Solanum lycopersicum CLASS-II KNOX genes regulate fruit anatomy via gibberellin-dependent and independent pathways.

This article investigates the role of CLASS-II KNOX (TKN-II) genes in regulating fruit anatomy in tomato (Solanum lycopersicum), focusing on their influence on pericarp development through gibberellin (GA)-dependent and independent pathways. Using a transgenic line with mRNA knockdown of TKN-II genes (35S: amiR-TKN-II), the study found that reduced TKN-II expression leads to fewer pericarp cell layers, smaller pericarp cell sizes, and altered fruit shape, with an increased number of cells around the fruit equator. While the procera (pro) mutant, which constitutively activates GA response, can override the fruit shape and pericarp layer number phenotypes caused by TKN-II knockdown, it does not fully rescue the reduced pericarp width and cell size, indicating that TKN-II genes regulate fruit shape via GA signaling but control pericarp cell size through additional GA-independent mechanisms. Furthermore, exogenous application of GA3 increased pericarp width in both wild-type and knockdown fruits but did not eliminate the differences caused by TKN-II suppression. These findings suggest that TKN-II genes coordinate tomato fruit morphology by integrating hormonal and developmental signals through multiple pathways.