Xie Yang, Xu Liang, Wang Yan, Fan Lianxue, Chen Yinglong, Tang Mingjia, Luo Xiaobo, Liu Liwang
1National Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Horticultural Crop Biology and Genetic Improvement (East China) of MOA, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095 PR China.
2The UWA Institute of Agriculture, UWA School of Agriculture and Environment, The University of Western Australia, Perth, WA 6001 Australia.
Hortic Res. 2018 Oct 1;5:51. doi: 10.1038/s41438-018-0057-7. eCollection 2018.
The fleshy taproot of radish is an important storage organ determining its yield and quality. Taproot thickening is a complex developmental process in radish. However, the molecular mechanisms governing this process remain unclear at the proteome level. In this study, a comparative proteomic analysis was performed to analyze the proteome changes at three developmental stages of taproot thickening using iTRAQ approach. In total, 1862 differentially expressed proteins (DEPs) were identified from 6342 high-confidence proteins, among which 256 up-regulated proteins displayed overlapped accumulation in S1 (pre-cortex splitting stage) vs. S2 (cortex splitting stage) and S1 vs. S3 (expanding stage) pairs, whereas 122 up-regulated proteins displayed overlapped accumulation in S1 vs. S3 and S2 vs. S3 pairs. Gene Ontology (GO) and pathway enrichment analysis showed that these DEPs were mainly involved in several processes such as "starch and sucrose metabolism", "plant hormone signal transduction", and "biosynthesis of secondary metabolites". A high concordance existed between iTRAQ and RT-qPCR at the mRNA expression levels. Furthermore, association analysis showed that 187, 181, and 96 DEPs were matched with their corresponding differentially expressed genes (DEGs) in S1 vs. S2, S1 vs. S3, and S2 vs. S3 comparison, respectively. Notably, several functional proteins including cell division cycle 5-like protein (CDC5), expansin B1 (EXPB1), and xyloglucan endotransglucosylase/hydrolase protein 24 (XTH24) were responsible for cell division and expansion during radish taproot thickening process. These results could facilitate a better understanding of the molecular mechanism underlying taproot thickening, and provide valuable information for the identification of critical genes/proteins responsible for taproot thickening in root vegetable crops.
萝卜的肉质直根是决定其产量和品质的重要贮藏器官。直根增粗是萝卜中一个复杂的发育过程。然而，在蛋白质组水平上，调控这一过程的分子机制仍不清楚。在本研究中，采用iTRAQ方法进行了比较蛋白质组学分析，以分析直根增粗三个发育阶段的蛋白质组变化。总共从6342个高可信度蛋白质中鉴定出1862个差异表达蛋白（DEP），其中256个上调蛋白在S1（皮层分裂前期）与S2（皮层分裂期）以及S1与S3（膨大期）组对中表现出重叠积累，而122个上调蛋白在S1与S3以及S2与S3组对中表现出重叠积累。基因本体（GO）和通路富集分析表明，这些DEP主要参与“淀粉和蔗糖代谢”、“植物激素信号转导”和“次生代谢物的生物合成”等多个过程。在mRNA表达水平上，iTRAQ和RT-qPCR之间存在高度一致性。此外，关联分析表明，在S1与S2、S1与S3以及S2与S3的比较中，分别有187、181和96个DEP与其相应的差异表达基因（DEG）相匹配。值得注意的是，包括细胞分裂周期5样蛋白（CDC5）、扩张蛋白B1（EXPB1）和木葡聚糖内转糖基酶/水解酶蛋白24（XTH24）在内的几种功能蛋白在萝卜直根增粗过程中负责细胞分裂和扩张。这些结果有助于更好地理解直根增粗的分子机制，并为鉴定根菜类作物中负责直根增粗的关键基因/蛋白提供有价值的信息。
