State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, 210095, China.
BMC Genomics. 2017 Nov 22;18(1):896. doi: 10.1186/s12864-017-4290-5.
Parthenocarpy is an excellent agronomic trait that enables crops to set fruit in the absence of pollination and fertilization, and therefore to produce seedless fruit. Although parthenocarpy is widely recognized as a hormone-dependent process, hormone-insensitive parthenocarpy can also be observed in cucumber; however, its mechanism is poorly understood. To improve the global understanding of parthenocarpy and address the hormone-insensitive parthenocarpy shown in cucumber, we conducted a physiological and proteomic analysis of differently developed fruits.
Physiological analysis indicated that the natural hormone-insensitive parthenocarpy of 'EC1' has broad hormone-inhibitor resistance, and the endogenous hormones in the natural parthenocarpy (NP) fruits were stable and relatively lower than those of the non-parthenocarpic cultivar '8419 s-1.' Based on the iTRAQ technique, 683 fruit developmental proteins were identified from NP, cytokinin-induced parthenocarpic (CP), pollinated and unpollinated fruits. Gene Ontology (GO) analysis showed that proteins detected from both set and aborted fruits were involved in similar biological processes, such as cell growth, the cell cycle, cell death and communication. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that 'protein synthesis' was the major biological process that differed between fruit set and fruit abortion. Clustering analysis revealed that different protein expression patterns were involved in CP and NP fruits. Forty-one parthenocarpy-specialized DEPs (differentially expressed proteins) were screened and divided into two distinctive groups: NP-specialized proteins and CP-specialized proteins. Furthermore, qRT-PCR and western blot analysis indicated that NP-specialized proteins showed hormone- or hormone-inhibitor insensitive expression patterns in both ovaries and seedlings.
In this study, the global molecular regulation of fruit development in cucumber was revealed at the protein level. Physiological and proteomic comparisons indicated the presence of hormone-independent parthenocarpy and suppression of fruit abortion in cucumber. The proteomic analysis suggested that hormone-independent parthenocarpy is regulated by hormone-insensitive proteins such as the NP-specialized proteins. Moreover, the regulation of fruit abortion suppression may be closely related to protein synthesis pathways.
单性结实是一种极好的农艺性状，使作物能够在没有授粉和受精的情况下结实，从而产生无籽果实。尽管单性结实被广泛认为是一种依赖激素的过程，但在黄瓜中也可以观察到激素不敏感的单性结实；然而，其机制尚不清楚。为了提高对单性结实的全球认识，并解决黄瓜中表现出的激素不敏感的单性结实问题，我们对不同发育阶段的果实进行了生理和蛋白质组学分析。
生理分析表明，‘EC1’的天然激素不敏感单性结实具有广泛的激素抑制剂抗性，天然单性结实（NP）果实中的内源激素稳定且相对低于非单性结实品种‘8419 s-1’。基于 iTRAQ 技术，从 NP、细胞分裂素诱导的单性结实（CP）、授粉和未授粉果实中鉴定出 683 种果实发育蛋白。基因本体论（GO）分析表明，从设定和流产果实中检测到的蛋白质都参与了类似的生物学过程，如细胞生长、细胞周期、细胞死亡和通讯。京都基因与基因组百科全书（KEGG）分析表明，“蛋白质合成”是果实设定和果实流产之间的主要生物学过程。聚类分析表明，CP 和 NP 果实涉及不同的蛋白质表达模式。筛选出 41 种单性结实特异性差异表达蛋白（DEPs），并分为两类：NP 特异性蛋白和 CP 特异性蛋白。此外，qRT-PCR 和 Western blot 分析表明，NP 特异性蛋白在卵巢和幼苗中均表现出激素或激素抑制剂不敏感的表达模式。
在这项研究中，揭示了黄瓜果实发育的全局分子调控在蛋白质水平上。生理和蛋白质组学比较表明，黄瓜存在激素不敏感的单性结实和果实败育抑制。蛋白质组学分析表明，激素不敏感的单性结实受激素不敏感蛋白（如 NP 特异性蛋白）的调节。此外，果实败育抑制的调控可能与蛋白质合成途径密切相关。
