BACKGROUND Pear fruit exhibit a single sigmoid pattern during development, while peach and strawberry fruits exhibit a double sigmoid pattern. However, little is known about the differences between these two patterns. RESULTS In this study, fruit weights were measured and paraffin sections were made from fruitlet to maturated pear, peach, and strawberry samples. Results revealed that both single and double sigmoid patterns resulted from cell expansion, but not cell division. Comparative transcriptome analyses were conducted among pear, peach, and strawberry fruits at five fruit enlargement stages. Comparing the genes involved in these intervals among peaches and strawberries, 836 genes were found to be associated with all three fruit enlargement stages in pears (Model I). Of these genes, 25 were located within the quantitative trait locus (QTL) regions related to fruit weight and 90 were involved in cell development. Moreover, 649 genes were associated with the middle enlargement stage, but not early or late enlargement in pears (Model II). Additionally, 22 genes were located within the QTL regions related to fruit weight and 63 were involved in cell development. Lastly, dual-luciferase assays revealed that the screened bHLH transcription factors induced the expression of cell expansion-related genes, suggesting that the two models explain the single sigmoid pattern. CONCLUSIONS Single sigmoid patterns are coordinately mediated by Models I and II, thus, a potential gene regulation network for the single sigmoid pattern was proposed. These results enhance our understanding of the molecular regulation of fruit size in Rosaceae.

中文翻译：

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梨，桃和草莓果实发育的比较转录组分析为单一乙状结肠模式提供了新见解。

背景技术梨果实在发育过程中表现出单一的S形图案，而桃和草莓果实表现出双重的S形图案。但是，关于这两种模式之间的差异知之甚少。结果在这项研究中，测量了水果的重量，并从小果实到成熟的梨，桃和草莓样品制作了石蜡切片。结果显示单乙状乙状结肠和双乙状乙状结肠都是由细胞扩张引起的，而不是细胞分裂引起的。在梨，桃和草莓果实的五个果实扩大阶段进行了转录组比较分析。比较桃和草莓在这些间隔中涉及的基因，发现了836个基因与梨的所有三个果实膨大阶段有关（模型I）。在这些基因中 25个位于与果实重量有关的数量性状基因座（QTL）区域内，其中90个与细胞发育有关。此外，有649个基因与梨的中等扩增阶段有关，但与早期或晚期扩增无关（模型II）。另外，在与果实重量有关的QTL区域内定位有22个基因，其中63个基因参与细胞发育。最后，双荧光素酶测定法表明，筛选的bHLH转录因子诱导了细胞扩张相关基因的表达，表明这两种模型解释了单一的乙状结肠模式。结论单一乙状结肠模式由模型I和II协调介导，因此，提出了一种潜在的基因调控网络。这些结果增强了我们对蔷薇科果实大小分子调控的理解。