Gene expression profiling for seed protein and oil synthesis during early seed development in soybean

Soybean (Glycine max L.) is one of the most important crops because of its high seed contents of protein and oil. However, little is known about the molecular regulation of seed filling during accumulation of seed protein and oil storage products. We identified soybean homologs of Arabidopsis genes involved in metabolic pathways of carbon precursors, protein, and oil, and analyzed gene expression patterns in immature seeds at 1 and 2 weeks after flowering (WAF). G. max undergoes two rounds of whole-genome duplication; the number of genes involved in the three synthesis pathways is more than two times higher than that in Arabidopsis. Among these genes, five were conserved as single-copy genes and 44 were high copy gene families consisting of more than seven homolog members. We identified five differentially expressed genes in immature seeds aged between 1 and 2 WAF, including CELL WALL INVERTASE, BRANCHED-CHAIN AMINO ACID TRANSAMINASE, AMINO ACID PERMEASE, ALDEHYDE REDUCTASE, and BIOTIN CARBOXYL CARRIER PROTEIN. Expression analysis of the duplicated genes on the synteny block revealed that the duplicated genes involved in protein synthesis had stronger positive correlations between their expression patterns than those of oil synthesis genes. This study provides novel insights into the molecular details of genes associated with soybean seed protein and oil synthesis pathways. These genes can be used as tools to improve seed nutrient composition.