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Abstract
背景回顾：Leaf shape is considered to be one of the most significant agronomic traits in crop breeding.
提出问题：However, the molecular basis underlying leaf morphogenesis in cotton is still largely unknown.
结果1-GHCU-叶片卷曲：In this study, through genetic mapping and molecular investigation using a natural cotton mutant cu with leaves curling upward, the causal gene GHCU is successfully identified as the key regulator of leaf flattening. Knockout of GHCU or its homolog in cotton and tobacco using CRISPR results in abnormal leaf shape.
结果2-GHCU-KNGH1-生长素响应：It is further discovered that GHCU facilitates the transport of the HD protein KNOTTED1-like (KNGH1) from the adaxial to the abaxial domain. Loss of GHCU function restricts KNGH1 to the adaxial epidermal region, leading to lower auxin response levels in the adaxial boundary compared to the abaxial.
结果3-生长素响应-叶片卷曲：This spatial asymmetry in auxin distribution produces the upward-curled leaf phenotype of the cu mutant. By analysis of single-cell RNA sequencing and spatiotemporal transcriptomic data, auxin biosynthesis genes are confirmed to be expressed asymmetrically in the adaxial-abaxial epidermal cells.
结论：Overall, these findings suggest that GHCU plays a crucial role in the regulation of leaf flattening through facilitating cell-to-cell trafficking of KNGH1 and hence influencing the auxin response level.
摘 要
叶片形状被认为是作物育种中最重要的农艺性状之一。然而，有关棉花叶片形态发生的分子基础仍不清楚。本文中，通过对一个叶片向上卷曲的棉花天然突变体cu的遗传作图和分子研究，成功鉴定到GHCU基因是导致叶片压扁的关键调控因子。通过CRISPR敲除棉花和烟草中的GHCU基因或其同源基因，都会导致叶片形状异常。进一步的研究显示，GHCU能够促进HD蛋白KNGH1从近轴向远轴的转运。GHCU功能缺失会导致KNGH1蛋白被限制在近轴表皮区域，从而导致近轴边界相比于近轴具有更低水平的生长素响应。这一生长素分布的空间不对称性产生了cu突变体向上弯曲的叶片表型。通过分析单细胞测序和时空转录组数据，确认了生长素合成基因在近轴和远轴表皮细胞中存在不对称表达。综上，本文的研究结果揭示了GHCU通过介导KNGH1蛋白在细胞间的运输，从而影响生长素的响应水平，最终在叶片扁平的调控中发挥关键作用。
浙江大学胡艳教授和张天真教授为本文共同通讯作者，博后臧毅浩和已毕业研究生许晨雨为本文共同第一作者。 该研究得到了国家自然科学基金（32170328）和中国博士后科学基金（2022M712813）的联合资助。
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