Du Fei, Mo Yajin, Israeli Alon, Wang Qingqing, Yifhar Tamar, Ori Naomi, Jiao Yuling
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Plant J. 2020 Nov;104(4):1073-1087. doi: 10.1111/tpj.14982. Epub 2020 Sep 25.
Compound leaves are composed of multiple separate blade units termed leaflets. In tomato (Solanum lycopersicum) compound leaves, auxin promotes both leaflet initiation and blade expansion. However, it is unclear how these two developmental processes interact. With highly variable complexity, tomato compound leaves provide an ideal system to address this question. In this study, we obtained and analyzed mutants of the WUSCHEL-RELATED HOMEOBOX (WOX) family gene SlLAM1 from tomato, whose orthologs in tobacco (Nicotiana sylvestris) and other species are indispensable for blade expansion. We show that SlLAM1 is expressed in the middle and marginal domains of leaves, and is required for blade expansion in leaflets. We demonstrate that sllam1 mutants cause a delay of leaflet initiation and slightly alter the arrangement of first-order leaflets, whereas the overall leaflet number is comparable to that of wild-type leaves. Analysis of the genetic interactions between SlLAM1 and key auxin signaling components revealed an epistatic effect of SlLAM1 in determining the final leaf form. Finally, we show that SlLAM1 is also required for floral organ growth and affects the fertility of gametophytes. Our data suggest that SlLAM1 promotes blade expansion in multiple leaf types, and leaflet initiation can be largely uncoupled from blade expansion during compound leaf morphogenesis.
复叶由多个称为小叶的独立叶片单元组成。在番茄（Solanum lycopersicum）复叶中，生长素促进小叶起始和叶片扩展。然而，尚不清楚这两个发育过程是如何相互作用的。番茄复叶具有高度可变的复杂性，为解决这个问题提供了一个理想的系统。在本研究中，我们从番茄中获得并分析了WUSCHEL相关同源框（WOX）家族基因SlLAM1的突变体，其在烟草（Nicotiana sylvestris）和其他物种中的直系同源基因对叶片扩展是不可或缺的。我们发现SlLAM1在叶片的中部和边缘区域表达，并且是小叶叶片扩展所必需的。我们证明sllam1突变体导致小叶起始延迟，并略微改变一级小叶的排列，而小叶总数与野生型叶片相当。对SlLAM1与关键生长素信号成分之间遗传相互作用的分析揭示了SlLAM1在决定最终叶片形态方面的上位效应。最后，我们表明SlLAM1对花器官生长也是必需的，并影响配子体的育性。我们的数据表明，SlLAM1促进多种叶型的叶片扩展，并且在复叶形态发生过程中，小叶起始在很大程度上可以与叶片扩展解偶联。
