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To explore whether there is an interaction between melatonin (MT) and calcium (Ca 2+ ) in regulating heat tolerance of plants, we analyzed the response of endogenous MT and Ca 2+ to heat stress, and examined the effect of MT and Ca 2+ on the reactive oxygen (ROS) accumulation, antioxidant system, and transcripts of heat shock factor ( HSF ) and heat shock proteins ( HSPs ) of cucumber seedlings under high temperature stress. Seedlings were foliar sprayed with 100 μmol·L -1 MT, 10 mmol·L -1 CaCl 2 , 3 mmol·L -1 ethylene glycol tetraacetic acid (EGTA, Ca 2+ chelating agent) +100 μmol·L -1 MT, 0.05 mmol·L -1 chlorpromazine (calmodulin antagonist, CPZ) +100 μmol·L -1 MT, 100 μmol·L -1 p-chlorophenylalanine (p-CPA, inhibitor of MT) +10 mmol·L -1 CaCl 2 or deionized water (H 2 O), respectively. The results showed that both endogenous MT and Ca 2+ in cucumber seedlings were induced by high temperature stress. The seedlings treated with exogenous MT showed significant increases in the mRNA expression of calmodulin ( CaM ), calcium-dependent protein kinase ( CDPK5 ), calcineurin B-like protein ( CBL3 ) and CBL interacting protein kinase ( CIPK2 ) compared with the control at normal temperature. The mRNA levels of tryptophane decarboxylase ( TDC ), 5-hydroxytryptamine-N-acetyltransferase ( SNAT ) and N-acetyl-5-hydroxytryptamine methyltransferase ( ASMT ), key genes of MT biosynthesis and endogenous MT content were also induced by Ca 2+ in cucumber seedlings. Exogenous MT and CaCl 2 alleviated the heat-induced oxidative damage through increasing antioxidant ability, reducing the accumulation of reactive oxygen species (ROS), and upregulating the mRNA abundances of HSF7 , HSP70.1 and HSP70.11 , as evidenced by mild thermal damage symptoms, lower heat injury index and electrolyte leakage under heat stress. The positive effect of MT-induced antioxidant capacity and mRNA expression of HSPs was removed by adding EGTA and CPZ in stressed seedlings. Similarly, the mitigating role of Ca 2+ in the peroxidation damage to high temperature stress was reversed by p-CPA. These results suggested that both MT and Ca 2+ could induce heat tolerance of cucumber seedlings, which had crosstalk in the process of heat stress signal transduction.

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.

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.

In the present work, transgenic cucumber seedlings over expressing CsRCA and wild-type cucumber seedlings '08-1'at three-leaf stage exposed to high temperature (40 ℃, PFD 600 μmol· m -2 · s -1 ) were used to study the regulatory mechanism of photosynthesis by CsRCA. The results showed that the mRNA abundance of rbcL and rbcS as well as the activities of ribulose bisphosphate carboxylic enzyme (Rubisco) and Rubisco activase (RCA) were significantly higher in CsRCA over-expressing cucumber seedlings than in wild type (WT). Following 2-h exposure to high temperature, a notable decrease was observed in photosynthetic rate (P n ), photochemical perfor-mance index based on the absorption of light energy (PI ABS ), activities of Rubisco and RCA as well as the relative expression of rbcL, rbcS and CsRCA in both wild-type cucumber seedlings and transgenic cucumber seedlings. It was found that high temperature stress led to higher W k , a parameter of chlorophyll (Chl) a fluorescence OJIP curve. Furthermore, high temperature greatly reduced the efficiency of electron transfer along the electron transport chain beyond Q A (ψ 0 ) and the quantum yield for electron transport (φ E0 ), indicating that PSII oxygen complexes (OEC) and electron transport chain downstream Q A were inhibited by high temperature. However, the inhibition could be alleviated by over expressing CsRCA in cucumber seedlings. Taken together, our data suggested that over expressing CsRCA improves photosynthesis in cucumber seedlings under high temperature stress by enhancing activities of the Rubisco and RCA, and maintaining the number of active reaction centers.

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.

Heat shock factors (HSFs) are ubiquitous in eukaryotes with diversification in structural feature and biological function in plants. Based on the availability of whole cucumber genome sequences, we characterized the cucumber HSFs gene family which contains at least 21 members. Sequence alignments show that all HSFs possess a specific DNA binding domain (DBD). These HSFs genes are unevenly distributed in the seven cucumber chromosomes except for Csa026480 (located on Scaffold_repeat037858). Phylogenetic analysis shows that HSFs in cucumber could be divided into three families, in which family I included three categories (A, B and C). Phylogenetic tree also reveals nine pairs of orthologous genes and three pairs of paralogous genes, suggesting that HSFs gene family have existed before the separation of cucumber and Arabidopsis thaliana. EST analysis shows that cucumber HSFs may be involved in the development of fruit, female flower and hermaphrodite flower. qRT-PCR analysis demonstrated that these genes exhibit different expression levels in heat stress treatment. These results will provide a foundation for the functions of the HSF gene family.

