QTL-seq Analysis of Seed Size Trait in Grape Provides New Molecular Insight on Seedlessness

Abstract

Background Seedlessness in grape ( Vitis vinifera ) is an important commercial trait for both the fresh and drying markets. However, despite numerous studies, the mechanisms and key genes regulating grape seedlessness are mostly unknown. Results In this study, we sequenced the genomes of the V. vinifera seeded cultivar ‘Red Globe’, the seedless cultivar ‘Centennial’, as well as the derived hybrids. Nonsynonymous SNPs were identified and analyzed with respect to published transcriptome data. All the DEGs containing nonsynonymous SNPs were further analyzed in terms of expression patterns, Gene Ontology and pathway enrichment. A potential QTL region associated with seed size was characterized based on SNP indices for both seedless and seeded progeny. Expression analysis of candidate genes during ovule development in multiple seeded and seedless grape cultivars further indicates their potential function in grape seed development. Conclusion In summary, DEGs containing nonsynonymous SNPs were mainly protein kinase, transcription factors, cytochrome P450 and other factors related to seed development, which were mainly involved in biological processes like hormone balance, seed coat and endosperm development, reproductive organ development, oxidation and reduction, senescence and cell death. Based on SNP-index and expression pattern analysis, three genes were further identified as potential seedlessness-related genes. Overall the data cast light on the differences of seed development between seeded and sedless progeny in perspective of both functional variants and expression pattern,which provides valuable candidates for future functional study.