Nitrate dose-responsive transcriptome analysis identifies transcription factors and small secreted peptides involved in nitrogen response in Tartary buckwheat.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is an economically important pseudocereal crop, which can adapt well to extreme environments, including low nitrogen (LN) stress. However, little is known regarding the associated molecular mechanisms. In this study, the molecular mechanism of Tartary buckwheat roots in response to different doses of nitrate was investigated by combining physiological changes with transcriptional regulatory network. LN improved elongation and branching of lateral roots, indicating that the plasticity of lateral roots drives the adaption of Tartary buckwheat under LN condition. The roots of the seedlings that were cultivated under four N conditions were selected for RNA-Seq analysis. In total 1686 nitrate dose-responsive genes were identified. Of these genes, 16 genes encoding N transporters showed response to N availability, and they may play important roles in N transport and root system architecture in Tartary buckwheat roots. 108 transcription factors (TFs) showed dose-response to N availability, and they may regulate N response and root growth under varied N conditions by modulating the expression of N transporters. A NIN-like protein, FtNLP7, was identified and it may contribute to the transcriptional regulation of N transporters. Furthermore, 81 N-responsive genes were identified as the small secreted peptides (SSPs). 48 N-responsive SSPs were annotated as hypothetical proteins and they may be the species-specific proteins of Tartary buckwheat. This paper provides useful information for further investigation of the mechanisms underlying the adaptation of Tartary buckwheat under N-deficient condition.