Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, College of Resources and Environmental Sciences, Hunan Agricultural University, Changsha, China.
Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, National Engineering Laboratory on Soil and Fertilizer Resources Efficient Utilization, Hunan Provincial Key Laboratory of Nutrition in Common University, Changsha, 410128, China.
BMC Plant Biol. 2019 Jun 26;19(1):280. doi: 10.1186/s12870-019-1895-7.
The xylem sap of vascular plants primarily transports water and mineral nutrients from the roots to the shoots and also transports heavy metals such as cadmium (Cd). Proteomic changes in xylem sap is an important mechanism for detoxifying Cd by plants. However, it is unclear how proteins in xylem sap respond to Cd. Here, we investigated the effects of Cd stress on the xylem sap proteome of Brassica napus using a label-free shotgun proteomic approach to elucidate plant response mechanisms to Cd toxicity.
We identified and quantified 672 proteins; 67% were predicted to be secretory, and 11% (73 proteins) were unique to Cd-treated samples. Cd stress caused statistically significant and biologically relevant abundance changes in 28 xylem sap proteins. Among these proteins, the metabolic pathways that were most affected were related to cell wall modifications, stress/oxidoreductases, and lipid and protein metabolism. We functionally validated a plant defensin-like protein, BnPDFL, which belongs to the stress/oxidoreductase category, that was unique to the Cd-treated samples and played a positive role in Cd tolerance. Subcellular localization analysis revealed that BnPDFL is cell wall-localized. In vitro Cd-binding assays revealed that BnPDFL has Cd-chelating activity. BnPDFL heterologous overexpression significantly enhanced Cd tolerance in E. coli and Arabidopsis. Functional disruption of Arabidopsis plant defensin genes AtPDF2.3 and AtPDF2.2, which are mainly expressed in root vascular bundles, significantly decreased Cd tolerance.
Several xylem sap proteins in Brassica napus are differentially induced in response to Cd treatment, and plant defensin plays a positive role in Cd tolerance.
维管植物的木质部汁液主要将水和矿物质养分从根部输送到地上部分，同时也将重金属如镉（Cd）输送到地上部分。木质部汁液中的蛋白质组变化是植物解毒 Cd 的重要机制。然而，木质部汁液中的蛋白质如何响应 Cd 尚不清楚。在这里，我们使用无标记shotgun 蛋白质组学方法研究了 Cd 胁迫对油菜木质部汁液蛋白质组的影响，以阐明植物对 Cd 毒性的响应机制。
我们鉴定和定量了 672 种蛋白质；67%预测为分泌性，11%（73 种蛋白质）为 Cd 处理样品所特有。Cd 胁迫导致 28 种木质部汁液蛋白的丰度发生了统计学上显著且具有生物学意义的变化。在这些蛋白质中，受影响最大的代谢途径与细胞壁修饰、应激/氧化还原酶以及脂质和蛋白质代谢有关。我们对一种植物防御素样蛋白 BnPDFL 进行了功能验证，BnPDFL 属于应激/氧化还原酶类，是 Cd 处理样品所特有的，在 Cd 耐受中发挥积极作用。亚细胞定位分析表明 BnPDFL 定位于细胞壁。体外 Cd 结合实验表明 BnPDFL 具有 Cd 螯合活性。BnPDFL 异源过表达显著增强了大肠杆菌和拟南芥的 Cd 耐受性。拟南芥植物防御素基因 AtPDF2.3 和 AtPDF2.2 的功能缺失，主要在根部维管束中表达，显著降低了 Cd 耐受性。
油菜中几种木质部汁液蛋白对 Cd 处理有差异诱导，植物防御素在 Cd 耐受中发挥积极作用。
