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Heat stress, as a negative factor, severely threatens the quality and production of bottle gourd, which prefers to grow in a warm environment. To understand which genes are involved in the resistance to heat stress in bottle gourd (Lagenaria siceraria (Mol.) Standl.), we analyzed the characteristics of two genetic bottle gourd varieties, "Mei feng"-MF (heat resistant) and "Lv long"-LL (heat sensitive). Under heat stress, MF plants exhibited a higher survival rate, lower relative electrolytic leakage, and decreased stomatal aperture compared with LL. In addition, RNA-Seq was carried out on the two varieties under normal conditions and heat stress. The results revealed a total of 1485 up-regulated and 946 down-regulated genes under normal conditions, while 602 genes were up-regulated and 1212 genes were down-regulated under heat stress. Among these genes, several differentially expressed genes (DEGs) involved in the MAPK (mitogen-activated protein kinase) signaling pathway and members of bHLH (basic helix-loop-helix) transcription factors showed significant up- or down-regulation after heat stress. Next, to validate these findings, we conducted quantitative real-time PCR (qRT-PCR) analysis, which confirmed the expression patterns of the genes detected through RNA-Seq. Collectively, the DEGs between the two contrasting cultivars identified in our study provide novel insight into excavating helpful candidate genes associated with heat tolerance in bottle gourd. [ABSTRACT FROM AUTHOR]

Cucumber (Cucumis sativus L.) is an important vegetable crop, which is thermophilic not heat resistant. High-temperature stress always results in sterility at reproductive stage. In the present study, we evaluate the male flower developmental changes under normal (CK) and heat stress (HS) condition. After HS, the activities of peroxidase (POD) and superoxide dismutase (SOD) and the contents of malondialdehyde (MDA) were increased. In addition, the pollen fertility was significantly decreased; and abnormal tapetum and microspore were observed by paraffin section. Transcriptome analysis results presented that total of 5828 differentially expressed genes (DEGs) were identified after HS. Among these DEGs, 20 DEGs were found at four stages, including DNA binding transcription factor, glycosyltransferase, and wound-responsive family protein. The gene ontology term of carbohydrate metabolic process was significantly enriched in all anther stages, and many saccharides and starch synthase-related genes, such as invertase, sucrose synthase, and starch branching enzyme, were significantly different expressed in HS compared with CK. Furthermore, co-expression network analysis showed a module (midnightblue) strongly consistent with HS, and two hub genes (CsaV3_6G004180 and CsaV3_5G034860) were found with a high degree of connectivity to other genes. Our results provide comprehensive understandings on male flower development in cucumber under HS. [ABSTRACT FROM AUTHOR]

Abstract This study aims to investigate key genes involved in molecular regulatory networks of cucumber sex determination. Genome-wide high-throughput RNA sequencing was performed for young apical buds of gynoecious and weak female cucumber at three growth stages (one-leaf one-bud, three-leaf one-bud, and five-leaf one-bud). Seven comparisons from the same cultivar at three different stages and at the same stage between the two cultivars were analyzed, and the results revealed that compared with differentially expressed genes (DEGs) in weak female cucumber, more genes were upregulated at the one-leaf one-bud stage and downregulated at the three-leaf one-bud stage in gynoecious cucumber. In addition, there were four kinds of gene expression trends (0, 1, 6, and 7), which were significantly enriched in gynoecious cucumber, while only two kinds of gene expression trends (5 and 6) were significantly enriched in weak female cucumber. Together with the data of the Gene Ontology (GO), pathway, gene expression trends and qRT-PCR, nine genes were identified and considered as candidate genes that may be involved in sex differentiation regulation in cucumber. These genes included Cs-MCM6 , Cs-ACT3 , Cs-XRCC4 , Cs-MCM2 , Cs-CDC45 , Cs-Dpri , Cs-H2B , Cs-CDC20 and Cs-CNGC1. Among these genes, five genes (Cs-MCM6 , Cs-MCM2 , Cs-CDC45 , Cs-Dpri , and Cs-CDC20) were involved in the cell cycle pathway, suggesting that the cell cycle pathway may play an important role in sex determination in cucumber. Highlights • RNA-Seq of gynoecious and weak female cucumber at three different growth stages. • The comprehensive analysis of GO, KEGG gene expression trends and qRT-PCR. • Among Nine genes identified as candidates, five involved in the cell cycle pathway. • The analysis of probable connections between the cell cycle genes and ET related genes. • A probable model of sex differentiation regulation network was built. [ABSTRACT FROM AUTHOR]

