Comparative Functional Genomics Studies, Mapping And Cloning Of Genes Controlling Low Phytic Acid In Barley

Phytic acid (PA, myo-inositol 1,2,3,4,5,6-hexakisphosphate) is the primary storage form of phosphorus (P) in cereal seeds, accounting for about 65-85% the total P. It is is considered to be an anti-nutritional substance in animal feed and human diets, since it has the potential to form very stable complexes with minerals and proteins, which are poorly utilized to monogastric animals due to the absence or insufficient amount of the phytate degrading enzymes in their digestive system. As a result, it contributes to human mineral deficiency, especially in populations throughout the developing world that rely on grains and legumes as staple foods. In addition, it also contributes to the eutrophication of lakes and rivers, since large amounts of phytate-P are excreted to the environment with the animal waste. The development of plant cultivars with low phytic acid content is therefore an important priority.In the current study, we identified putative barley low phytic acid genes via comparative genomics analysis with rice, developed and mapped a set of functional gene markers to previously mapping results, using other crops lpa gene information and their homologous barley ESTs, cloned and alasysed one of the candidate gene by the method of in silico cloning combination with PCR amplification. The major results are as follows:1. The barley lpa1-1 mutation was localized to chromosome 2H. BLASTN analysis showed that nine markers at the 2H terminal region controlling low phytic acid were aligned to the rice genome sequences along the terminal region of rice chromosome 4. The candidate gene for lpa1-1 may be either the sulfate transporter (OsSultr3; 3) or inositol 1.4.5-trisphosphate 3-/6-kinase (OsIPK1) based on the barley and rice comparison. The lpa2-1 is located on barley chromosome 7H. Comparative mapping showed the relevant region of barley was collinear with a region on rice chromosome 6. The multidrug resistance associated protein gene (OsMRP11, OsMRP12 and OsMRP15) and sulfate transporter (OsSultr3; 4) may be the candidate gene for lpa2-1. The lpa3-1 and "M955" are situated on chromosome 1H. Comparative mapping showed the relevant region of barley was collinear with a Phylogenetic relationships among the plant sulfate transporters indicate that the predicted protein of HvST gene from barley and OsSultr3; 3 from rice fall into the group 3 of sulphate transporter gene family.