Comparative transcriptome analysis of berry-sizing effects of gibberellin (GA3) on seedless Vitis vinifera L.

Abstract

Gibberellin (GA) is widely used to enlarge berries of seedless table grape and raisin varieties. The molecular mechanism underlying the berry-sizing effect of gibberelins is however poorly understood. We used a high-throughput deep sequencing technology to investigate the transcriptome and comparative expression profiles of berries from Vitis vinifera L. ‘Summer Black’ treated with GA3 with the aim of increasing the understanding of molecular mechanisms underlying the species’ expansion growth responses to exogenous GA3 hormone application. A total of 591 differentially expressed genes (DEGs) were detected including genes involved in fruit expansion and growth. There were four expansion genes, three cellulose synthase A catalytic subunit genes, four cellulose synthase-like protein genes and three xyloglucan endotransglucosylase genes. Differential expression of these genes could potentially explain the difference in the growth and sizes of fruits from control (CK) and GA3 treated (+GA) vines. In addition, the expression patterns of 14 DEGs were validated by qRT-PCR, and the outcomes agreed highly with the RNA-Seq results. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to better understand the functions of these DEGs. We also identified a large number of single nucleotide polymorphism and insertion/deletion markers, which will be a rich resource for future marker development and breeding research in grape. The transcriptome analysis provides valuable information for furthering our understanding of the molecular mechanisms that regulate the fruit expansion growth, and adds to the growing foundation for future genetic and functional genomic studies in grape fruit.