Isolation and characterization of a new low phytic acid mutant in the common bean PvMRP1 gene and study of PvMRPs promoters in two different plant systems

Phytic acid (InsP6) is the main storage form for phosphate in seeds and in the plant it plays an important role in signal transduction in response to environmental stress and hormonal changes. InsP6 is a strong chelator of mono and divalent cations, such as iron, zinc, magnesium and calcium, essential minerals in the diet, reducing their bioavailabilty. We previously isolated the common bean lpa1-1 mutant, affected in the PvMRP1 gene, coding for a putative tonoplastic phytic acid transporter. With the aim to isolate new common bean lpa mutants we partially screened an EMS population and identified a new lpa mutant, hereinafter called lpa1-2, as it resulted allelic to lpa1-1 mutant. The lpa1-2 mutation consists in a premature stop codon. In this work, we present preliminary data of the phenotypic characterization of lpa1-2 mutant. In common bean there is also the PvMRP2 gene, paralog of PvMRP1, probably able to complement the lpa1 phenotype in other tissues than the seed, thus explaining the lack of pleiotropic effects in the bean mutant. In order to analyze promoters of these two genes, constructs harboring portions of 1.5 kb of their putative sequences fused upstream of the GUS reporter were generated and used to transform two species: Arabidopsis thaliana and Medicago truncatula. Data on reporter expression in both plant systems will be presented.