Abstract
Most of the phosphorus in seeds is accumulated in the form of phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6). This molecule is a strong chelator of cations important for nutrition, such as iron, zinc, magnesium, and calcium. For this reason, InsP6 is considered an antinutritional factor. In recent years, efforts to biofortify seeds through the generation of low phytic acid (lpa) mutants have been noteworthy. Moreover, genes involved in the biosynthesis and accumulation of this molecule have been isolated and characterized in different species. Beyond its role in phosphorus storage, phytic acid is a very important signaling molecule involved in different regulatory processes during plant development and responses to different stimuli. Consequently, many lpa mutants show different negative pleitotropic effects. The strength of these pleiotropic effects depends on the specific mutated gene, possible functional redundancy, the nature of the mutation, and the spatio-temporal expression of the gene. Breeding programs or transgenic approaches aimed at development of new lpa mutants must take into consideration these different aspects in order to maximize the utility of these mutants.
Highlights
Phytic acid is a ubiquitous component of eukaryotic cells which, together with its metabolism, plays a number of regulatory roles [1]
Phytic acid is stored as globoids inside the storage vacuoles where it is actively transported by a specific InsP6 transporter, a multidrug-resistance-associated protein (MRP), belonging to the ATP-binding cassette (ABC) family [27]
Genes involved in phytic acid biosynthesis and transport have been characterized in Arabidopsis thaliana and crop plants such as rice, wheat, soybean and common bean, through forward and reverse genetics [35,36,37,38,39]
Summary
Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, InsP6) is a ubiquitous component of eukaryotic cells which, together with its metabolism, plays a number of regulatory roles [1]. A common practice to provide for an animal’s nutritional requirement for phosphorus (P) has been the supplementation of feed with nutrient P This procedure increases P concentration in manure, leading to P accumulation in soils, and the consequent risk of P pollution in runoff water [13]. To obviate these problems, a solution is the development of low phytic acid (lpa) crop seeds [14]. Reducing seed total P, together with a reduction of phytate content, might contribute to these goals [17] This has been achieved at least for the barley lpa mutant, in which seeds show a decrease both in phytic acid and total P [18]. We discuss some pleiotropic effects of lpa mutants with respect to the reported roles, important for cell signaling and plant processes, of phytic acid and key enzymes and metabolites of this complex pathway
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