Oriental melon (Cucumis melo var. acidulus) is one of the most economically important fruit crops worldwide. To elucidate the molecular basis related to soluble sugar and organic acid metabolism in the fruits of two oriental melon cultivars with different sweetness, we performed integrated metabolomic and transcriptomic analyses of the fruits of ‘Tianbao’ (A) with high sweetness and ‘Xiaocuigua’ (B) with low sweetness at different ripening stages. The high accumulation of sucrose, D-glucose, D-(+)-raffinose, and the relatively lower citric acid and malic acid might contribute to the sweet taste of A. By screening the differentially expressed genes (DEGs) and correlation analysis of the DEGs and differentially accumulated metabolites, we deduced that the B cultivar might promote the conversion of glucose and fructose into intermediate compounds for downstream processes such as glycolysis. The tricarboxylic acid (TCA) cycle might also be enhanced compared to A, thus resulting in the differential accumulation of soluble sugars and organic acids, ultimately causing the taste difference between the two oriental melon cultivars. Our finding provides important information for further exploring the metabolic mechanisms of soluble sugars and organic acids in oriental melon.

The genus Cucumis contains 52 species, including two economically significant crops, cucumber, and melon, as well as some important landraces. Cucumis melo L. 'Shengkaihua' is a widely cultivated landraces in China. It has high sugar content, early maturity, and strong genetic growth potential. Cucumis melo L. 'Shengkaihua' provides a valuable gene pool for crop improvement of Cucumis crops. In this study, the complete chloroplast (cp) genome sequence of C. melo L. 'Shengkaihua' was determined using next-generation sequencing. The entire cp genome was determined to be 156,017 bp in length. It contained large single-copy (LSC) and small single-copy (SSC) regions of 86,335 and 18,088 bp, respectively, which were separated by a pair of 25,797 bp inverted repeat (IR) regions. The genome contained 133 genes, including 88 protein-coding genes, 37 tRNA genes, and eight rRNA genes. The overall GC content of the genome is 36.9%. A phylogenetic tree reconstructed by 24 chloroplast genomes reveals that C. melo L. 'Shengkaihua' is most related to Cucumis melo var. inodorus.

2020) The complete chloroplast genome of Cucumisanguriavar.anguria (Cucurbitaceae) and its phylogenetic implication, Mitochondrial DNA Part B, 5:1, 654-655, ABSTRACTThe genus Cucumis contains 52 species, including two economically significant crops, cucumber and melon, as well as other important species. Cucumis anguria var. anguria is a wild relative of C. melon, native to Africa. Cucumis anguria is rich in vitamins and minerals in gherkin fruits and carries broadspectrum resistance to multiplex biotic and abiotic stress, such as powdery mildew, fusarium wilt, and meloidogyn incognita. Cucumis anguria provides a valuable gene pool for crop improvement of Cucumis crops. In this study, the complete chloroplast (cp) genome sequence of C. anguria was determined using next-generation sequencing. The entire cp genome was determined to be 156,577 bp in length. It contained large single-copy (LSC) and small single-copy (SSC) regions of 85,971 and 18,100 bp, respectively, which were separated by a pair of 26,253 bp inverted repeat (IR) regions. The genome contained 134 genes, including 88 protein-coding genes, 37 tRNA genes, 8 rRNA genes and 1 pseudogene infA. The overall GC content of the genome is 37.0%. A phylogenetic tree reconstructed by 48 chloroplast genomes reveals that C. anguria is a separate branch in Cucumis. ARTICLE HISTORY