Data from: Tissue-specific changes in apoplastic proteins and cell wall structure during cold acclimation of winter wheat crowns

The wheat (Triticum aestivum L.) crown is the critical organ of low temperature stress survival over winter. In cold-acclimated crowns, ice formation in the apoplast causes severe tissue disruption as it grows at the expense of intracellular water. While previous crown studies have shown the vascular transition zone (VTZ) to have a higher freezing sensitivity than the shoot apical meristem (SAM), the mechanism behind the differential freezing response is not fully understood. Cooling cold-acclimated crowns to –10 °C resulted in an absence of VTZ tetrazolium chloride staining, whereas the temperatures at which 50% of the SAM stained positive and 50% of plants recovered (LT50) were similar after cold acclimation for 21 (–16 °C) and 42 d (–20 °C) at 4 °C. Proteomic analysis of the apoplastic fluids identified dehydrins, vernalization-responsive proteins, and cold shock proteins preferentially accumulated in the SAM. In contrast, modifications to the VTZ centered on increases in pathogenesis-related proteins, anti-freeze proteins, and sugar hydrolyzing enzymes. Fourier transform infrared spectroscopy focal plane array analysis identified the biochemical modification of the cell wall to enhance methyl-esterified cross-linking of glucuronoarabinoxylans in the VTZ. These findings indicate that the SAM and VTZ express two distinct tissue-specific apoplastic responses during cold acclimation.

普通小麦（Triticum aestivum L.）的根颈是其越冬低温胁迫存活的关键器官。在冷驯化后的根颈中，质外体形成的冰晶会通过消耗细胞内水分不断扩张，造成严重的组织损伤。既往根颈相关研究表明，维管过渡区（vascular transition zone, VTZ）的冻害敏感性高于茎尖分生组织（shoot apical meristem, SAM），但二者冻害响应差异的具体机制尚未完全阐明。将经4℃冷驯化21天和42天的根颈冷却至-10℃时，VTZ未检测到四唑氯染色阳性信号；而SAM的半致死温度（LT50，即50%组织染色阳性及50%植株恢复的温度）分别为-16℃和-20℃，二者差异不显著。对质外体液进行蛋白质组学分析发现，脱水素、春化响应蛋白及冷休克蛋白在SAM中优先积累。与之相反，VTZ的蛋白修饰主要表现为病程相关蛋白、抗冻蛋白与糖水解酶的丰度上调。傅里叶变换红外光谱（Fourier transform infrared spectroscopy, FTIR）焦平面阵列（focal plane array, FPA）分析显示，VTZ的细胞壁发生了生化修饰，增强了葡糖醛酸阿拉伯木聚糖的甲酯化交联。上述研究结果表明，SAM与VTZ在冷驯化过程中呈现出两种截然不同的组织特异性质外体响应模式。