Characterization onTaMPK14, an MAPK family gene of wheat, in modulating N-starvation response through regulating N uptake and ROS homeostasis

Key message Wheat MAPK geneTaMPK14is N starvation response and is crucial in modulating plant low-N stress tolerance. Improving plant N use efficiency (NUE) contributes largely to the sustainable crop production worldwide. In this study,TaMPK14, a mitogen-activated protein kinase (MAPK) family gene inT. aestivum, was characterized for the role in mediating N starvation response. TaMPK14 harbors conserved domain/motifs specified by the plant MAPK proteins. In vitro assay for kinase activity of TaMPK14 validated its phosphorylation nature.TaMPK14transcripts were upregulated in both roots and leaves under low-N treatment; moreover, the expression levels induced by N starvation were gradually restored following the N recovery progression. These results suggested transcriptional response ofTaMPK14upon the low-N stress. Compared with wild type (WT), theTaMPK14overexpressing lines inN. tabacumdisplayed improved growth and N accumulation traits under deficient-N treatment, which indicated the crucial roles of the MAPK gene in mediating N starvation response. Additionally, the lines treated by N starvation were shown to be improved on cellular ROS homeostasis, displaying higher antioxidant enzymes (AE) activities and less ROS accumulative amount than WT. The transcripts of nitrate transporter geneNtNRT2.1and those of AE genesNtSOD1,NtCAT1;2, andNtPOD4were significantly upregulated in N-deprivedTaMPK14lines; overexpression of them conferred plants enhanced N uptake capacity and AE activities, respectively. Moreover, RNA-seq datasets generated from N-deprived transgenic lines contained numerous differential genes involving modulating various biological process, cellular component, and molecular function. Together, our investigation suggested thatTaMPK14improves plant N starvation response through transcriptional regulation of distinct NRT and AE genes as well as modulation of associated biological processes.