Leaf shape represents a vital agronomic trait for leafy vegetables such as lettuce. Some lettuce cultivars produce lobed leaves, varying from pinnately to palmately lobed, but the genetic mechanisms remain unclear. In this study, we cloned one major quantitative trait locus (QTL) controlling palmately lobed leaves. The candidate gene, LsKN1, encodes a homeobox transcription factor, and has been shown previously to be critical for the development of leafy heads in lettuce. The LsKN1 allele that is upregulated by the insertion of a transposon promotes the development of palmately lobed leaves. We demonstrated that LsKN1 upregulated LsCUC2 and LsCUC3 through different mechanisms, and their upregulation was critical for the development of palmately lobed leaves. LsKN1 binds the promoter of LsPID to promote auxin biosynthesis, which positively contributes to the development of palmately lobed leaves. In contrast, LsKN1 suppresses GA biosynthesis to promote palmately lobed leaves. LsKN1 also binds to the promoter of LsAS1, a dorsiventrality gene, to downregulate its expression. Overexpression of the LsAS1 gene compromised the effects of the LsKN1 gene changing palmately to pinnately lobed leaves. Our study illustrated that the upregulated LsKN1 gene led to palmately lobed leaves in lettuce by integrating several downstream pathways, including auxin, gibberellin, and leaf dorsiventrality pathways.

中文翻译：

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上调的 LsKN1 基因通过生菜中的生长素、赤霉素和叶背中性途径羽状转化为掌状裂叶

叶形代表了生菜等多叶蔬菜的重要农艺性状。一些莴苣品种产生裂叶，从羽状裂片到掌状裂片不等，但遗传机制仍不清楚。在这项研究中，我们克隆了一个控制掌状裂叶的主要数量性状基因座 (QTL)。候选基因LsKN1编码同源框转录因子，之前已显示对生菜叶状茎的发育至关重要。通过插入转座子上调的LsKN1等位基因促进掌状裂叶的发育。我们证明了 LsKN1 上调LsCUC2和LsCUC3通过不同的机制，它们的上调对于掌状裂叶的发育至关重要。LsKN1 结合 LsPID 的启动子促进生长素的生物合成，这对掌状裂叶的发育有积极的贡献。相反，LsKN1 抑制 GA 生物合成以促进掌状裂叶。LsKN1 还与背侧性基因LsAS1的启动子结合，以下调其表达。LsAS1基因的过表达损害了LsKN1基因从掌状变为羽状裂叶的效果。我们的研究表明上调的LsKN1该基因通过整合多个下游途径（包括生长素、赤霉素和叶背向性途径）导致莴苣叶片呈掌状裂片状。