OsNTL2 confers rice osmotic stress resilience through coordinated transcriptional regulation of the ASC-GSH redox cycle and cell wall biosynthesis.

Abstract

Drought, high salinity, and low temperatures impose osmotic stress, hindering water uptake and severely limiting plant growth and crop productivity. Osmotic stress not only perturbs cellular osmotic homeostasis but also disrupts multiple metabolic processes, including reactive oxygen species (ROS) metabolism. However, the transcriptional regulation underlying these redox processes in plants remains poorly understood. Here, we report that rice NAC WITH TRANS-MEMBRANE MOTIF1- LIKE 2 (OsNTL2) is required for tolerance to salt and osmotic stresses. DNA affinity purification-sequencing (DAP-seq) revealed that OsNTL2 directly targets key genes in the ascorbate-glutathione (ASC-GSH) redox cycle, including ascorbate peroxidase 2 (APX2), monodehydroascorbate reductase 1 (MDHAR1), glutathione reductase 2 (GR2), and glutathione peroxidase 5 (GPX5), as well as peroxidase 3/70 (PRX3/70), which function in the hydrogen peroxide catabolic process. Consistently, OsNTL2 activity was associated with enhanced ASC-GSH cycle enzyme activities, elevated ASC and GSH contents, and reduced ROS accumulation, as confirmed by histochemical staining. Furthermore, integrating DAP-seq with transcriptome analysis, we identified 325 direct transcriptional targets of OsNTL2, with a significant enrichment of genes involved in lignin and xylan biosynthesis. Notably, OsNTL2 bound directly to the promoters of, 4-coumarate-CoA ligase 5 (Os4CL5), and cinnamoyl-CoA reductase (OsCCR), activating their transcription. Correspondingly, stress-induced lignin, xylan, and cellulose accumulation was markedly reduced in ntl2 mutants but enhanced in OsNTL2-overexpressing lines. Together, these findings identify OsNTL2 as a key transcriptional regulator that coordinates the ASC-GSH redox cycle and cell wall biosynthesis to confer osmotic stress tolerance in rice.