Compound leaves are composed of multiple separate blade units termed leaflets. In tomato 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.
A research team led by Prof. GAO Caixia at Institute of Genetics and Developmental Biology of Chinese Academy of Sciences obtained and analyzed mutants of the WUSCHEL-RELATED HOMEOBOX (WOX) family gene SlLAM1 from tomato, whose orthologs in tobacco and other species are indispensable for blade expansion. Researchers show that SlLAM1 is expressed in the middle and marginal domains of leaves, and is required for blade expansion in leaflets; sllam1mutants cause a delay of leaflet initiation and slightly alter the arrangement of first-order leaflets, whereas the overall leaflet number is comparable to 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. 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.
The study was published in The Plant Journal (doi:10.1111/tpj.14982). Undergraduate student MO Yajin at University of Chinese Academy of Sciences and post-doctoral fellow DU Fei in Prof. JIAO’s team contributed equally to the study. Prof. JIAO is a doctoral supervisor at University of Chinese Academy of Sciences.
