Data from: Large-scale proteomics of the cassava storage root and identification of a target gene to reduce post-harvest deterioration

Cassava (Manihot esculenta) is the most important root crop in the tropics, but rapid postharvest physiological deterioration (PPD) of the root is a major constraint to commercial cassava production. We established a reliable method for image-based PPD symptom quantification and used label-free quantitative proteomics to generate an extensive cassava root and PPD proteome. Over 2600 unique proteins were identified in the cassava root, and nearly 300 proteins showed significant abundance regulation during PPD. We identified protein abundance modulation in pathways associated with oxidative stress, phenylpropanoid biosynthesis (including scopoletin), the glutathione cycle, fatty acid α-oxidation, folate transformation, and the sulfate reduction II pathway. Increasing protein abundances and enzymatic activities of glutathione-associated enzymes, including glutathione reductases, glutaredoxins, and glutathione S-transferases, indicated a key role for ascorbate/glutathione cycles. Based on combined proteomics data, enzymatic activities, and lipid peroxidation assays, we identified glutathione peroxidase as a candidate for reducing PPD. Transgenic cassava overexpressing a cytosolic glutathione peroxidase in storage roots showed delayed PPD and reduced lipid peroxidation as well as decreased H2O2 accumulation. Quantitative proteomics data from ethene and phenylpropanoid pathways indicate additional gene candidates to further delay PPD. Cassava root proteomics data are available at www.pep2pro.ethz.ch for easy access and comparison with other proteomics data.

木薯（Manihot esculenta）是热带地区最为重要的块根作物，但其块根快速发生的采后生理劣变（postharvest physiological deterioration, PPD）是制约木薯商业化生产的核心瓶颈。本研究建立了一套可靠的基于图像的PPD症状量化方法，并采用无标记定量蛋白质组学（label-free quantitative proteomics）构建了覆盖范围广泛的木薯块根及PPD相关蛋白质组（proteome）。研究在木薯块根中共鉴定到超过2600种独特蛋白质，其中近300种蛋白质在PPD进程中丰度发生显著调控变化。研究人员在与氧化应激、苯丙烷类生物合成（包括东莨菪素（scopoletin））、谷胱甘肽循环、脂肪酸α-氧化、叶酸转化以及硫酸盐还原II通路相关的通路中，鉴定到了蛋白质丰度的调控特征。谷胱甘肽相关酶类（包括谷胱甘肽还原酶、谷氧还蛋白与谷胱甘肽S-转移酶）的蛋白质丰度与酶活性均显著上升，提示抗坏血酸/谷胱甘肽循环在PPD进程中发挥关键调控作用。基于整合的蛋白质组学数据、酶活性检测结果与脂质过氧化（lipid peroxidation）实验分析，本研究将谷胱甘肽过氧化物酶鉴定为可缓解PPD的候选作用靶点。在贮藏块根中过表达胞质谷胱甘肽过氧化物酶的转基因木薯（transgenic cassava），表现出PPD延迟发生、脂质过氧化水平降低以及过氧化氢（H₂O₂）积累量减少的表型。基于乙烯（ethene）与苯丙烷通路的定量蛋白质组学数据，本研究还筛选得到可进一步延缓PPD进程的其他候选基因。木薯块根蛋白质组数据已上传至www.pep2pro.ethz.ch，以供研究人员便捷获取并与其他蛋白质组数据进行比对分析。