TaARR1, a cytokinin response regulator gene in Triticum aestivum, is essential in plant N starvation tolerance via regulating the N acquisition and N assimilation

Abstract

Plant N starvation response is closely associated with the N signaling components that involve transduction of the low-N cues. In this study, we functionally characterized TaARR1, a cytokinin (CK) response regulator gene in Triticum aestivum, in mediating the N starvation adaptation in plants. TaARR1 harbors two conserved domains specified by plant ARR family members; subcellular localization analysis indicated its target onto nucleus after endoplasmic reticulum assortment. TaARR1 displayed modified expression upon the N starvation stressor, showing upregulated expression in roots and leaves over a 27-h N starvation treatment and whose induced transcripts were gradually recovered along with progression of the N recovery treatment. The tobacco lines overexpressing TaARR1 displayed improved low-N stress tolerance, displaying enlarged phenotype, increased biomass and N accumulation, and enhanced glutamine synthetase (GS) activities compared with wild type (WT) following the N starvation treatment. Expression analysis on genes encoding the nitrate transporter (NRT) and GS proteins in Nicotiana tabacum revealed that NtNRT2.2 and NtGS3 are upregulated in expression in the N-deprived transgenic lines, whose expression patterns were contrasted to other above family genes that were unaltered on transcripts between the transgenic lines and WT. Transgene analysis validated the function of NtNRT2.2 and NtGS3 in regulating N accumulation, GS activity, growth traits, and N use efficiency in plants. These results suggested the internal connection between the TaARR1-mediated N starvation tolerance and the modified transcription of distinct N acquisition- and assimilation-associated genes. Our investigation together indicates that TaARR1 is essential in plant N starvation adaptation due to the gene function in transcriptionally regulating distinct NRT and GS genes that affect plant N uptake and assimilation under the N starvation condition.

Keywords

• wheat (Triticum aestivum L.)
• cytokinin response regulator
• gene expression
• N starvation
• functional characterization