Key Laboratory of Horticultural Plant Biology, Ministry of Education, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, China.
Genome Center and Department of Plant Sciences, University of California, Davis, California, USA.
Plant Biotechnol J. 2022 Sep;20(9):1756-1769. doi: 10.1111/pbi.13861. Epub 2022 Jul 2.
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.
叶片形状是生菜等叶菜类重要的农艺性状。一些生菜品种的叶片具有裂片，从羽状到掌状裂片不等，但遗传机制尚不清楚。在这项研究中，我们克隆了一个控制掌状裂片的主要数量性状位点（QTL）。候选基因 LsKN1 编码一个同源盒转录因子，先前已被证明对生菜叶球的发育至关重要。由转座子插入上调的 LsKN1 等位基因促进掌状裂片的发育。我们证明，LsKN1 通过不同的机制上调 LsCUC2 和 LsCUC3，它们的上调对掌状裂片的发育至关重要。LsKN1 结合 LsPID 启动子促进生长素的生物合成，这对掌状裂片的发育有积极贡献。相反，LsKN1 抑制 GA 生物合成以促进掌状裂片的发育。LsKN1 还结合背腹性基因 LsAS1 的启动子来下调其表达。LsAS1 基因的过表达削弱了 LsKN1 基因从掌状到羽状裂片的作用。我们的研究表明，上调的 LsKN1 基因通过整合包括生长素、赤霉素和叶片背腹性在内的几个下游途径导致生菜叶片掌状裂片。
