The cultivation and production of cucumber are seriously affected by downy mildew caused by Pseudoperonospora cubensis. Downy mildew damages leaves, stems and inflorescences, and then reduces the yield and quality of cucumber. This review summarized the research advances in cucumber downy mildew, including pathogen detection and defense pathways, regulatory factors, mining of pathogens-resistant candidate genes, proteomic and genomic analysis, and development of QTL remarks. This review may facilitate clarifying the resistance mechanisms of cucumber to downy mildew.
Cucumis sativus/genetics* ; Oomycetes/genetics* ; Peronospora ; Plant Diseases/genetics* ; Proteomics

Cucumber (Cucumis sativus) is an important vegetable crop in the world. Agrobacterium-mediated transgenic technology is an important way to study plant gene functions and improve varieties. In order to further accelerate the transgenic research and breeding process of cucumber, we described the progress and problems of Agrobacterium tumefaciens-mediated transgenic cucumber, from the influencing factors of cucumber regeneration ability, genetic transformation conditions and various additives in the process. We prospected for improving the genetic transformation efficiency and safety selection markers of cucumber, and hoped to provide reference for the research of cucumber resistance breeding and quality improvement.
Agrobacterium tumefaciens ; metabolism ; Breeding ; Cucumis sativus ; genetics ; microbiology ; Plants, Genetically Modified ; microbiology ; Research ; Transformation, Genetic

Hairy roots of Cucumis sativus L. could be incited directly from the cut edges of 10-day-old cotyledon explants after infection with the strain Agrobacterium rhizogenes ATCC15834 harboring agropine-type plasmid, pRiA4b for 5 days. It was observed that the percentage of rooting cotyledon explants was more than 90 % 10 days after infection. Hairy roots could grow rapidly and highly branched on solid plant growth regulator-free MS medium. The PCR amplification of rol B genes and vir C gene showed that T-DNA of Ri plasmid of A. rhizogenes was integrated and expressed into the genome of transformed cucumber hairy roots. A bacterium-free transformed cucumber hairy root line was selected to culture on solid MS medium to examine influence of exogenous cytokinin 6-BA on growth and morphology alteration of cucumber hairy roots. The results showed that cytokinin 6-BA can influence the growth and altered the morphology of hairy roots. With increasing of 6-BA concentrations, Cucumber hairy roots become shorter and thicker and less branched. 6-BA at the concentration of 0.1 to approximately 3.0 mg/L could delay the appearance of maximum growth peak by 5 days and decreased the content of soluble protein, enhanced the activities of SOD and POD and decreased the levels of endogenous ethylene evolution in cucumber hairy roots. Our results also indicated that cytokinin 6-BA in the medium could influence growth and morphology alternation of cucumber hairy roots and delay its senescence of hairy roots by acting through ethylene.
Cucumis sativus ; genetics ; growth & development ; Culture Media ; Culture Techniques ; Cytokinins ; pharmacology ; Plant Growth Regulators ; pharmacology ; Plant Roots ; genetics ; growth & development ; Rhizobium ; genetics ; Transfection ; Transformation, Genetic

Soil archaea and fungi play important roles in the greenhouse soil ecosystem. To develop and apply rich microbial resources in greenhouse ecological environment, and to understand the interaction between microbes and plants, we constructed archaeal 16S rRNA and fungal 18S rRNA gene libraries to analyze the compositions of archaeal and fungal communities. Total greenhouse soil DNA was directly extracted and purified by skiving-thawing-lysozyme-proteinase K-SDS hot treatment and treatment of cetyltriethylammnonium bromide (CTAB). After PCR amplification, retrieving, ligating, transforming, screening of white clones, archaeal 16S rRNA and fungal 18S rRNA gene libraries were constructed. The sequences of archaea and fungi were defined into operational taxonomic units (OTUs) when 97% similarity threshold for OTU assignment was performed by using the software DOTUR. Phylogenetic analysis showed that crenarchaeota and unidentified-archaea were the two major sub-groups and only a few of euryarchaeota existed in the archaeal clone library, total 45 OTUs. All the crenarchaeota belonged to thermoprotei; except for Basidiomycotina, the other four sub-group fungi were discovered in the fungal library, total 24 OTUs. The diversities of archaea were very abundant and a few euryarchaeota (methanebacteria) existed in the archaeal clone library, it might be directly related to the long-term high temperature, high humidity, and high content of organic matter. The limitation of oxygen was the other reason for causing this phenomenon; Ascomycotina (over 80%) was the dominant sub-groups in fungal library. It was because most of the plant fungal diseases belonged to soil-borne diseases which gone through the winter by the ways of scierotium or perithecium and became the sources of primary infection.
Archaea ; genetics ; growth & development ; Biodiversity ; Cloning, Molecular ; Cucumis sativus ; growth & development ; Fungi ; genetics ; growth & development ; Gene Library ; Genes, rRNA ; Microclimate ; Phylogeny ; Plant Roots ; microbiology ; RNA, Archaeal ; genetics ; RNA, Fungal ; genetics ; RNA, Ribosomal, 16S ; genetics ; RNA, Ribosomal, 18S ; genetics ; Soil Microbiology

