Unraveling the genetic basis of amino acid composition in dry Arabidopsis seeds

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Essential amino acids are necessary for human health but must come from dietary sources, as the human body cannot produce them. A lack of these essential amino acids in a diet leads to malnutrition. Much of the world's human and livestock populations rely on seeds for protein, but most staple crops seeds are deficient in several essential amino acids. Efforts to fortify the amino acid composition of staple crop seeds have had limited success since plants respond to induced protein composition alterations by activating a regulatory mechanism that "resets" it back to an original state. While beneficial to the plant growth and development, this mechanism has been a major hurdle to biofortification efforts. Fortunately, it is also known that different cultivars/varieties display natural variation in their seed amino acid composition, which means that the regulation of these compounds is genetically driven and thus should be amenable to manipulation. Therefore, this project aims to identify the key genes involved in this regulatory mechanism by analyzing hundreds of Arabidopsis strains, which display natural genetic and seed amino acid composition variation. Subsequently the potential role of the identified candidate genes will be tested using classical physiological and genetic approaches. Identifying new genetics targets will help facilitate the breeding of new crop varieties that can support our nation's and world's growing population. It is important to identify the genes that underlie the amino acid composition of dry seeds. Doing so will shed new light on a complex regulatory mechanism in plants as well as facilitate efforts to fortify staple seed crops. While much is known about amino acid metabolic pathways, little is known about their regulation, especially in seeds. So far, it is known that alterations to the composition of seed storage proteins (i.e., the major amino acid sink) lead to proteomic reprogramming and activation of a rebalancing mechanism, a response that suggests tight regulation of this trait. Seed amino acid composition varies substantially across genotypes within the same genus. This observation implies that the genetic architecture responsible for this natural variation includes, at least in part, the genes involved in responding to amino acid sink alteration and activation of the rebalancing mechanism. This project aims to elucidate key components of this genetic architecture in Arabidopsis thaliana using two approaches: (1) a GWAS on amino acid composition measured from dry seeds of an 800-accession association panel and (2) an amino acid/gene expression correlation-based network analysis of wildtype and two storage protein mutants with active rebalancing phenotypes. The candidate genes identified from each approach will be compared, and the top candidate genes will be tested for involvement in amino acid regulation via knockdown and overexpression experiments. The identified genetic regulators will provide new targets for breeding programs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.