Taking 4 different Cucurbita maxima x C. moschata rootstocks for cucumber (Cucumis sativus) as test materials, a solution culture experiment was conducted to study their growth and antioxidative enzyme activities under the stresses of Ca(NO3)2 and NaCl, with the salt stress tolerance of the rootstocks evaluated by subordinate function. At 30 mmol x L(-1) of Ca (NO3)2 or 45 mmol x L(-1) of NaCl, the growth of the rootstock seedlings was improved; but at 60 and 120 mmol x L(-1) of Ca(NO3)2 or 90 and 180 mmol x L(-1) of NaCl, the growth and the antioxidative systems of the seedlings were inhibited, and the salt injury index of 'Qingzhen No. 1' was the smallest, with the decrement of biomass and SOD, POD and CAT activities and the increment of relative conductance being significantly lower than those of the others. Under the stress of high concentration Ca(NO3)2, the SOD, POD and CAT activities of test rootstocks were higher, and the salt injury index and relative conductance were lower, as compared with those under high concentration NaCl, suggesting that the damage of Ca(NO3)2 stress to cucumber-grafted rootstock were smaller than that of NaCl stress. Among the 4 rootstocks, 'Qingzhen No. 1' had the strongest salt stress tolerance, followed by 'Zuomu Nangua', 'Fengyuan Tiejia', and 'Chaoba Nangua'.

Based on the salt-tolerance identification of a series of cucumber rootstock varieties, the cucumber cultivar 'Xintaimici' grafted on different salt-tolerant rootstock varieties 'Sherpa', 'Shintosa' , 'Tielizhen' , and 'Figleaf gourd' was selected to study its seedlings physiological responses to NaCl stress, taking the self-rooted ones as the control. Under the stress of 100 mmol NaCl x L(-1), the leaf electrolyte leakage rate and malondialdehyde (MDA) content of the grafted seedlings were significantly lower than those of self-rooted seedlings, and the seedlings grafted on 'Figleaf gourd' showed the lowest electrolyte leakage rate and malondialdehyde (MDA) content, followed by the seedlings grafted on 'Tielizhen', 'Shintosa' , and 'Sherpa'. The leaf proline and soluble sugar contents and peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities of the grafted seedlings were significantly higher than those of the self-rooted seedlings, and the POD, SOD, CAT, and APX activities were the highest for the seedlings grafted on 'Figleaf gourd' and the lowest for the seedlings grafted on 'Sherpa', but had no significant differences for the seedlings grafted on 'Tielizhen' and 'Shintosa'. The leaf Na+ content of the seedlings grafted on different rootstock varieties ranked as 'Figleaf gourd' < 'Tielizhen' < 'Shintosa' < 'Sherpa', while the leaf K+ content had little difference for the seedlings grafted on 'Figleaf gourd', 'Tielizhen', and 'Shintosa' but was significantly higher than that for the seedlings grafted on 'Sherpa'. The self-rooted seedlings had the highest leaf Na+ content but the lowest leaf K+ content. The leaf Na+/K+ ratio of grafted seedlings was significantly lower than that of self-rooted ones, and the seedlings grafted on 'Figleaf gourd' had the lowest leaf Na+/K+ ratio.

Taking the cucumber cultivar 'Jinyou 3' as test material, this paper studied the variations of the mRNA expression and activities of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco), fructose-1, 6-bisphosphatase (FBPase), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), fructose-1, 6-bisphosphate aldolase (FBA), and transketolase (TK) in cucumber seedling leaves under suboptimal temperature and low light intensity (ST+LL). In the treatment of ST+LL, the leaf area and the dry mass per plant decreased remarkably, compared with the control. On the early days of ST+LL treatment, the gene expression of Rubisco rbcL and rbcS, FBPase, GAPDH, FBA, and TK declined markedly, the activities of the enzymes except TK obviously weakened, and the photosynthetic rate (P(n)) decreased rapidly. 3 days later, the gene expression of Rubisco rbcL and rbcS and the initial activity of Rubisco showed a continuous decrease but the decrement was obviously lesser, the total activity of Rubisco and the activities and gene expression of FBPase, GAPDH, FBA, and TK had an increasing trend, and the P(n) ascended simultaneously. When the treating time exceeded 6 days, the gene expression and the activities of Rubisco and FBPase tended to be constant, while those of the other enzymes as well as the P(n) presented a decreasing trend. These results suggested that the decline of the gene expression and activities of the photosynthetic enzymes in cucumber seedlings under suboptimal temperature and low light intensity was the important reason which led to the decrease of P(n). The adaptation of photosynthetic apparatus in cucumber seedlings to suboptimal temperature and low light intensity was related to the activation mechanisms of photosynthetic enzymes.

