Cucurbitacin and volatile compound profiling reveals independent domestication of cucumber (Cucumis sativus L.) fruit.

Profiling of metabolites that confer bitter taste and flavor to cucumber products is necessary to produce preferred products. In this study, cucurbitacins A, B, C, D, E, and I and untargeted volatile compounds were analyzed using the fruit of 69 inbred cucumber of diverse cultivars. Only cucurbitacin C was detected in six inbreds. They were classified into four clusters based on the profiles of cucurbitacins and volatile compounds. Clusters 2 and 3 showed the largest difference with the highest and lowest volatile contents, respectively. Clusters 1 and 4 showed different fruit phenotypes of length and color. Fifteen F1 hybrids from selected inbreds were analyzed. Total volatile compound (TVC) content, especially for the alcohol content, was lower in the F1 hybrids than the mid-parent values, and the ratio of aldehyde to TVC was increased. This profiling will contribute to produce cucumber products with no bitter taste and improved flavor.

Expanded transcriptomic view of strawberry fruit ripening through meta-analysis.

Strawberry is an important fruit crop and a model for studying non-climacteric fruit ripening. Fruit ripening and senescence influence strawberry fruit quality and postharvest storability, and have been intensively studied. However, genetic and physiological differences among cultivars preclude consensus understanding of these processes. We therefore performed a meta-analysis by mapping existing transcriptome data to the newly published and improved strawberry reference genome and extracted meta-differentially expressed genes (meta-DEGs) from six cultivars to provide an expanded transcriptomic view of strawberry ripening. We identified cultivar-specific transcriptome changes in anthocyanin biosynthesis-related genes and common changes in cell wall degradation, chlorophyll degradation, and starch metabolism-related genes during ripening. We also identified 483 meta-DEGs enriched in gene ontology categories related to photosynthesis and amino acid and fatty acid biosynthesis that had not been revealed in previous studies. We conclude that meta-analysis of existing transcriptome studies can effectively address fundamental questions in plant sciences.

Transcriptome Analysis of the Fruit of Two Strawberry Cultivars "Sunnyberry" and "Kingsberry" That Show Different Susceptibility to Botrytis cinerea after Harvest.

Gray mold (Botrytis cinerea) is a fungal plant pathogen causing postharvest decay in strawberry fruit. Here, we conducted a comparative transcriptome analysis to identify differences in gene expression between the immature-green (IG) and mature-red (MR) stages of the "Sunnyberry" (gray mold-resistant) and "Kingsberry" (gray mold susceptible) strawberry cultivars. Most of the genes involved in lignin and alkane-type wax biosynthesis were relatively upregulated in "Sunnyberry". However, pathogenesis-related proteins encoding R- and antioxidant-related genes were comparatively upregulated in "Kingsberry". Analysis of gene expression and physiological traits in the presence and absence of B. cinerea inoculation revealed that the defense response patterns significantly differed between IG and MR rather than the cultivars. "Kingsberry" showed higher antioxidant induction at IG and upregulated hemicellulose-strengthening and R genes at MR. Hence, "Sunnyberry" and "Kingsberry" differed mainly in terms of the expression levels of the genes forming cuticle, wax, and lignin and controlling the defense responses. These discrepancies might explain the relative difference between these strawberry cultivars in terms of their postharvest responses to B. cinerea.

Comparative transcriptome and metabolome analyses of two strawberry cultivars with different storability.

Postharvest storability is an important trait for breeding strawberry (Fragaria × ananassa Duch.). We evaluated the postharvest fruit quality of five strawberry cultivars ('Durihyang', 'Kingsberry', 'Maehyang', 'Seolhyang', and 'Sunnyberry') and identified differences in their fruit ripening during the transition from the big-green to fully-red stage between two cultivars with the highest ('Sunnyberry') and lowest ('Kingsberry') storability, using comparative transcriptome and -metabolome analysis. The differentially expressed genes revealed transcriptome changes related to anthocyanin biosynthesis and cell walls. Consistently, the metabolites of both cultivars showed general changes during ripening along with cultivar-specific characteristics in sugar and amino acid profiles. To identify the genes responsible for storability differences, we surveyed the expression of transcription factors, and found that the expression levels of WRKY31, WRKY70, and NAC83 correlated with delayed senescence and increased storability. Among them, the expression levels of NAC83, and its downstream target genes, in the five cultivars suggested that NAC83 expression can be used to predict postharvest strawberry fruit storability.