Genetic and molecular characterization of the low phytic acid (Lpa1) locus in rice (Oryza sativa L.)

The rice low phytic acid (lpa1) mutant has a 45% reduction in seed phytic acid and a molar equivalent increase in inorganic P. The rice lpa1 mutation was mapped to rice chromosome 2L. This research aims to identify the rice Lpa1 gene using a positional cloning and candidate gene approach, characterize the rice Lpa1 gene expression and identify lpa1 mutant alleles for functional analysis. High resolution genetic mapping of the rice lpa1 mutation resulted in the identification of an 8 kb region on chromosome 2 containing a single candidate gene (LOC_Os02g57400) with homology to 2-phosphoglycerate kinase. Sequence analysis of the candidate gene from the two independent mutants (KB1-1 and DR1331-2) confirmed that (LOC_Os02g57400) is the rice Lpa1 gene (OsLpa1). This gene has three alternative splice variants which have been confirmed by expression analysis. The location and nature of the two mutations suggests that the lesion affect the translation of the predicted protein derived from the longest transcript. OsLpa1 represents a novel gene involved in phytic acid metabolism. The identification of Lpa1 gene as well as generation of additional mutants for future study will contribute to the understanding of the phytic acid biosynthesis and accumulation in plants.