Characterization of the MIPS gene family in Glycine max

Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate) is the primary storage component of phosphorus in plant seeds. The first step in phytic acid biosynthesis is the de novo synthesis of myo-inositol, which is catalyzed by the enzyme D-myo-inositol 3-phosphate synthase (MIPS EC 5.5.1.4). Previous work detected four MIPS genes in soybean (Glycine max). However, only a limited amount of data were available for the MIPS gene family and some of the data were conflicting. The work described here clears up these data and characterizes the MIPS gene family for the purposes of reverse genetic technologies. The complete genomic sequence of all four genes was determined and their expression profile was examined by quantitative real-time reverse transcription-polymerase chain reaction. Our results indicate that the four MIPS genes are highly conserved and temporally and spatially expressed. The MIPS gene family in the low phytic acid soybean line, CX1834, was also characterized since this line displays a phenotype similar to previously characterized MIPS mutants. These data demonstrate that mutations in MIPS genes are not the cause of the low phytic acid phenotype.