# Multilayered Transcriptional Regulation Underlying Salt Tolerance in Rapeseed (Brassica napus L.) Revealed by Integrated Physiological and Transcriptomic Analyses

## TL;DR

This study explores how rapeseed plants respond to salt stress, identifying key genes and regulatory networks that help them survive in salty soils.

## Contribution

The study reveals a multilayered regulatory framework involving lncRNA–mRNA interactions that underlie salt tolerance in rapeseed.

## Key findings

- Salt stress altered the activity of thousands of genes, including those involved in hormone signaling and antioxidant defense.
- Long non-coding RNAs were identified as key regulators linking stress responses and metabolic adaptation.
- Phenylpropanoid and lignin biosynthesis pathways were activated, suggesting reinforced cell walls and stress mitigation.

## Abstract

Soil salinity poses a significant threat to global crop production, diminishing plant growth and food security. Rapeseed is an important oil crop, but its productivity is often limited in salty soils. This study investigated the response of rapeseed plants to salt stress by examining alterations in plant growth, stress-induced damage, and gene activity. Increasing salt concentrations resulted in leaf yellowing, reduced growth, and elevated levels of detrimental molecules that damage plant cells. Concurrently, plants produced protective compounds to maintain water balance and mitigate injury. At the molecular level, thousands of genes exhibited altered activity under salt stress, particularly those involved in hormone signaling, antioxidant defense, salt transport within cells, and cell wall reinforcement. We also discovered a group of regulatory genetic molecules that help control these stress responses. Together, our findings show that salt tolerance in rapeseed depends on the coordinated action of multiple protective systems. This knowledge provides useful targets for developing new rapeseed varieties that can better withstand saline soils, helping to maintain crop yields and support sustainable agriculture in areas affected by salinity.

Soil salinity represents a significant abiotic constraint limiting the productivity and geographical expansion of rapeseed (Brassica napus L.), yet the coordination among the signaling, hormonal, metabolic, and regulatory layers underlying salt tolerance remains incompletely understood. This study elucidates the physiological, biochemical, and transcriptomic responses of B. napus inbred line 383-5 to moderate salt stress (100 mM NaCl at day 10), identifying key lncRNA–mRNA regulatory networks. Salt stress induced pronounced, dose-dependent growth inhibition, oxidative damage, and osmotic adjustment, accompanied by extensive transcriptional reprogramming. Genome-wide analyses identified 6215 differentially expressed protein-coding genes and 941 salt-responsive long non-coding RNAs (lncRNAs), revealing coordinated regulation of ion transport, redox homeostasis, phytohormone signaling, and secondary metabolism. Functional enrichment analyses highlighted the central involvement of abscisic acid and ethylene signaling pathways, MAPK cascades, membrane transporters, and antioxidant systems. Notably, salt stress strongly activated the phenylpropanoid and lignin biosynthesis pathways, suggesting reinforced cell wall remodeling and enhanced oxidative stress mitigation. Integration of lncRNA–mRNA regulatory networks further indicated that non-coding transcripts act as important modulators linking hormone signaling, redox balance, and metabolic adaptation. Collectively, these results reveal a multilayered and tightly synchronized regulatory framework underlying salinity tolerance in B. napus and provide valuable molecular targets for the genetic improvement of salt-resilient rapeseed cultivars.