In plants, the plasticity of root architecture in response to nitrogen availability largely determines nitrogen acquisition efficiency. One poorly understood root growth response to low nitrogen availability is an observed increase in the number and length of lateral roots (LRs). Here, we show that low nitrogen-induced Arabidopsis lateral root growth depended on the function of the auxin biosynthesis gene TAR2 (tryptophan aminotransferase related 2). TAR2 was expressed in the pericycle and the vasculature of the mature root zone near the root tip, and was induced under low nitrogen conditions. In the wild type plants, low nitrogen stimulated auxin accumulation in the non-emerged LR primordia with >3 cell layers and LR emergence. Conversely, these low nitrogen-mediated auxin accumulation and root growth responses were impaired in the tar2-c null mutant. Overexpression of TAR2 increased LR numbers under both high and low nitrogen conditions. Our results suggest that TAR2 is required for reprogramming root architecture in response to low nitrogen conditions. This finding suggests a new strategy for improving nitrogen use efficiency through the engineering of TAR2 expression in roots.

 

Keywords:Arabidopsis;low nitrogen stress;lateral root;auxin biosynthesis;TAR2