Forward genetics studies of seed phytic acid

Abstract

Both the chemical composition and total amount of seed phosphorus (P) are important to the end-use quality of cereal and legume seed crops. The chemistry of seed total largely revolves around the synthesis and storage of phytic acid (myo-inositol hexaphosphate). Forward genetics research, beginning with the isolation of phytic acid (lpa) mutants, has led to the identification of genes important to phytic acid synthesis and transport in seeds. Lpa mutations have been isolated in maize (Zea mays L.), barley (Hordeum vulgare L.), rice (Oryza sativa L.), wheat (Triticum aestivum L.), and soybean (Glycine max L. (Merr.)), and chromosomal mapping has identified as many as six non-allelic loci in a single species (barley). These recessive alleles have been used to breed low-phytate cultivars, inbreds, and hybrids, and these have subsequently been used in biological, agronomic, and nutritional studies. One interesting finding is that homozygosity for recessive alleles of barley lpa1, not only reduced seed phytic acid by about 50%, but also seed total by about 15%. The low seed total P trait would be useful when grains or grain products are used for biofuel production or in feeds used in dairy or beef production. Future work will continue to study the genetics and biology of seed phytic acid, but even greater opportunity exists for progress in the genetics of seed total P. The beauty of forward genetics in this area of research and in other areas of plant biology is its potential as a tool of discovery.