A Low Phytic Acid Barley Mutation Alters Seed Gene Expression

Abstract

Barley ( Hordeum vulgare L.) low phytic acid ( lpa ) mutants have reduced levels of seed phytate and increased concentrations of 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 d after anthesis in developing seeds homozygous either for the lpa mutation M955, or for its corresponding nonmutant, 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 upregulated genes. No 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 affect seed development and function through carbon transport and starch synthesis and may account for yield reductions previously reported for this mutation.