Transcriptomics-proteomics analysis reveals the role of SiNRX1 in regulating drought stress in foxtail millet (Setaria italica L.)

Nucleoredoxin (NRX), a member of the thioredoxin (TRX) superfamily, plays a crucial role in regulating plant growth and development, as well as in responses to both abiotic and biotic stresses. However, its contribution to drought resistance in foxtail millet remains unclear. In this study, the SiNRX1 of foxtail millet was knocked out using CRISPR/Cas9 system, and the drought resistance of sinrx1 mutants was identified at both the germination stage and the seedling stage. Moreover, through transcriptome sequencing and data-independent acquisition (DIA) quantitative proteomics determination of sinrx1 mutants and wild types (WT) at the seedling stage under drought and control conditions, the molecular mechanism of SiNRX1 regulating drought resistance was preliminarily analyzed. The results indicated that after 7 days of simulated drought treatment during the germination period, the germination rate, root length and bud length of the sinrx1 mutant decreased significantly in comparison with the WT. During the seedling stage under drought stress, the survival rate, chlorophyll content, proline content, peroxidase (POD) activity and catalase (CAT) activity of the sinrx1 mutant decreased markedly compared to those of the WT plants. However, the malondialdehyde (MDA) content of the sinrx1 mutant was significantly higher than that of the WT. This indicates that, during the germination and seedling stages, the drought resistance of the sinrx1 mutant decreased significantly compared to that of the WT. The transcriptome findings suggested that the 2253 differentially expressed genes (DEGs) (1179 up-regulated DEGs and 1074 down-regulated DEGs) are drought-responsive genes specifically influenced by SiNRX1. The 2253 DEGs were significantly enriched in pathways including phenylalanine, tyrosine and tryptophan biosynthesis, plant hormone signal transduction, phenylpropanoid biosynthesis, and plant-pathogen interaction. The proteomic results suggests that the 155 differentially expressed proteins (DEPs) (127 up-regulated DEPs and 28 down-regulated DEPs) are drought-responsive proteins specifically influenced by SiNRX1. The 155 DEPs were significantly enriched in pathways including biosynthesis of secondary metabolites, brassinosteroid biosynthesis, metabolic pathways, and phenylpropanoid biosynthesis. Moreover, 2253 DEGs and 155 DEPs were significantly and jointly enriched in the phenylpropanoid biosynthesis pathway. This study provides theoretical guidance for analyzing the drought resistance mechanisms of foxtail millet plants and for drought-resistance breeding.