TaLBD1, a LOB transcription factor gene in T. aestivum, confers plant adaptation to low-N stress via modulating N acquisition-associated processes

Abstract

Distinct members of transcription factor (TF) families act as the critical mediators in plant low-N stress response by regulating transcription of the stress defensive-associated genes. In this study, TaLBD1, a member of the Lateral Organ Boundary (LOB) TF family in Triticum aestivum, was characterized for its role in modulating the plant adaptation to N deprivation condition. TaLBD1 protein harbors the conserved domains that are shared by the plant LOB TF proteins and targets onto nucleus after endoplasmic reticulum (ER) assortment. The transcripts of TaLBD1 were found to be responsive to N starvation stress in both roots and leaves, as shown by their significantly upregulated transcripts during a 27 h regime of N starvation treatment. The tobacco lines with overexpression of TaLBD1 indicated that it can confer to plants an improved phenotype, root system architecture (RSA), biomass, and N accumulation under N starvation treatment. The expression levels of NtRNT2.4 and NtPIN6, two genes encoding nitrate transporter (NRT) and PIN-FORMED proteins in N. tabacum, were found to be significantly upregulated in expression in the N-deprived transgenic lines overexpressing TaLBD1. Knockdown expression on NtRNT2.4 and NtPIN6 led to plants for an alleviation on the N accumulation and RSA establishment relative to WT, suggesting that they are involved in the regulation of plant and RSA formation, respectively. Transcriptome analyses revealed a number of up- and down- regulated genes in the N-pdeprived transgenic lines with TaLBD1 overexpression, which are involved in biological processes associated with signal transduction, transcription, protein biosynthesis, primary or secondary metabolism, and stress defensiveness. Our results together suggested that TaLBD1 positively regulates plant N starvation tolerance through improvement of N uptake and RSA formation. It is valuable in efforts for molecular engineering the high N use efficiency (NUE) cultivars of cereal crops. The member of the LOB transcription factor family TaLBD1 in T. aestivum confers plant tolerance to N starvation stress via modulating N uptake and RSA establishment.