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.
MO Yajin, an undergraduate at university of Chinese Academy of Sciences, worked together with the research team led by Prof. JIAO Yuling at the Institute of Genetics and Developmental Biology, CAS, to answer the question. The research is recently published in The Plant Journal (doi:10.1111/tpj.14982 ), MO Yajin and DU Fei (a post doctor of Prof. JIAO’s team) are the first authors.
In their study, mutants of theWUSCHEL-RELATED HOMEOBOX (WOX) family geneSlLAM1from tomato are obtained and analyzed, whose orthologs in tobacco and other species are indispensable for blade expansion. The study shows thatSlLAM1is expressed in the middle and marginal domains of leaves, and is required for blade expansion in leaflets, and demonstrates thatsllam1mutants 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 betweenSlLAM1 and key auxin signaling components revealed an epistatic effect ofSlLAM1in determining the final leaf form. The study also shows thatSlLAM1 is also required for floral organ growth and affects the fertility of gametophytes, SlLAM1promotes blade expansion in multiple leaf types, and leaflet initiation can be largely uncoupled from blade expansion during compound leaf morphogenesis.
