TaLBD1, a LOB Transcription Factor Gene In T. Aestivum, Improves Plant N Starvation Adaptation Via Modulating N Acquisition-Associated Processes
Abstract Members of transcription factor (TF) families contribute largely to plant N starvation tolerance by regulating downstream stress defensive genes. In this study, we characterized TaLBD1, a Lateral Organ Boundary (LOB) TF gene in T. aestivum, in regulating plant low-N stress adaptation. TaLBD1 harbors the conserved domains specified by plant LOB proteins, targeting onto nucleus after endoplasmic reticulum (ER) assortment. The TaLBD1 transcripts were response sensitively to N starvation (NS) signaling, showing to be gradually upregulated in aerial and root tissues over a 27-h NS condition. The N. tabacum lines overexpressing TaLBD1 improved phenotype, root system architecture (RSA) establishment, biomass, and N contents of plants under NS treatment. The nitrate transporter gene NtNRT2.4 and PIN-FORMED gene NtPIN6 significantly upregulated in expression in NS-challenged lines; knockdown expression of NtNRT2.4 decreased N uptake and that of NtPIN6 alleviated RSA establishment relative to WT. These results validate the function of NRT and PIN genes in regulating plant N uptake and RSA behavior. RNA-seq analyses revealed that a quantity of genes modify expression in N-deprived lines overexpressing TaLBD1, which enriched into functional groups of signal transduction, transcription, protein biosynthesis, primary or secondary metabolism, and stress defensiveness. These findings suggested that the TaLBD1-improved NS adaptation attributes largely to its role in transcriptionally regulating NRT and PIN genes as well as in modulating those functional in various biological processes. TaLBD1 is a crucial regulator in plant N starvation tolerance and valuable target for molecular breeding high N use efficiency (NUE) crop cultivars.