Genome-Wide Identification and Expression Profiling of Starch-Biosynthetic Genes in Common Wheat

Starch is synthesized through coordinated interactions of a suite of biosynthetic enzymes, including ADP-glucose pyrophosphorylases (TaAGP), granule-bound starch synthases (TaGBSS), starch synthases (TaSS), starch branching enzymes (TaSBE), and starch degradation enzymes (TaDBE). The genes involved in starch biosynthesis have not been extensively studied in common wheat. In an effort to isolate the sequences of genes responsible for starch biosynthesis in common wheat, we identified 57 genes. These genes included two types of TaAGPL located on wheat homoeologous groups 1 and 5; two types of TaAGPS located on groups 5 and 7; TaGBSSI located on chromosomes 4A, 7A, and 7D; TaGBSSII located on group 2; two types of TaISA located on groups 5 and 7; TaPUL located on group 7; three types of TaSBE located on groups 2 and 7; TaSSI located on group 7; TaSSII-1 located on group 1; TaSSII-2 located on group 6; TaSSII-3 located on group 7; TaSSIII-1 located on group 2; TaSSIII-2 located on group 1; and TaSSIV located on group 1. Wheat group 7 had the largest number of these genes. Phylogenetic analysis indicated that common wheat was closely related to Brachypodium, but relatively distant from rice and Sorghum. In silico expression-analysis in different tissues revealed that most of the genes were highly expressed in reproductive tissues, but expression was relatively low in all other tissues. Twelve genes (TaGBSSII-2, TaISA-5, TaSBE-2.1 and TaISA-7) were up-regulated after drought stress for 6 h, and only six genes (TaPUL-7 and TaISA-7) were up-regulated after heat stress for 6 h. This information will be useful for genetic manipulation of starch-biosynthesis genes to develop improved cultivars with high yield and good quality.