Distant hybridization is widely used to develop crop cultivars, whereas the hybridization process of embryo abortion often severely reduces the sought-after breeding effect. The LEAFY COTYLEDON1 (LEC1) gene has been extensively investigated as a central regulator of seed development, but it is far less studied in crop hybridization breeding. Here we investigated the function and regulation mechanism of CmLEC1 from Chrysanthemum morifolium during its seed development in chrysanthemum hybridization. CmLEC1 encodes a nucleic protein and is specifically expressed in embryos. CmLEC1’s overexpression significantly promoted the seed-setting rate of the cross, while the rate was significantly decreased in the amiR-CmLEC1 transgenic chrysanthemum. The RNA-Seq analysis of the developing hybrid embryos revealed that regulatory genes involved in seed development, namely, CmLEA (late embryogenesis abundant protein), CmOLE (oleosin), CmSSP (seed storage protein), and CmEM (embryonic protein), were upregulated in the OE (overexpressing) lines but downregulated in the amiR lines vs. wild-type lines. Future analysis demonstrated that CmLEC1 directly activated CmLEA expression and interacted with CmC3H, and this CmLEC1–CmC3H interaction could enhance the transactivation ability of CmLEC1 for the expression of CmLEA. Further, CmLEC1 was able to induce several other key genes related to embryo development. Taken together, our results show that CmLEC1 plays a positive role in the hybrid embryo development of chrysanthemum plants, which might involve activating CmLEA’s expression and interacting with CmC3H. This may be a new pathway in the LEC1 regulatory network to promote seed development, one perhaps leading to a novel strategy to not only overcome embryo abortion during crop breeding but also increase the seed yield.

中文翻译：

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转录因子CmLEC1正调控菊花杂交育种结实率

远缘杂交被广泛用于培育作物品种，而胚胎流产的杂交过程往往严重降低了受欢迎的育种效果。这多叶子叶1(LEC1) 基因作为种子发育的中心调节因子已被广泛研究，但在作物杂交育种中的研究却少得多。在这里，我们从菊花在菊花杂交种子发育过程中。CMLEC1编码一种核酸蛋白并在胚胎中特异性表达。CMLEC1的过表达显着促进了杂交的结实率，而在 amiR-CMLEC1转基因菊花。发育中的杂交胚胎的 RNA-Seq 分析揭示了参与种子发育的调控基因，即CMLEA（晚期胚胎发生丰富的蛋白质），摩尔(油质蛋白),CmSSP(种子贮藏蛋白)，和CMEM（胚胎蛋白）在 OE（过表达）系中上调，但在 amiR 系与野生型系中下调。未来的分析表明 CmLEC1 直接激活CMLEA表达并与 CmC3H 相互作用，这种 CmLEC1-CmC3H 相互作用可以增强 CmLEC1 对CMLEA. 此外，CmLEC1 能够诱导其他几个与胚胎发育相关的关键基因。综上所述，我们的研究结果表明，CmLEC1 在菊花植物的杂交胚发育中发挥着积极作用，这可能涉及激活CMLEA的表达和与 CmC3H 的相互作用。这可能是一个新的途径LEC1促进种子发育的监管网络，可能会导致一种新的策略，不仅可以克服作物育种过程中的胚胎流产，还可以提高种子产量。