Alfalfa (Medicago sativa L.) is a perennial legume extensively planted throughout the world as a high nutritive value livestock forage. Flowering time is an important agronomic trait that contributes to the production of alfalfa hay and seeds. However, the underlying molecular mechanisms of flowering time regulation in alfalfa are not well understood. In this study, an early-flowering alfalfa genotype 80 and a late-flowering alfalfa genotype 195 were characterized for the flowering phenotype. Our analysis revealed that the lower jasmonate (JA) content in new leaves and the downregulation of JA biosynthetic genes (i.e. lipoxygenase, the 12-oxophytodienoate reductase-like protein, and salicylic acid carboxyl methyltransferase) may play essential roles in the early-flowering phenotype of genotype 80. Further research indicated that genes encode pathogenesis-related proteins [e.g. leucine rich repeat (LRR) family proteins, receptor-like proteins, and toll-interleukin-like receptor (TIR)-nucleotide-binding site (NBS)-LRR class proteins] and members of the signaling receptor kinase family [LRR proteins, kinases domain of unknown function 26 (DUF26) and wheat leucine-rich repeat receptor-like kinase10 (LRK10)-like kinases] are related to early flowering in alfalfa. Additionally, those involved in secondary metabolism (2-oxoglutarate/Fe (II)-dependent dioxygenases and UDP-glycosyltransferase) and the proteasome degradation pathway [really interesting new gene (RING)/U-box superfamily proteins and F-box family proteins] are also related to early flowering in alfalfa. Integrated phenotypical, physiological, and transcriptomic analyses demonstrate that hormone biosynthesis and signaling pathways, pathogenesis-related genes, signaling receptor kinase family genes, secondary metabolism genes, and proteasome degradation pathway genes are responsible for the early flowering phenotype in alfalfa. This will provide new insights into future studies of flowering time in alfalfa and inform genetic improvement strategies for optimizing this important trait.

中文翻译：

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通过转录组分析鉴定和表征参与紫花苜蓿（Medicago sativa L.）新叶早期开花的调控途径

紫花苜蓿（Medicago sativa L.）是一种多年生豆科植物，作为一种高营养价值的牲畜饲料在世界各地广泛种植。开花时间是一个重要的农艺性状，有助于生产苜蓿干草和种子。然而，苜蓿开花时间调控的潜在分子机制尚不清楚。在这项研究中，早花苜蓿基因型 80 和晚花苜蓿基因型 195 被表征为开花表型。我们的分析表明，新叶中茉莉酸 (JA) 含量较低和 JA 生物合成基因（即脂氧合酶、12-氧代植物二烯酸还原酶样蛋白和水杨酸羧基甲基转移酶）的下调可能在早花表型中起重要作用基因型 80。进一步的研究表明，基因编码与发病机制相关的蛋白质 [例如富含亮氨酸重复序列 (LRR) 家族蛋白质、受体样蛋白质和 Toll-白介素样受体 (TIR)-核苷酸结合位点 (NBS)-LRR 类蛋白质] 和信号受体激酶家族的成员 [LRR 蛋白、未知功能的激酶结构域 26 (DUF26) 和小麦富含亮氨酸重复受体样激酶 10 (LRK10) 样激酶] 与苜蓿的早期开花有关。此外，参与次级代谢（2-酮戊二酸/铁（II）依赖性双加氧酶和UDP-糖基转移酶）和蛋白酶体降解途径的那些[非常有趣的新基因（RING）/U-box超家族蛋白和F-box家族蛋白]也与苜蓿早花有关。综合表型、生理、转录组学分析表明，激素生物合成和信号通路、发病相关基因、信号受体激酶家族基因、次级代谢基因和蛋白酶体降解通路基因是造成苜蓿早期开花表型的原因。这将为紫花苜蓿开花时间的未来研究提供新的见解，并为优化这一重要性状的遗传改良策略提供信息。