Assessment of the fruit-ripening-related FUL2 gene diversity in morphophysiologically contrasted cultivated and wild tomato species

Members of the Solanum section Lycopersicon are characterized by different fruit morphophysiology. The MADS-box gene FRUITFULL encodes a transcription factor involved in the regulation of flowering time and fruit development. In the present study, we identified and characterized FUL2 gene orthologs from 10 different tomato accessions in terms of polymorphism, phylogenetic relatedness, and expression pattern. The identified genes had a size from 5827 bp in S. habrochaites to 6229 bp in S. peruvianum 3966 and contained eight exons. The genes demonstrated significantly higher variability in introns (960 SNPs and 76 indels) than in exons (46 SNPs); non-synonymous SNPs were translated into 22 neutral and 20 slightly deleterious amino acid substitutions (12.24% variability in protein sequences). All predicted FUL2 proteins contained the conserved euFUL motif MPP[W/C]MLRHLNG at the C-terminus and had secondary and tertiary structures common for MADS-domain transcription factors. The FUL2-based evolutionary relationships in cultivated and wild tomatoes were mainly consistent with the accession crossability. All FUL2 genes were transcribed in flowers and fruits and demonstrated two distinct expression patterns with the maximum in mature green or ripe fruits, respectively. The obtained data should contribute to understanding of genetic potential of this ripening-related transcription factor for tomato breeding programs.