, Volume 286, Issue 2, pp 119-133
Date: 23 Jun 2011

Identification of genes necessary for wild-type levels of seed phytic acid in Arabidopsis thaliana using a reverse genetics approach

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The majority of phosphorus (P) in seeds is found in phytic acid (InsP6) which accumulates as the mixed salt phytate. InsP6 is generally considered to be an anti-nutrient and the development of low phytic acid (lpa) seed crops is of significant interest. We have employed a reverse genetics approach to examine the impact of disrupting genes involved in inositol phosphate metabolism on Arabidopsis seed InsP6 levels. Our analysis revealed that knockout mutations in three genes (AtITPK1, AtITPK4, and AtMIK/At5g58730) reduced seed InsP6 in addition to knockouts of four previously reported genes (AtIPK1, AtIPK2β, AtMRP5, and At5g60760). Seeds of these lpa mutants also exhibited reduced germination under various stress conditions. The greatest reduction in InsP6 (>70%) was observed in atmrp5 seeds which were also among the least sensitive to the stresses examined. Expression analysis of the lpa genes revealed three distinct patterns in developing siliques consistent with their presumed roles. Disruption of each lpa gene resulted in changes in the expression in some of the other lpa genes indicating that transcription of lpa genes is modulated by other constituents of InsP6 metabolism. While all the lpa genes represent possible targets for genetic engineering of low phytate seed crops, mutations in AtMRP5, AtMIK, and At5g60760 may be most successful for conventional approaches such as mutation breeding.

Communicated by Peter Westhoff.