New insights into the evolution and expression dynamics of invertase gene family in Solanum lycopersicum

Invertases catalyze the irreversible hydrolysis of sucrose into glucose and fructose and thus play key roles in carbon metabolism and plant development. To gain insights into their evolutional and functional relationships, we conducted genome-wide analyses of invertase genes in tomato and other species, focusing on their evolution and expression dynamics. The analyses unexpectedly identified in the tomato genome 5 pseudo invertsase sequences and 5 non-functional cell wall invertases (CWINs) lacking the critical beta-fructosidase motif or other amino acids required for hydrolyzing sucrose. Based on their phylogeny relationship and exon-intron structure, we speculated that the invertase gene family could arose from different ancestral genes. The acid invertase gene family, comprised of CWIN and vacuolar invertase (VIN), expanded through segmental and tandem duplication. Analysis of functional divergence suggests site-specific shifted evolutionary rate (Type-I) have played an important role in evolutionary novelties after acid invertase gene duplication in plants. Finally, paralogs within each of the CWIN, VIN and CIN subfamilies exhibited diverse expression responses to the same set of stress treatments including salt and temperature stresses, probably reflecting functional adaptability of the invertase genes during evolution.