Sex determination in plants has various mechanism; however, a single gene locus controlling unisexual expression is unique in the Cucurbitaceae plants, particularly cucumber (Cucumis sativus L.) and melon (Cucumis melo L.). In this study, with quantitative RT-PCR method, two sets of near-isogenic lines (NILs) were used to analyze the expression pattern of gene CsACS2 (GenBank accession number FJ529216). Additionally, chemical applications (AgNO3 and AVG) were used to investigate the effect of the plant endogenous ethylene on CsACS2 expression. Expression analysis reveals that endogenous ethylene, which might be derived from F or M itself, could activate the expression of M gene.

By using the mixed major gene plus polygene inheritance model of quantitative traits, a joint analysis of four-generations obtained after cross between two monoecious inbred lines was made to study the inheritance of parthenocarpy in monoecious cucumber in Jiangning (Nanjing) and Changli (Hebei). The interactions between genotype and environment were detected, and the inheritance of parthenocarpy in the monoecious cucumber was fitted in E-1-1 model and controlled by two additive-dominant-epistatic major genes and additive-dominant polygene under different eco-environments. The F1 tendency and genetic parameters of the parthenocarpy were different, and the major gene heritability of F2 ranged from 42.1% to 97.5%, which was mainly due to the differences in sunlight intensity and air temperature during fruit-setting period at the two locations. It was suggested that the parents should be highly parthenocarpic in breeding program, and the characterization of parthenocarpy should be conducted under different eco-environments.

A cDNA library was constructed from the leaves of the disease-resistant cucumber (Cucumis sativus L.) cultivar 'D0462' challenged by Pseudomonas syringae pv. Lachrymans for 48 h. The inserted fragment sizes ranged from 0.45 to 2.1 kb and the average inserted size was 1 kb. Sequencing analysis showed that 2 352 TUTs (Tentative unique transcripts), 282 contigs, and 2 070 singlets were identified in the 2 966 ESTs derived from the cDNA library. The result of the BlastX analysis indicated that there were 1 848 ESTs with known or unknown function, 504 ESTs with no significant similarity matching with any protein or DNA sequence in the databases. In this library, many defense/disease-resistant related genes, such as metallothionein, glutathione S-transferase, ubiquitin, b-1, 3-glucanase, zinc finger protein, and cysteine protease, which might participate in the plant and the pathogens, are inclued.

This paper studied the relative expression of Mn-SOD, Cu/Zn-SOD and CAT mRNAs and the changes of SOD, Mn-SOD, Cu/Zn-SOD and CAT activities in grafted and own-rooted cucumber leaves under low temperature stress, and their relations with the cold resistance of cucumber. For both grafted and own-rooted cucumber leaves, the relative expression of Mn-SOD and Cu/Zn-SOD mRNAs under low temperature stress was respectively accordance with the changes of Mn-SOD and Cu/Zn-SOD activities, while the expression of CAT mRNA was not accordance with the change of CAT activity. The relative expression of Mn-SOD and Cu/Zn-SOD mRNAs and the activities of SOD, Mn-SOD and Cu/Zn-SOD in grafted cucumber leaves were higher than those in own-rooted cucumber leaves, while the MDA content and electrolytic leakage were in adverse. The higher SOD activity regulated by the higher SOD mRNAs expression in grafted cucumber leaves might be the key factor of grafted cucumber having a higher cold resistance to low temperature stress than own-rooted cucumber. The relative expression of CAT mRNA was slightly higher in functional leaves but lower in young leaves of grafted cucumber, while less difference was observed in CAT activity, comparing with own-rooted cucumber, which illustrated that low temperature stress had lesser effects on the relative expression of CAT mRNA and the activity of CAT in grafted cucumber leaves.

