The Auxin Biosynthetic Increases Grain Yield of Wheat.

Controlling the major auxin biosynthetic pathway to manipulate auxin content could be a target for genetic engineering of crops with desired traits, but little progress had been made because low or high auxin contents often cause developmental inhibition. Here, we performed a genome-wide analysis of bread wheat () to identify the Tryptophan Aminotransferase of Arabidopsis1/Tryptophan Aminotransferase-Related (TAA1/TAR) genes that function in the tryptophan-dependent pathway of auxin biosynthesis. Sequence mining together with gene cloning identified 15 genes, among which 12 and three genes were phylogenetically close to Arabidopsis () AtTAR2 and AtTAR3, respectively. had the most abundant transcripts in the genes and was expressed mainly in roots and up-regulated by low nitrogen (N) availability. Knockdown of caused vegetative and reproductive deficiencies and impaired lateral root (LR) growth under both high- and low-N conditions. Overexpressing in wheat enhanced LR branching, plant height, spike number, grain yield, and aerial N accumulation under different N supply levels. In addition, overexpressing in Arabidopsis elevated auxin accumulation in the primary root tip, LR tip, LR primordia, and cotyledon and hypocotyl and increased primary root length, visible LR number, and shoot fresh weight under high- and low-N conditions. Our results indicate that is critical for wheat growth and also shows potential for genetic engineering to reach the aim of improving the grain yield of wheat.