Dual Regulation of DNA Methylation Orchestrates the Saline-Alkali Stress Response in Salt-Tolerant Brassica napus

Soil salinization is a threat to global agriculture.
This study
used whole-genome bisulfite sequencing and transcriptomics to explore
epigenetic regulation in salt-tolerant Brassica napus (cv. Huayouza 62) under NaCl (salt), Na2CO3 (alkali), and combined salt-alkali stresses. All stresses induced
genome-wide DNA hypermethylation (combined > alkali > salt).
The Cn
subgenome had significant methylation changes (most at CHH, then at
CHG), with more differentially methylated regions in transposable
elements than protein-coding genes. Hypermethylation, driven by DNA
methyltransferases (e.g., DRM2), inhibited growth by repressing photosynthetic
genes (RBCS-1A, RBCS-1B). B. napus adapted via targeted demethylation activated
stress resistance (ROS scavenging under salt, redox buffering under
alkali, and protein homeostasis under combined stress). 5-Azacytidine
validation confirmed that methylation balances photosynthesis and
stress response, clarifying the epigenetic network and providing strategies
for crop stress resistance improvement.

土壤盐渍化是全球农业面临的重大威胁。本研究采用全基因组亚硫酸氢盐测序（whole-genome bisulfite sequencing）与转录组学（transcriptomics）技术，探究了华油杂62号耐盐甘蓝型油菜（Brassica napus cv. Huayouza 62）在NaCl（盐胁迫）、Na₂CO₃（碱胁迫）及复合盐碱胁迫下的表观遗传调控机制。三种胁迫均可诱导全基因组DNA高甲基化，且诱导程度表现为复合胁迫 > 碱胁迫 > 盐胁迫。Cn亚基因组发生了显著的甲基化变化，其甲基化位点主要富集于CHH区域，其次为CHG区域；且转座元件（transposable elements）上的差异甲基化区域数量显著多于蛋白编码基因。由DNA甲基转移酶（DNA methyltransferases，如DRM2）介导的DNA高甲基化，通过抑制光合相关基因（RBCS-1A、RBCS-1B）的表达抑制植株生长。甘蓝型油菜可通过靶向去甲基化激活抗逆通路：盐胁迫下清除活性氧（ROS）、碱胁迫下维持氧化还原稳态、复合胁迫下保障蛋白质稳态。5-氮杂胞苷（5-Azacytidine）验证实验证实，DNA甲基化可平衡光合过程与胁迫响应通路，阐明了表观调控网络，并为作物抗逆性状改良提供了可行策略。