Comparative Expression and Cellular Localization of Myo-inositol Phosphate Synthase (MIPS) in the Wild Type and in an EMS Mutant During Common Bean (Phaseolus vulgaris L.) Seed Development

In plants, the myo-inositol-1-phosphate synthase (EC 5.5.1.4; MIPS) is an evolutionarily conserved enzyme protein and catalyzes the synthesis of myo-inositol, which is a central molecule required for cell metabolism and plant growth. A full-length cDNA encoding common bean (Phaseolus vulgaris L.) MIPS (designated Pv_BAT93 MIPS) was isolated from seed of P. vulgaris (cv, BAT93) by rapid amplification of cDNA ends. The cDNA of Pv_BAT93 MIPS comprised 1,873 bp, which encodes 510 amino acids. The Pv_BAT93 MIPS gene was highly homologous with those of other plant species, such as P. vulgaris (cv, Taylor's Horticultural), Arabidopsis thaliana, Medicago sativa and Glycine max. DNA blot analysis indicated that at least three copies of MIPS are present in the common bean genome. RT-PCR analysis indicated that the Pv_BAT93 MIPS transcripts existed in developing seeds and other common bean tissues, including leaves, flowers, and cotyledons but showed lower levels expression in roots and stems. Real-time quantitative PCR showed that Pv_BAT93 MIPS gene is differentially expressed during common bean seed development. In situ hybridization of developing seeds in the wild type and in the ethyl methanesulfonate mutant showed that expression of Pv_BAT93 MIPS was identified in the embryo tissues, from the globular to late cotyledon stages, confirming a possible involvement of Pv_BAT93 MIPS in common bean seed development.