Taking grafted and own-root cucumber (Junlv No. 3) plants as test materials, the changes of their leaf Cu/Zn-SOD, Mn-SOD and CAT mRNA relative expression, leaf SOD, Cu/Zn-SOD, Mn-SOD and CAT activities, leaf MDA content, and leaf electrolytic leakage under NaCI stress were studied. The results showed that under NaCl stress, grafted cucumber had a higher relative expression of its leaf Cu/Zn-SOD, Mn-SOD and CAT mRNA, and higher activities of its leaf SOD, Cu/Zn-SOD, Mn-SOD and CAT, compared with own-root cucumber, which suggested that the higher relative expression of Cu/Zn-SOD, Mn-SOD and CAT mRNA in grafted cucumber leaves resulted in the higher activities of their SOD, Cu/Zn-SOD, Mn-SOD and CAT. With the NaCl stress prolonged, the relative expression of Cu/Zn-SOD, Mn-SOD and CAT mRNA in both grafted and own-root cucumber leaves had an increasing trend, but the changing trend of Cu/Zn-SOD, MnSOD and CAT activities were not the same as that of mRNA, indicating that the activities of SOD and CAT were also regulated by other factors. The leaf MDA content and electrolytic leakage of grafted cucumber were lower than those of own-root cucumber, suggesting that grafted cucumber had a higher scavenging metabolism, which could decrease oxidative damage and increase its salt-tolerance.

This paper reported the synergistic effect of KT and IAA, and the effects of age of seedlings, length of hypocotyls, nitrogen contents and NH(+)(4)-N/TN ratio on the induction of female flowers in derooted seedlings of Cucumis sativus L. for the establishment of an efficient system for the induction of female flowers. When cultured on MS basal medium supplemented with KT 3.0 mg/L and IAA 0.01 mg/L, an induction rate of 28% was obtained for the 7-day-old derooted seedlings with 1/2 hypocotyl, 12% and 26% higher than when cultured with KT 3.0 mg/L alone and IAA 0.01 mg/L alone, respectively, while no female flowers was formed on the control medium, which indicates that KT and IAA have an evident synergistic effect on the induction of female flowers. Experiment was done with N concentration of 60-90 mmol/L or with NH(+)(4)-N/TN ratio of 12.5%-50% (total N kept at 80 mmol/L), with lengths of hypocotyls of 0-4/4, and with different ages of seedlings of 5-8-day-old, the highest induction rate of 40%, 48% and 57% for female flowers was achieved on medium of N 80 mmol/L (NH(+)(4)-N/TN 37.5%), from seedlings with 1/4 hypocotyl and from the treatment using 6-day-old seedlings respectively.

When SRAP (Sequence-Related Amplified Polymorphism) marker was used in constructing genetic map and analyzing QTL for high temperature resistance in cucumber (Cucumis sativus L.), it exhibited certain characteristics in detecting genomic polymorphism. When each forward primer was combined with different reverse primers, the number of primer combinations that produced polymorphism ranged from five to eight. When each reverse primer was in combination with different forward primers, the number of polymorphic primer combinations ranged from two to eleven. The reverse primers SA4 or EM6 produced identical polymorphic bands when combined with all the forward primers tested. These bands might be amplified by the reverse primers. The polymorphic bands amplified from OD3ME11 co-segregated in the F2 population. The utilization of these characteristics in our research was discussed.

Basing on the fragment (CO434610) cloned from cDNA amplified fragment length polymorphism (cDNA-AFLP), a 1191-bp cDNA sequence of CsEXP10 with a complete 3' end was obtained via rapid amplification of cDNA ends (RACE) and getting spliced with an EST (AF319471) of the same gene (Fig.2). Southern blotting analysis showed that CsEXP10 was a single copy gene in cucumber (Fig.5). The transcripts of CsEXP10 were detected by RT-PCR only in young fruit 3 d after pollination, but not in root, stem, and leaf (Fig.4A). At different developmental stages of fruit growth, Northern blotting demonstrated that CsEXP10 gene was expressed strongly in fruit 3 d and 10 d after pollination, especially the latter, but undetectable in ovaries of 2-3 cm in length and without pollination on the day flowering, and in fruits 26 d after pollination (Fig.4B). It is suggested that CsEXP10 might be highly correlated with the expansive growth of cucumber fruit.

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.

The plantlets of soybean, cucumber and garden balsam were inoculated by wild-type Agrobacterium rhizogenes K599, and hairy root was induced on inoculated sites in vivo. The frequencies of hairy root induction from wound cotyledons of soybean, cucumber and garden balsam were 100%, 65% and 91%, respectively. Moreover, hairy root was induced from healthy cucumber axillary bud with frequency of 10%. PCR analysis of hairy root DNA was conducted using the primers from rolC gene. The PCR results showed that all hairy root lines contained T-DNA. The established system should be ideal for studying soybean and cucumber nematode and garden balsam breeding of flower dwarf architecture.

