Molecular characterization, expression and functional analysis of the amino acid transporter gene family OsAATs in rice

Nitrogen (N) is one of the most important limiting factors for plant growth and development. Amino acids are the major source of organic N, which is converted from inorganic N absorbed by plant roots from the soil. Amino acid transporters are the principal mediators of organic N distribution and important regulators of resource allocation in plants. Although the complete genomic sequence of rice has already been released, there is still little known about amino acid transporter genes in rice. In this study, 79 OsAAT genes were identified by a database search of the rice genome based upon HMM profiles. A bioinformatics analysis of the complete set of OsAAT genes is presented, including chromosomal location, phylogenetic analysis, gene structure, protein analysis, conserved motifs, protein structures and cis-element analysis of the promoters. In addition, the comprehensive expression profile of OsAAT genes in rice tissues/organs under N starvation conditions was investigated by real-time PCR analysis. Diverse expression patterns of OsAAT genes indicated diverse biological functions of the amino acid transporters and the important roles of OsAAT genes in N uptake, metabolism and distribution during N starvation. The evaluation of yield and carbon (C) and N content of osaat knockout mutants also suggested the important roles of the OsAAT5, OsAAT7, OsAAT24, OsAAT49 and OsAAT60 genes in yield and biomass production and C and N metabolism and distribution in rice plants.