Temperature rising caused by global warming has imposed significant negative effects on crop qualities and yields. To get the well-known molecular mechanism upon the higher temperature, we carefully analyzed the RNA sequencing-based transcriptomic responses of two contrasting chieh-qua genotypes: A39 (heat-tolerant) and H5 (heat-sensitive). In this study, twelve cDNA libraries generated from A39 and H5 were performed with a transcriptome assay under normal and heat stress conditions, respectively. A total of 8705 differentially expressed genes (DEGs) were detected under normal conditions (3676 up-regulated and 5029 down-regulated) and 1505 genes under heat stress (914 up-regulated and 591 down-regulated), respectively. A significant positive correlation between RNA-Seq data and qRT-PCR results was identified. DEGs related to heat shock proteins (HSPs), ubiquitin-protein ligase, transcriptional factors, and pentatricopeptide repeat-containing proteins were significantly changed after heat stress. Several genes, which encoded HSPs (CL2311.Contig3 and CL6612.Contig2), cytochrome P450 (CL4517.Contig4 and CL683.Contig7), and bHLH TFs (CL914.Contig2 and CL8321.Contig1) were specifically induced after four days of heat stress. DEGs detected in our study between these two contrasting cultivars would provide a novel basis for isolating useful candidate genes of heat stress responses in chieh-qua. [ABSTRACT FROM AUTHOR]

Drought stress is one of the most serious threats to cucumber quality and yield. To gain a good understanding of the molecular mechanism upon water deficiency, we compared and analyzed the RNA sequencing-based transcriptomic responses of two contrasting cucumber genotypes, L-9 (drought-tolerant) and A-16 (drought-sensitive). In our present study, combining the analysis of phenotype, twelve samples of cucumber were carried out a transcriptomic profile by RNA-Seq under normal and water-deficiency conditions, respectively. A total of 1008 transcripts were differentially expressed under normal conditions (466 up-regulated and 542 down-regulated) and 2265 transcripts under drought stress (979 up-regulated and 1286 down-regulated). The significant positive correlation between RNA sequencing data and a qRT-PCR analysis supported the results found. Differentially expressed genes (DEGs) involved in metabolic pathway and biosynthesis of secondary metabolism were significantly changed after drought stress. Several genes, which were related to sucrose biosynthesis (Csa3G784370 and Csa3G149890) and abscisic acid (ABA) signal transduction (Csa4M361820 and Csa6M382950), were specifically induced after 4 days of drought stress. DEGs between the two contrasting cultivars identified in our study provide a novel insight into isolating helpful candidate genes for drought tolerance in cucumber. [ABSTRACT FROM AUTHOR]

• Low light stress induced hypocotyl elongation in cucumber. • The candidate region of hypocotyl elongation under low light was mapped on Chr 2 by BSA-seq. • Low light regulate the expression of auxin related genes. Cucumber (Cucumis sativus L.) is cultivated worldwide and is known to be photophilic and thermophilic. Low light stress (LLS) in winter and spring in Northern and early spring in Southern China has a severe impact on the growth and development of greenhouse cucumbers. However, the molecular regulatory mechanisms of LLS in cucumbers remain unclear, which seriously limits the development of cucumber breeding under LLS. In this study, we investigated hypocotyl differences in two cucumber lines grown under LLS and normal (CK) condition. Under LLS, the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and malondialdehyde (MDA) declined tovarying degrees compared with CK, and Y8 showed a relatively small decline. The hypocotyl length of the F 2 population is a quantitative trait controlled by multiple genes under LLS conditions. The candidate region for hypocotyl elongation under LLS was mapped to chromosome 2 using bulk segregant analysis sequencing (BSA-seq). In addition, transcriptome analysis revealed 2786 differentially expressed genes (DEGs), of which 871 DEGs were specifically identified between Y5 and Y8 under LLS. Among these DEGs, 12 DEGs were involved in plant hormone signal transduction. Association analysis of the BSA-Seq and RNA-Seq results suggested that 36 DEGs were as candidate genes. Furthermore, three TFs (NAC, MYB and C2H2) may be considered the most likely candidate genes of hypocotyl elongation under LLS. Our results provide comprehensive understandings of the mechanism of hypocotyl elongation under LLS, and contribute to foundation for cloning the genes involved in hypocotyl elongation under LLS. [ABSTRACT FROM AUTHOR]