The FPF Gene Family in Tomato: Genome-Wide Identification and the Role of SlFPF1 in Gibberellin-Dependent Growth

Flowering promoting factor 1 (FPF1) is a key regulator of plant flowering time. While the functions of the FPF family have been characterized in species such as Arabidopsis and rice, systematic studies on the tomato FPF family remain limited. In this study, we comprehensively analyzed the FPF family in tomato (Solanum lycopersicum L.), identifying five SlFPF members in the tomato genome. Phylogenetic analysis classified these genes into five distinct subgroups, and chromosome mapping revealed their distribution across three chromosomes, with the highest density on chromosome 1. Promoter analysis identified a range of putative cis-acting elements related to abiotic stress and hormonal responses. Differential expression analysis of various tissues showed that the five SlFPF genes exhibit varying expression levels, where SlFPF1 had a significantly higher expression compared to the others. Following treatments with abiotic stresses (NaCl, PEG, dark, and low light) and phytohormones (GA, MeJA, ABA, and SA), SlFPF1 expression is notably higher under GA treatment than under other conditions. Based on these findings, SlFPF1 and GA treatments were selected for further functional analysis. The results show that GA treatment significantly promotes multiple morphological traits, including root length, stem diameter, leaf area, plant height, dry weight, and fresh weight. However, silencing SlFPF1 expression led to a reduction in all these traits. Moreover, in SlFPF1-silenced plants, GA treatment failed to enhance root length, leaf area, fresh weight, and dry weight, indicating that GA-dependent growth promotion in tomato plants relies on SlFPF1. This study provides a theoretical foundation for understanding the SlFPF gene family and its role in plant growth and stress responses.