SummaryPlant organ size and shape are major agronomic traits that depend on cell division and expansion, which are both regulated by complex gene networks. In several eudicot species belonging to the rosid clade, organ growth is controlled by a repressor complex consisting of PEAPOD (PPD) and KINASE-INDUCIBLE DOMAIN INTERACTING (KIX) proteins. Whether the function of these proteins as regulators of organ size is conserved in asterids as well, which together with the rosids constitute most of the core eudicot species, is still unknown. We used CRISPR-Cas9 genome editing to target SlKIX8 and SlKIX9 in the asterid model species tomato (Solanum lycopersicum) and analyzed loss-of-function phenotypes. We found that loss of function of SlKIX8 and SlKIX9 led to the production of enlarged, dome-shaped leaves and that these leaves exhibited increased expression of putative SlPPD target genes. Moreover, kix8 kix9 mutants carried bigger fruits with increased pericarp thickness. Protein interaction assays also confirmed that SlKIX8 and SlKIX9 act as molecular bridges between the SlPPD and SlTOPLESS co-repressor proteins. Our results show that KIX8 and KIX9 are conserved regulators of organ size in distinct eudicot species and can thus provide strategies to improve yield in fruit crops.
Control of Plant Organ Size by KLUH/CYP78A5-Dependent Intercellular Signaling
