Genome-wide analysis of the invertase genes in strawberry (Fragaria×ananassa)

Sugar is an important material basis in fruit development, and strawberry fruit flavour and sweetness largely depend on the sugar content and variety. Invertases (INVs) play an important role in the regulation of sugar accumulation because they irreversibly catalyse the hydrolysis of sucrose into the corresponding nucleoside diphosphate-glucose, glucose or fructose in fruit. In this work, we provided a comprehensive analysis of the INV gene family in octoploid strawberry (Fragaria×ananassa), including the gene structure, chromosomal locations, conserved domains, and gene evolution and expression profiles during strawberry fruit development. Our study revealed that polyploid events resulted in the abundant amplification (almost three- or four-fold) of the INV gene in the F.×ananassa genome, and these amplified INV genes showed dominant expression in strawberry fruit. More than half of the FaINVs transcripts with low expression had incomplete coding sequences by alternative splicing. Previous studies have shown that cell wall invertases (CWINV) are involved in the regulation of phloem unloading and sink strength establishment. The expression of FaCWINV1 was markedly upregulated during fruit development and strongly expressed in ripe fruit. Moreover, a significant correlation was observed between the total sugar content and the FaCWINV1 expression level. These findings suggest that FaCWINV1 may be involved in sugar accumulation in strawberry fruit. Taken together, the results of our study will be beneficial for further research into the functions of INVs in the regulation of fruit ripening.