School of Life Science, Huaibei Normal University, Huaibei, 10000, China.
Horticulture Department, University of Wisconsin, Madison, WI, 53706, USA.
Theor Appl Genet. 2022 Jun;135(6):2101-2119. doi: 10.1007/s00122-022-04100-4. Epub 2022 May 7.
Fruit skin netting in cucumber (Cucumis sativus) is associated with important fruit quality attributes. Two simply inherited genes H (Heavy netting) and Rs (Russet skin) control skin netting, but their molecular basis is unknown. Here, we reported map-based cloning and functional characterization of the candidate gene for the Rs locus that encodes CsSHINE1 (CsSHN1), an AP2 domain containing ethylene-responsive transcription factor protein. Comparative phenotypic analysis in near-isogenic lines revealed that fruit with netted skin had different epidermal structures from that with smooth skin including thicker cuticles, smaller, palisade-shaped epidermal and sub-epidermal cells with heavily suberized and lignified cell walls, higher peroxidase activities, which suggests multiple functions of CsSHN1 in regulating fruit skin netting and epidermal cell patterning. Among three representative cucumber inbred lines, three haplotypes at three polymorphic sites were identified inside CsSHN1: a functional copy in Gy14 (wild type) with light fruit skin netting, a copy number variant with two tandemly arrayed functional copies in WI7120 with heavy skin netting, and a loss-of-function copy in 9930 with smooth skin. The expression level of CsSHN1 in fruit exocarp of three lines was positively correlated with the skin netting intensity. Comparative analysis between cucumber and melon revealed conserved and divergent genetic mechanisms underlying fruit skin netting/reticulation that may reflect the different selection histories in the two crops. A discussion was made on genetic basis of fruit skin netting in the context of natural and artificial selections of fruit quality-related epidermal features during cucumber breeding.
果皮网纹是黄瓜（Cucumis sativus）果实的一个重要品质性状，受两个简单遗传的基因 H（网纹深）和 Rs（锈斑果皮）控制，但它们的分子基础尚不清楚。在这里，我们报道了 Rs 位点候选基因 CsSHINE1（CsSHN1）的图位克隆和功能特征，该基因编码一个含有 AP2 结构域的乙烯响应转录因子蛋白。在近等基因系中的比较表型分析表明，网纹果皮果实的表皮结构与光滑果皮果实不同，包括较厚的角质层、较小的栅栏状表皮和表皮下细胞，细胞壁强烈木质化和栓质化，过氧化物酶活性更高，这表明 CsSHN1 在调节果实果皮网纹和表皮细胞形态方面具有多种功能。在三个代表性的黄瓜自交系中，在 CsSHN1 内鉴定了三个多态性位点的三个单倍型：Gy14（野生型）中具有轻果皮网纹的功能拷贝，WI7120 中具有两个串联排列的功能拷贝的拷贝数变异体，具有光滑果皮的 9930 中则失去了功能。三个系果实外果皮中 CsSHN1 的表达水平与果皮网纹强度呈正相关。黄瓜和甜瓜之间的比较分析揭示了果皮网纹/网状结构的保守和分化的遗传机制，这可能反映了这两种作物在不同的选择历史下的差异。在黄瓜育种过程中，围绕与果实表皮特征相关的果实品质的自然和人工选择，讨论了果皮网纹的遗传基础。
