|Kim, Sang Ic|
Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2011
Publication Date: 6/23/2011
Citation: Kim, S., Tai, T. 2011. Identification of genes necessary for wild-type levels of seed phytic acid in Arabidopsis thaliana using a reverse genetics approach. Molecular Genetics and Genomics. 286:119-133.
Technical Abstract: The majority of phosphorus (P) in seeds is found in the form of phytic acid (InsP6) which 22 accumulates as the mixed salt phytate and accounts for > 60% of total seed P. InsP6 is generally 23 considered to be an anti-nutrient and the development of low phytic acid (lpa) seed crops is of 24 significant interest. We have employed a reverse genetics approach to examine the impact of 25 disrupting genes involved in inositol phosphate metabolism on the InsP6 content of Arabidopsis 26 seeds. Our analysis revealed that knockout mutations in three genes (AtITPK1, AtITPK4, and 27 At5g58730 - the ortholog of maize lpa3) reduced InsP6 content of seeds in addition to knockouts 28 of four previously reported genes (AtIPK1, AtIPK2ß, AtMRP5, and At5g60760 - the ortholog of 29 rice OsLpa1). Expression analysis of the lpa genes revealed three distinct patterns in developing 30 siliques consistent with their presumed roles. Germination assays indicated that all lpa mutant 31 seeds were more sensitive than wild-type to abiotic stresses; however, differences in sensitivity 32 were observed. The greatest reduction (>70%) in InsP6 was observed in atmrp5 seeds which 33 were also among the least sensitive to the stresses examined. These findings are consistent with 34 the probable role of AtMRP5 in transport/accumulation of InsP6 rather than in biosynthesis as is 35 the case for most, if not all, of the other lpa genes. While all the lpa genes represent possible 36 targets for genetic engineering of low phytate seed crops, mutations in AtMRP5 orthologs may 37 be most successful for conventional approaches such as mutation breeding.