Differential expression of genes in young fruit of cucumber (Cucumis sativus L.) before/after pollination was investigated via cDNA amplified fragment length polymorphism (cDNA-AFLP). There were 64 transcript-derived fragments (TDFs) displayed specially in young fruits after pollination of 6-72 h (Table 1), five of which were verified to be mainly expressed in young fruits by reverse Northern dot blotting (Fig.2). Sequence data showed one TDF was a new gene encoding expansin and was named as Cs-Expansin10 (CsExp10), which might be related to the expanding growth of cucumber fruit after pollination (Fig.3), another was significantly similar to the glutathione reductase gene, and the others had no similar sequence in GenBank database (Table 2).

A cDNA fragment that encodes auxin-binding protein 1 was amplified by, reverse polymerase chain reaction from ovary of cucumber. Its expression signals were weak in the ovary of 1 d before anthesis, while got strong in 2, 4 and 6 d after pollination. Among the unpollinated ovary of 2 d after anthesis, those that got enlarged had strong expression signals; the others that were wilting had weak signals. This indicated that auxin-binding protein 1 gene possibly play a role in cucumber fruit development. When auxin-binding protein 1 gene of Arabidopsis was transformed into cucumber, the parthenocarpic rate of transgenic plants was 31.7%, higher than the control. This result showed that the sensibility to auxin was increased in transgenic plants.

CFL gene, a LFY homologue, was cloned from cucumber (Cucumis sativus L.). In this paper, in situ hybridization was performed to analyze the expression pattern of CFL gene at the stage of floral and vegetative buds differentiation in cucumber cotyledonary nodes cultured in vitro. The results showed that at the stage of floral differentiation, CFL gene was strongly expressed in primordia, floral organ primordia, and each whirl of floral organs at the early stage of their formation, but weakly expressed or not expressed in floral organs after their formation (Fig. 2). At the stage of vegetative bud differentiation, CFL gene was strongly expressed in meristem, leaf primordium and young leaves, and no apparent expression signal was detected in mature tissues (Fig. 3). The results suggest that the expression of CFL gene be necessary for the differentiation and formation of floral and vegetative primordias, and it plays an important role in floral and vegetative development in cucumber. The results also indicate that CFL gene involving in mitosis initiation, mitosis controlling, and transformation of vegetative meristem to floral meristem.

Four kinds of mitochondrial plasmid-like DNA, designated pC1, pC2, pC3 and pC4, have been found in cucumber (Jinyan No. 4). Their distribution in 14 Cucumber varieties was analyzed. Plasmid-like DNAs were detected in Jinchun No. 2, Jinchun No. 5, Jinxinmici, Jinlu No. 4 and Jinyan No. 4, and the rest 9 varieties contained no plasmid-like DNAs, suggesting that their distribution is irregular. There was homology among the same plasmid-like DNA family in different varieties. pC4 showed homology to the nuclear DNA of Jinyan No. 4, in addition to the nuclear genomes of other 7 varieties either with plasmid-like DNAs or without. The homologous sequences of pC4 in the cucumber nuclear DNA were repetitive. Sequences homologous to pC4 were also found in the nuclear genomes of towel gourd and pumpkin (other cucurbitaceous plant). Therefore, we propose that mitochondrial plasmid-like DNA occurred before cucumber diverged from cucurbit and had integrated into the nuclear DNA. The varieties without plasmid-like DNAs might lost them during evolution.

Four kinds of plasmid-like DNA, designated pC1, pC2, pC3 and pC4 were found in the mitochondrion of cucumber Jinyan No. 4. The circle plasmid-like DNA pC1 was cloned into the EcoR I site of pUC19 using E. coli JM109 as host. The cloned pC1 DNA was isolated and used as probes in Southern analyses of total mitochondrial DNA, nuclear DNA and chloroplast DNA. Evidences were obtained that the pC1 did not show any homology with nuclear, chloroplast, main mitochondrial genomes and the other plasmid-like DNAs. Sequence analysis revealed that pC1 was 2,889 bp long. It contained many forward and reverse repeat sequences. Three main open reading frames in pC1 were longer than 800 bp. Computer-assisted searching the nucleotide sequence in GenBank database revealed pC1 had no significant homology with known sequences of mitochondrial and plasmid-like DNA, but had homology with the E. coli, Mycobaterium tuberculosis and Anacystis nidulans genomes. The predicted proteins of pC1 main ORFs show homology with the sulfate transport system in bacteria, alga and liverwort. It suggested that pC1 may encode functional proteins.