Abstract
Fruit size is an important quality trait in different market classes of Cucumis sativus L., an economically important vegetable cultivated worldwide, but the genetic and molecular mechanisms that control fruit size are largely unknown. In this study, we isolated a natural cucumber mutant, short fruit 1 (sf1), caused by a single recessive Mendelian factor, from the North China-type inbred line CNS2. In addition to significantly decreased fruit length, other fruit-related phenotypic variations were also observed in sf1 compared to the wild-type (WT) phenotype, indicating that sf1 might have pleiotropic effects. Microscopic imaging showed that fruit cell size in sf1 was much larger than that in WT, suggesting that the short fruit phenotype in sf1 is caused by decreased cell number. Fine mapping revealed that sf1 was localized to a 174.3 kb region on chromosome 6. Similarly, SNP association analysis of bulked segregant RNA-Seq data showed increased SNP frequency in the same region of chromosome 6. In addition, transcriptomic analysis revealed that sf1 might control fruit length through the fine-tuning of cytokinin and auxin signalling, gibberellin biosynthesis and signal transduction in cucumber fruits. Overall, our results provide important information for further study of fruit length and other fruit-related features in cucumber.
Highlights
Cucumber (Cucumis sativus L., 2n = 14), a member of the family Cucurbitaceae, is one of the most economically important vegetable crops cultivated throughout the world
Been reported that cytokinin concentration and the expression of genes associated with cytokinin biosynthesis are maintained at high levels during early tomato fruit development, and different temporal patterns of expression of different classes of cytokinins and genes associated with their biosynthetic pathways have been observed, providing evidence for a significant role of cytokinin signalling in the cell division phase of tomato fruit development[8]
We proposed a new mechanism by which sf[1] might control fruit length in cucumber by fine-tuning cytokinin and auxin signalling and by regulating gibberellin biosynthesis and signal transduction
Summary
Wenzel et al were the first to investigate the QTLs that affect fruit quality traits in F2:3 families from a cross between the inbred lines Gyl[4] and PI432860; in their studies, three QTLs were identified and shown to be responsible for cucumber fruit length[1]. Two QTLs associated with fruit length were identified by Serquen et al in F2:3 populations developed from G421 × H-19 cucumber inbred lines[2]. Five QTLs were identified and shown to be responsible for mature fruit length in four environments using an RIL population developed from CC3 × SWCC8 cucumber inbred lines[5]. Fruit growth and development are closely associated with cell division and expansion, and cell division and expansion can be modulated by plant hormones such as cytokinins, gibberellins and auxin. We proposed a new mechanism by which sf[1] might control fruit length in cucumber by fine-tuning cytokinin and auxin signalling and by regulating gibberellin biosynthesis and signal transduction
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