Wheat miRNA member TaMIR2275 involves plant nitrogen starvation adaptation via enhancement of the N acquisition-associated process

Abstract

Plant miRNAs mediate diverse biological processes associating with growth, development, and environmental stress responses through regulating target genes at the posttranscriptional or translation level. In this study, TaMIR2275, a miRNA family member of wheat (T. aestivum), was subjected to functional characterization in mediation of the nitrogen (N) starvation response. TaMIR2275 targets eight genes that encode proteins involving various biological processes, including stress defense, transcriptional regulation, signaling transduction, and trafficking. Upon N starvation stress, TaMIR2275 showed gradually upregulated expression over a 24 h treatment and its induced transcripts were gradually restored along with a 24 h recovery treatment. In contrast, most of the target genes exhibited reverse expression pattern in response to the N starvation stress. These results suggest that the target genes are regulated by this miRNA largely through a cleavage mechanism. TaMIR2275 endowed plants improved growth features; the TaMIR2275 overexpression lines showed increased biomass and N accumulation whereas those with TaMIR2275 knockdown exhibited decreased biomass and plant N amount after N starvation compared with wild type. NtNRT2.1 and NtNRT2.2, two tobacco nitrate transporter (NRT) genes, showed modified expression in N-deprived TaMIR2275 overexpressors, suggesting their roles in modulation of the N acquisition. Transgene analysis confirmed these NRT genes to mediate the N uptake under N deprivation; the lines with NtNRT2.1 and NtNRT2.2 knockdwon displayed deteriorated growth, lowered N accumulation, and reduced biomass under N starvation treatment. Our results indicate that TaMIR2275 is essential in plant N deprivation response through transcriptional regulation of target genes that involve the N acquisition-associated process.