The zinc finger transcription factor SlZFP2 regulates locular tissue morphogenesis

In tomato (Solanum lycopersicum L.) fruit, locular tissue (LT) is a unique jelly-like structure that differentiates from the central axis of the fruit following ovule fertilization. LT is essential for seed development and dispersal, preventing early germination, and initiating fruit ripening. In this work, we studied a “gel-less” mutant and identified the underlying mutation in the coding sequence of the C2H2 zinc finger transcription factor (TF) SlZFP2. Histological, cytological and molecular characterization of zfp2-CRISPR/Cas9 knockout lines revealed an early and strong impact of zfp2 disruption on cell division and endoreduplication in LT. Further, model-based analysis of cellular data revealed that the cell division was the main altered process explaining the zfp2 mutant phenotype. RNA-seq analysis of young LT further highlighted global transcriptional changes of cell cycle-related genes between WT and zfp2 mutants, providing insight into the molecular players involved in locular tissue differentiation. This multi-faceted approach uncovers SlZFP2 as a regulator of LT morphogenesis and reveals its main action in regulating cell division. Since few regulators of LT developmental processes have been described so far, this work on SlZFP2 establishes groundwork for future studies aimed at deciphering the complex regulatory networks governing fruit tissue development.