Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2006
Publication Date: 7/14/2007
Citation: Bowen, D., Gutheri, M., Fu, J., Souza, E.J., Raboy, V. 2007. A Low Phytic Acid Barley Mutation Alters Gene Expression in Early Seed Development. Crop Science. 47(S2):S149-S159. Interpretive Summary: Low phytic acid seed crops are developed to improve human and animal nutrition through increasing the available phosphorus and micronutrients in the seed. The low phytic acid crops also have been shown to reduce phosphorus in animal waste, important for reducing the biological impact of animal waste steams. We compared low phytic acid barley to normal (wild type) barley to understand how these mutations affect other biological processes in the plant. Reduced gene expression in the low phytic acid barley was observed for functions important to carbohydrate and cell wall metabolism, cytokinin and ethylene signaling, and transport functions. This may explain some of the yield reduction observed in some of the low phytic acid mutations. It also suggests methods for countering those effects or perhaps use of the phytic acid pathway to enhance yields of crops in the future.
Technical Abstract: Barley (Hordeum vulgare L.) low phytic acid (lpa) mutants have reduced levels of seed phytate, the most abundant form of phosphorus in seeds, and increases in seed inorganic phosphorus. To understand how lpa mutations affect metabolic and developmental processes during seed growth, gene expression experiments were performed using oligonucleotide microarrays. Differential gene expression was assayed at 7 days after anthesis in developing seeds homozygous either for the lpa mutation M955, or for its corresponding non-mutant, wild-type allele. Homozygosity for M955 blocks phytate accumulation throughout seed development, resulting in a ~90% reduction in mature seed phytate. Consistent and substantial differential expression was observed for 38 genes (probesets) representing various cellular processes and unknown functions. The majority of differentially expressed genes showed decreased expression with a much smaller proportion of up-regulated genes. No major changes in expression of genes thought to be directly involved in the synthesis of phytate were observed. Reduced expression was observed for functions important to carbohydrate and cell wall metabolism, cytokinin and ethylene signaling, and transport functions. These results reflect the interconnection of phosphorus, inositol phosphate and sugar metabolism and signaling networks regulating these metabolic and developmental pathways. The M955 lpa mutation appears to effect seed development and function through carbon transport and starch synthesis and may account for yield reductions previously reported for this mutation.