A defective ABC transporter of the MRP family, responsible for the bean lpa1 mutation, affects the regulation of the phytic acid pathway, reduces seed myo-inositol and alters ABA sensitivity

• We previously identified the lpa1 (low phytic acid) 280-10 line that carries amutation conferring a 90% reduction in phytic acid (InsP6) content. In contrast toother lpa mutants, lpa1(280-10) does not display negative pleiotropic effects. Inthe present paper, we have identified the mutated gene and analysed its impact onthe phytic acid pathway.• Here, we mapped the lpa1(280-10) mutation by bulk analysis on a segregatingF2 population, an then, by comparison with the soybean genome, we identifiedand sequenced a candidate gene. The InsP6 pathway was analysed by geneexpression and quantification of metabolites.• The mutated Pvmrp1(280-10) cosegregates with the lpa1(280-10) mutation,and the expression level of several genes of the InsP6 pathway are reduced in thelpa1(280-10) mutant as well as the inositol and raffinosaccharide content.PvMrp2, a very similar paralogue of PvMrp1 was also mapped and sequenced.• The lpa1 mutation in beans is likely the result of a defective Mrp1 gene (orthologousto the lpa genes AtMRP5 and ZmMRP4), while its Mrp2 paralog is not ableto complement the mutant phenotype in the seed. This mutation appears todown-regulate the InsP6 pathway at the transcriptional level, as well as alteringinositol-related metabolism and affecting ABA sensitivity.