Phytic acid (myo-inositol-hexa-kis-phosphate, InsP6) is the main storage form for phosphate in plant seeds. From nutritional point of view it decreases the seed value by chelating important minerals, such as iron, zinc, magnesium, and calcium. Therefore, the isolation of low phytic acid (lpa) mutants is considered a highly desirable objective in the genetic improvement of the nutritional quality of grain crops. On the other side phytic acid is a very important signaling molecule, involved in development and hormonal regulation. For this reason lpa mutants are often associated with negative pleiotropic effects such as compromised germination and emergence, lower stress tolerance and poor seed filling. The only phytic acid transporters, characterized so far, are proteins of the ABCC type. Some lpa mutants affected in these transporters have been isolated and characterized in different species, including the Phaseolus vulgaris lpa-1 mutant, affected in the PvMRP1 (PvABBC1) gene. Failure of InsP6 transport in lpa mutants causes perturbations of inositol and inositol phosphate metabolism, thus the pleiotropic effects reflect the relevance of InsP6, inositol phosphates and their key precursor, myo-inositol, in fundamental signaling and developmental pathways. At the molecular level the most stricking feature shared by lpa mutants affected in genes coding for MRP type ABC InsP6 transporters is the reduced expression of MIPS, and, where reported, of genes coding for other enzymes involved in InsP6 biosynthesis (IPK1, IPK2, ITPK, IMP, MIK). Aim of this work is to have a more detailed picture on the effects of this kind of mutation on the spatial and temporal expression of the InP6 genes during seed development. For this purpose in situ hybridization analysis of PvMIPSs, PvIMP, PvIPK1 and PvIPK2 genes during common bean seed development in wild type and lpa-1 genotypes is in progress. Moreover the same kind of analysis was performed on the PvMRP1gene transcript and also on PvMRP2, a paralog of PvMRP1. The main result from this detailed expression analyses revealed a reduction of transcript accumulation in specific seed compartments in the lpa-1 genotype for different genes involved in InsP6 synthesis and transport, instead of a general reduction in the entire seed area. This analysis will help in elucidating the complex interaction between different seed compartments occurring during the synthesis and subsequent accumulation of InsP6 in developing seeds of common bean. This work was supported by the Programme FILAGRO "Strategie innovative e sostenibili per la filiera agroalimentare", as part of the activities defined within the Accordo Quadro Consiglio Nazionale delle Ricerche and Regione Lombardia
THE low phytic acid-1 MUTATION IN P. vulgaris: EFFECTS ON THE TEMPORAL AND SPATIAL EXPRESSION OF GENES INVOLVED IN PHYTIC ACID SYNTHESIS AND TRANSPORT
PAOLO D;COMINELLI E;DAMINATI M G;BOLLINI R;SPARVOLI F
2015
Abstract
Phytic acid (myo-inositol-hexa-kis-phosphate, InsP6) is the main storage form for phosphate in plant seeds. From nutritional point of view it decreases the seed value by chelating important minerals, such as iron, zinc, magnesium, and calcium. Therefore, the isolation of low phytic acid (lpa) mutants is considered a highly desirable objective in the genetic improvement of the nutritional quality of grain crops. On the other side phytic acid is a very important signaling molecule, involved in development and hormonal regulation. For this reason lpa mutants are often associated with negative pleiotropic effects such as compromised germination and emergence, lower stress tolerance and poor seed filling. The only phytic acid transporters, characterized so far, are proteins of the ABCC type. Some lpa mutants affected in these transporters have been isolated and characterized in different species, including the Phaseolus vulgaris lpa-1 mutant, affected in the PvMRP1 (PvABBC1) gene. Failure of InsP6 transport in lpa mutants causes perturbations of inositol and inositol phosphate metabolism, thus the pleiotropic effects reflect the relevance of InsP6, inositol phosphates and their key precursor, myo-inositol, in fundamental signaling and developmental pathways. At the molecular level the most stricking feature shared by lpa mutants affected in genes coding for MRP type ABC InsP6 transporters is the reduced expression of MIPS, and, where reported, of genes coding for other enzymes involved in InsP6 biosynthesis (IPK1, IPK2, ITPK, IMP, MIK). Aim of this work is to have a more detailed picture on the effects of this kind of mutation on the spatial and temporal expression of the InP6 genes during seed development. For this purpose in situ hybridization analysis of PvMIPSs, PvIMP, PvIPK1 and PvIPK2 genes during common bean seed development in wild type and lpa-1 genotypes is in progress. Moreover the same kind of analysis was performed on the PvMRP1gene transcript and also on PvMRP2, a paralog of PvMRP1. The main result from this detailed expression analyses revealed a reduction of transcript accumulation in specific seed compartments in the lpa-1 genotype for different genes involved in InsP6 synthesis and transport, instead of a general reduction in the entire seed area. This analysis will help in elucidating the complex interaction between different seed compartments occurring during the synthesis and subsequent accumulation of InsP6 in developing seeds of common bean. This work was supported by the Programme FILAGRO "Strategie innovative e sostenibili per la filiera agroalimentare", as part of the activities defined within the Accordo Quadro Consiglio Nazionale delle Ricerche and Regione LombardiaI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
