Abstract
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.
Highlights
Gene expression is largely controlled through promoters and their contributing cis-acting elements that are positioned upstream of the transcriptional start site of a gene
In order to elucidate the mechanism of transcriptional regulation of wheat Phytic acid (PA) pathway genes, analysis of their promoter region was performed for the cis-elements
TaIMP was not included in promoter analysis due to its inadequate information in the International Wheat Genome Sequencing Consortium (IWGSC)
Summary
Gene expression is largely controlled through promoters and their contributing cis-acting elements that are positioned upstream of the transcriptional start site of a gene. The Inositol pentakisphosphate kinase (IPK1) is involved in the final step in phytic acid biosynthesis. This step is common to both lipid-dependent and independent pathways. In order to understand the regulation of PA pathway genes, especially in seeds, the effect of hormones was studied previously in rice [14]. It has been shown that the wheat MIPS gene, which is involved in earlier steps of PA biosynthesis, is inducible by ABA, salicylic acid (SA) and other abiotic stresses [35]. It would be interesting to study the temporal expression of genes involved in phytic acid biosynthesis under exogenous application of hormones (ABA or GA3) and biochemicals (SA or cAMP). Our results suggested a coordinated and time-dependent response of the phytic acid biosynthetic genes when exogenously exposed to these hormones and signaling molecules
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