Genome-wide characterization and expression analysis of ATP-binding cassette (ABC) transporters in strawberry reveal the role of FvABCC11 in cadmium tolerance

The ATP-binding cassette (ABC) transporter is the largest gene family and is associated with the transport of various molecules, such as heavy metal ions, secondary metabolites, and phytohormones. Strawberry is an important berry fruit and a model plant for studying fleshy fruits. However, the ABC gene family has not been identified in strawberry. In present study, 115 putative ABC genes were identified in the genome of woodland strawberry (Fragaria vesca). Based on the phylogenetic analysis results, the ABC genes were grouped into eight subfamilies (6 ABCAs, 29 ABCBs, 16 ABCCs, 1 ABCDs, 2 ABCEs, 5 ABCFs, 46 ABCGs, and 10 ABCIs). Additionally, gene structure analysis revealed that the intron-exon patterns of the ABC genes are not conserved in F. vesca. Some additional conserved motifs with group specificity were found. Quantitative reverse transcription-polyrnerase chain reaction (qRT-PCR) analysis indicated ABCC subfamily gene expression across different fruit and seed developmental stages and organ profiling revealed functional diversification. Most ABCC genes exhibited preferential expression in the stems and leaves. All ABCC genes showed significant increases during the seed development stages but only ABCC8 and ABCC11 showed significant increases during fruit development. The significant changes of the 16 ABCC genes exhibited during abiotic stress treatments suggested that they might be stress-responsive genes. Over-expression of FvABCC11 in Arabidopsis partially restored seedling development under cadmium (Cd) treatment, indicated that FvABCC11 increased Cd tolerance. The results of this study provide useful information for heavy metal resistance that can be utilized to improve agricultural production.