Wheat amino acid transporters highly expressed in grain cells regulate amino acid accumulation in grain

Amino acids are delivered into developing wheat grains to support the accumulation of storage proteins in starchy endosperm, and transporters play important roles regulating this process. RNA-seq, RT-qPCR, promoter-GUS assays showed that three amino acid differentially expressed endosperm transfer cells ( TaAAP2 ), TaAAP13 aleurone embryo grain TaAAP21 respectively. Yeast complementation revealed all can transport a broad spectrum acids. RNAi-mediated suppression expression did not reduce total nitrogen content whole grain, but significantly altered composition distribution metabolites with increasing concentrations some (notably glutamine glycine) from outer inner compared wild type. Overexpression under endosperm-specific HMW-GS (high molecular weight glutenin subunit) promoter increased size, concentration, thousand weight, indicating sink strength for was by manipulation transporters. However, number reduced, suggesting source remobilized leaves is limiting factor productivity. Therefore, simultaneously loading phloem delivery spike would be required increase protein while maintaining yield.