The WOX family transcriptional regulator SlLAM1 controls compound leaf and floral organ development in Solanum lycopersicum
Abstract Plant specific WOX family transcription factors play important roles from embryogenesis to lateral organ development. The WOX1 transcription factors, belonging to the modern clade of WOX family, are found to regulate leaf blade outgrowth specifically in the mediolateral axis. However, the role of WOX1 in compound leaf development is still unknown. Phylogenetic analysis of the whole WOX family in tomato indicates that there are 10 members that represent the modern, intermediate, and ancient clades. Using phylogenetic analysis and a reverse genetic approach, we identified the modern clade SlLAM1 gene from tomato and analyzed its function and tissue specific expression pattern. Here, we show that knocking out SlLAM1 via CRISPR/Cas9-mediated genome editing led to narrow leaves, and reduced number of secondary leaflets. Overexpression of tomato SlLAM1 could rescue the defect of tobacco lam1 mutant. Anatomical and transcriptomic analyses demonstrated that floral organ development, fruit size, secondary leaflet initiation, and leaf complexity were altered due to loss-of-function of SlLAM1. These findings elucidate that tomato SlLAM1 plays an important role in the regulation of secondary leaflet initiation, in addition to its conserved function in blade expansion.
