Location: Crops Pathology and Genetics ResearchTitle: Identification of novel rice low phytic acid mutations via TILLING by sequencing) Author
Submitted to: Molecular Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/29/2014
Publication Date: 6/7/2014
Publication URL: http://link.springer.com/article/10.1007%2Fs11032-014-0127-y
Citation: Kim, S., Tai, T. 2014. Identification of novel rice low phytic acid mutations via TILLING by sequencing. Molecular Breeding. DOI: 10.1007/s11032-014-0127-y. Interpretive Summary: The majority of phosphorus, an important macronutrient, in plant seeds is found in the form of phytic acid. Phytic acid is not readily digested by human beings or non-ruminant livestock such as swine and poultry. Due to its chemical properties, phytic acid is also able to bind important mineral micronutrients such as iron and zinc. Developing seed crops which are low in phytic acid and have increased bioavailable phosphorus is an important goal for improving the nutritional quality of foods and animal feeds and lowering animal production costs. In this study, we have used information on genes involved in phytic acid metabolism in other plants to identify rice plants harboring gene mutations which result in reduced levels of seed phytic acid with corresponding increases in inorganic phosphorus which can be efficiently used by humans and livestock. These rice plants represent useful genetic materials for studying phytic acid metabolism and developing rice varieties with improved nutritional qualities.
Technical Abstract: Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate or InsP6) accounts for 75-85% of the total phosphorus in seeds. Low phytic acid (lpa) mutants exhibit decreases in seed InsP6 with corresponding increases in inorganic P which, unlike phytic acid P, is readily utilized by humans and monogastric animals. Since InsP6 may also reduce the bioavailability of essential mineral cations, development of lpa seed crops for animal feeds and whole-grain consumers is of significant interest and requires better understanding of the metabolism of InsP6 and the role it plays in other plant processes. To date well over 20 lpa mutants have been reported in a number of species, most of which have been identified through forward genetic screens. In this study, we have made use of a publicly available rice TILLING (Targeting of Local Lesions in Genomes) resource to identify four novel lpa mutations, two in one member of the inositol(1,3,4)P3 5-/6-kinase (Itpk) gene family (Os09g34300) and two in the previously reported OsMrp5 gene (Os04g04920). The mutations in Os09g34300 resulted in the significant reductions in InsP6 (46 and 68%) while those found in OsMrp5 were more modest (20 and 30%). The four mutants identified here will represent novel genetic resources for the genetic dissection of phytic acid metabolism in rice and the development of strategies for breeding lpa rice varieties.