Phytic acid (PA) biosynthesis pathway genes were reported from multiple crop species. PA accumulation was enhanced during grain filling and at that time, hormones like Abscisic acid (ABA) and Gibberellic acid (GA₃) interplay to control the process of seed development. Regulation of wheat PA pathway genes has not yet been reported in seeds. In an attempt to find the clues for the regulation by hormones, the promoter region of wheat PA pathway genes was analyzed for the presence of cis-elements. Multiple cis-elements of those known to be involved for ABA, GA₃, salicylic acid (SA), and cAMP sensing were identified in the promoters of PA pathway genes. Eight genes (TaIMP, TaITPK1-4, TaPLC1, TaIPK2 and TaIPK1) involved in the wheat PA biosynthesis pathway were selected for the expression studies. The temporal expression response was studied in seeds treated with ABA and GA₃ using quantitative real time PCR. Our results suggested that exogenous application of ABA induces few PA pathway genes in wheat grains. Comparison of expression profiles for PA pathway for GA₃ and ABA suggested the antagonistic regulation of certain genes. Additionally, to reveal stress responses of wheat PA pathway genes, expression was also studied in the presence of SA and cAMP. Results suggested SA specific differential expression of few genes, whereas, overall repression of genes was observed in cAMP treated samples. This study is an effort to understand the regulation of PA biosynthesis genes in wheat.

Low phytic acid is a trait desired in cereal crops and can be achieved by manipulating the genes involved either in its biosynthesis or its transport in the vacuoles. Previously, we have demonstrated that the wheat TaABCC13 protein is a functional transporter, primarily involved in heavy metal tolerance, and a probable candidate gene to achieve low phytate wheat. In the current study, RNA silencing was used to knockdown the expression of TaABCC13 in order to evaluate its functional importance in wheat. Transgenic plants with significantly reduced TaABCC13 transcripts in either seeds or roots were selected for further studies. Homozygous RNAi lines K1B4 and K4G7 exhibited 34-22% reduction of the phytic acid content in the mature grains (T4 seeds). These transgenic lines were defective for spike development, as characterized by reduced grain filling and numbers of spikelets. The seeds of transgenic wheat had delayed germination, but the viability of the seedlings was unaffected. Interestingly, early emergence of lateral roots was observed in TaABCC13-silenced lines as compared to non-transgenic lines. In addition, these lines also had defects in metal uptake and development of lateral roots in the presence of cadmium stress. Our results suggest roles of TaABCC13 in lateral root initiation and enhanced sensitivity towards heavy metals. Taken together, these data demonstrate that wheat ABCC13 is functionally important for grain development and plays an important role during detoxification of heavy metals.