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International audience; Cell fate maintenance is an integral part of plant cell differentiation and the production of functional cells, tissues, and organs. Fleshy fruit development is characterized by the accumulation of water and solutes in the enlarging cells of parenchymatous tissues. In tomato (Solanum lycopersicum), this process is associated with endoreduplication in mesocarp cells. The mechanisms that preserve this developmental program, once initiated, remain unknown. We show here that analysis of a previously identified tomato ethyl methanesulfonate-induced mutant that exhibits abnormal mesocarp cell differentiation could help elucidate determinants of fruit cell fate maintenance. We identified and validated the causal locus through mapping-by-sequencing and gene editing, respectively, and performed metabolic, cellular, and transcriptomic analyses of the mutant phenotype. The data indicate that disruption of the SlGBP1 gene, encoding GUANYLATE BINDING PROTEIN1, induces early termination of endoreduplication followed by late divisions of polyploid mesocarp cells, which consequently acquire the characteristics of young proliferative cells. This study reveals a crucial role of plant GBPs in the control of cell cycle genes, and thus, in cell fate maintenance. We propose that SlGBP1 acts as an inhibitor of cell division, a function conserved with the human hGBP-1 protein.

International audience; A forward genetic strategy, combining tomato EMS mutant variability and mapping-by-sequencing (Garcia et al., 2016; Musseau et al., 2017) allowed the identification of a DYNAMIN protein, as a key regulator of tomato fruit tissue morphology. DYNAMINs (DYNs) are large GTPase that can interact with cytoskeleton-associating proteins. In animals, DYNs are reported to be involved in cytokinesis, membrane trafficking, cytoskeletal dynamics and pathogen resistance (Konopka et al., 2006; Praefcke & Mcmahon, 2004). Plants present homologs for most dynamins found in animals, with some proven to be functional redundant. However, the role and molecular mechanisms of this particular dynamin have never been described in plants so far.In order to investigate its role in plants, experiments were conducted in both tomato and Arabidopsis thaliana models. dyn mutants share common aberrant cell size and shape, affecting pericarp cells in tomato and trichomes in Arabidopsis. Aberrant Arabidopsis trichome morphology is strikingly similar to the well described Arabidopsis mutants affected in the WAVE and ARP2/3 pathways, that are involved in actin filament nucleation (Isner et al., 2017; Sambade et al., 2014; Zimmermann et al., 2004). Our data suggest a role of this plant dynamin in actin cytoskeleton remodeling, supporting rapid cell elongation.

International audience; A forward genetic strategy, combining tomato EMS mutant variability and mapping-by-sequencing (Garcia et al., 2016; Musseau et al., 2017) allowed the identification of a DYNAMIN protein, as a key regulator of tomato fruit tissue morphology. DYNAMINs (DYNs) are large GTPase that can interact with cytoskeleton-associating proteins. In animals, DYNs are reported to be involved in cytokinesis, membrane trafficking, cytoskeletal dynamics and pathogen resistance (Konopka et al., 2006; Praefcke & Mcmahon, 2004). Plants present homologs for most dynamins found in animals, with some proven to be functional redundant. However, the role and molecular mechanisms of this particular dynamin have never been described in plants so far.In order to investigate its role in plants, experiments were conducted in both tomato and Arabidopsis thaliana models. dyn mutants share common aberrant cell size and shape, affecting pericarp cells in tomato and trichomes in Arabidopsis. Aberrant Arabidopsis trichome morphology is strikingly similar to the well described Arabidopsis mutants affected in the WAVE and ARP2/3 pathways, that are involved in actin filament nucleation (Isner et al., 2017; Sambade et al., 2014; Zimmermann et al., 2004). Our data suggest a role of this plant dynamin in actin cytoskeleton remodeling, supporting rapid cell elongation.