Zhang, 2003; Flagel & Wendel,2009). Current impetus on genomic sequence data provides substantial evidence for the profusion of duplicated genes in all organisms surveyed. Functional divergence after gene duplication can possibly result in two alternative evolutionary fates: i) neofunctionalization where one copy acquires an entirely new function whereas the other copy maintains the original function. ii) Subfunctionalization, in which each copy adopts part of the task of their parental gene (Ohno,1970; Nowak et al., 1997; Jenesen,1976; Orgel,1977;Hughes,1994). However, subfunctionalization is reported as a more prevalent outcome than neofunctionalization in nature. In any case, functional divergence of such paralogous proteins is found to be the key force shaping molecular network in organisms (Ohno, 1970). Recent studies also suggest that duplicate genes diverge mostly through the partitioning of gene expression as in subfunctionalization (Force et al.,1999; Wagner,2000; Gu et al.,2002). In addition, subfunctionalization can also take place at the protein function level leading to functional specialization, when one of the duplicated genes becomes better at performing one of the original functions of the progenitor gene (Hughes, 1994; Gu et al.,2002; Conant W Hughes, 1999; Zhang et al., 2002). Myo-inositol-1-phosphate synthase (MIPS;EC5.5.1.4) is an evolutionary conserved enzyme which catalyzes the rate limiting step in well conserved inositol biosynthetic pathway and is extremely widespread in living organisms including plants (Loewus & Murthy, 2000; Majumder et al., 2003). The evolution of MIPS gene/ protein among the prokaryotes seems to be more divergent and complex than amongst the eukaryotes, however they preserve a conserve core catalytic domain among the MIPS proteins (Majumder et al., 2003). Many of the plant species are known to contain more than one copy of gene encoding MIPS and are hypothesized to arise through gene duplication. Expression studies of multiple gene encoding MIPS have revealed the possibility of specialized role for individual enzyme isoforms. Previously, two genes encoding MIPS have been identified and characterized from chickpea by Kaur et al. A comparative study of two divergent genes (CaMIPS1 & CaMIPS2)