The replicase genes of five isolates of Cucumber green mottle mosaic virus from Jiangsu, Zhejiang, Hunan and Beijing were amplificated, sequenced and analyzed. The similarities of nucleotide acid sequences indicated that 129 kD and 57 kD replicase genes of CGMMV-No. 1, CGMMV-No. 2, CGMMV-No. 3, CGMMV-No. 4 and CGMMV-No. 5 were 99.64% and 99.74%, respectively. The similarities of 129 kD and 57 kD replicase genes of CGMMV-No. 1, CGMMV-No. 3 and CGMMV-No. 4 were 99.95% and 99.94%, while they were lower between CGMMV-No. 2 and the rest of four reference sequences, just from 99.16% to 99.27% and from 99.04% to 99.18%. All reference sequences could be divided into six groups in neighbor-joining (NJ) phylogenetic trees based on the replicase gene sequences of 129 kD, 57 kD protein respectively. CGMMV-No. 1, CGMMV-No. 3 and CGMMV-No. 4 were clustered together with Shandong isolate (Accession No. KJ754195) in two NJ trees; CGMMV-No. 5 was clustered together with Liaoning isolate (Accession No. EF611826) in two NJ trees; CGMMV-No. 2 was clustered together with Korea watermelon isolate (Accession No. AF417242) in phylogenetic tree of 129 kD replicase gene of CGMMV; Interestingly, CGMMV-No. 2 was classified as a independent group in phylogenetic tree of 57 kD replicase gene of CGMMV. There were no significant hydrophobic and highly coiled coil regions on 129 kD and 57 kD proteins of tested CGMMV isolates. Except 129 kD protein of CGMMV-No. 4, the rest were unstable protein. The number of transmembrane helical segments (TMHs) of 129 kD protein of CGMMV-No. 1, CGMMV-No. 2, CGMMV-No. 3 and CGMMV-No. 5 were 6, 6, 2 and 4, respectively, which were 13, 13 and 5 on the 57 kD protein of CGMMV-No. 2, CGMMV-No. 4 and CGMMV-No. 5. The glycosylation site of 129 kD protein of tested CGMMV isolates were 2, 4, 4, 4 and 4, and that of 57 kD protein were 2, 5, 2, 5 and 2. There were difference between the disorders, globulins, phosphorylation sites and B cell antigen epitopes of 129 kD and 57 kD proteins of tested CGMMV isolates. The current results that there was no significant difference between the replicase gene sequences, it was stable and conservative for intra-species and clearly difference for inter-species. CGMMV-No. 1, CGMMV-No. 3, CGMMV-No. 4 and CGMMV-No. 5 had. a close genetic relationship with Shandong and Liangning isolates (Accession No. KJ754195 and EF611826), they are potentially originate from the same source. CGMMV-No. 2 was closer with Korea isolate. High sequence similarity of tested samples were gathered for a class in phylogenetic tree. It didn't show regularity of the bioinformatics analysis results of 129 kD and 57 kD proteins of tested CGMMV isolates. There was no corresponding relationship among the molecular phylogeny and the bioinformatics analysis of the tested CGMMV isolates.
Computational Biology ; Cucumis sativus ; chemistry ; classification ; enzymology ; genetics ; Molecular Sequence Data ; Phylogeny ; Plant Diseases ; virology ; RNA Replicase ; chemistry ; genetics ; metabolism ; Sequence Homology, Nucleic Acid ; Viral Proteins ; chemistry ; genetics ; metabolism