High-resolution mapping of the dull fruit skin gene D in cucumber (Cucumis sativus L.)

Dull/glossy fruit skin is a highly valuable external quality trait that affects the market value of cucumbers. In this study, genetic analysis showed that one single dominant gene, D (dull fruit skin), determines the dull fruit skin trait in cucumber. By combining bulked segregant analysis with 11 published polymorphic molecular markers on chromosome 5, the D/d gene was preliminarily mapped between markers SCZ69 and SSR16203, at genetic distances of 0.3 and 0.6 cM, respectively. Subsequently, a larger F2 (S06 × S94) population (842 individuals in total) was used for high-resolution mapping of the D/d gene. Finally, the D/d gene was fine-mapped between markers SSR37 and SSR112, at a physical distance of 244.9 kb (containing 31 candidate genes), using eight newly developed polymorphic simple sequence repeat (SSR) markers between SCZ69 and SSR16203. Based on semi-quantitative RT-PCR analysis, the possible candidate gene D was identified as Csa016880 or Csa016887. Meanwhile, validity analysis of the markers SSR37 and SSR112 was performed with 72 dull/glossy fruit lines, and showed that the two co-dominant SSR markers could be used for marker-assisted selection of the dull/glossy fruit trait in cucumber breeding. Moreover, this study will be helpful for cloning of the D gene in cucumber.     

Acclimation of chlorophyll biosynthetic reactions to temperature stress in cucumber (Cucumis sativus L.)

The adaptive responses of the greening process of plants to temperature stress were studied in cucumber (Cucumis sativus L. cv. Poinsette) seedlings grown at ambient (25 °C), low (7 °C) and high (42 °C) temperatures. Plastids isolated from these seedlings were incubated at different temperatures and the net syntheses of various tetrapyrroles were monitored. In plastids isolated from control seedlings grown at 25 °C, the optimum temperature for synthesis of Mg-protoporphyrin IX monoester or protochlorophyllide was 35 °C. Temperature maxima for Mg-protoporphyrin IX monoester and protochlorophyllide syntheses were shifted to 30 °C in chill-stressed seedlings. The net synthesis of total tetrapyrroles was severely reduced in heat-stressed seedlings and the optimum temperature for Mg-protoporphyrin IX monoester or protochlorophyllide synthesis shifted slightly towards higher temperatures, i.e. a broader peak was observed. To further study the temperature acclimation of seedlings with respect to the greening process, tetrapyrrole biosynthesis was monitored at 25 °C after pre-heating the plastids (28–70 °C) isolated from control, chill- and heat-stressed seedlings. In comparison to 28 °C-pre-heated plastids the percent inhibition of protochlorophyllide synthesis in 40 °C-pre-heated plastids was higher than for the control (25 °C-grown) in chill-stressed seedlings and lower than for the control in heat-stressed seedlings. Maximum synthesis of total tetrapyrroles and protoporphyrin IX was observed when chloroplasts were heated at 50 °C, which was probably due to heat-induced activation of the enzymes involved in protoporphyrin IX synthesis. Prominent shoulders towards lower or higher temperatures were seen in chill-stressed or heat-stressed seedlings, respectively. The shift in optimum temperature for tetrapyrrole biosynthesis in chill- and heat-stressed seedlings was probably due to acclimation of membranes possibly undergoing desaturation or saturation of membrane lipids. Proteins synthesized in response to temperature-stress may also play an important role in conferring stress-tolerance in plants. Received: 8 October 1998 / Accepted: 19 November 1998     

Expression analysis of defense-related genes in cucumber (Cucumis sativus L.) against Phytophthora melonis

Molecular Biology Reports - Phytophthora melonis is one of the most destructive cucumber disease, causing severe economic losses in the globe. Despite intense research efforts made in the past...     

Identification and mapping of molecular markers linked to the tuberculate fruit gene in the cucumber (Cucumis sativus L.)

Warty fruit is one of the highly valuable external quality traits related to the market values of cucumber. Genetic analysis has shown that a single dominant gene, Tu (Tuberculate fruit), determines the warty fruit trait in the cucumber plant. An F₂ population (247 individuals) from the cross of S06 × S52 was used for the mapping of the Tu/tu locus. By combining bulked segregant analysis with the sequence-related amplified polymorphism (SRAP) and simple sequence repeat (SSR) markers, 15 markers (9 SRAPs and 6 SSRs) linked to the Tu/tu locus were identified. Of nine SRAP markers, three closely linked to the Tu/tu locus were successfully converted into sequence characterized amplified region (SCAR) markers. The Tu/tu locus was mapped between the co-dominant SSR marker SSR16203 and the SCAR marker C_SC933, at a genetic distance of 1.4 and 5.9 cM, respectively. Then the linked SSR markers in the study were used as anchor loci to locate the Tu/tu locus on cucumber chromosome 5. Moreover, the validity analysis of the C_SC69 and C_SC24 markers was performed with 62 cucumber lines of diverse origins, showing that the two SCAR markers can be used for marker-assisted selection (MAS) of the warty fruit trait in cucumber breeding. The information provided in this study will facilitate the map-based cloning of the Tu/tu gene.     

Effect of ovular receptivity on seed set and fruit development in cucumber (Cucumis sativus L.)

Summary Seed set and fruit development in cucumber (Cucumis sativus L.) were studied in relation to female flower receptivity from day — 2 before anthesis to day + 2 after anthesis. The female cucumber flower is protogynous. The pistil was receptive 2 days before anthesis. The iso-electric focusing (IEF) patterns of the stigma/style proteins, were identical from day -5 to day +2. In pollinated flowers in vivo germination and pollen-tube growth in the ovary were affected by pistil age from day -2 to day +2. In addition, differences in sectorial filling in full seeds were observed within the fruits. A negative correlation was observed between the frequency of fertilized ovules in the pedoncular part of the fruit and ovary length at the time of pollination. In the whole fruit, significant differences in the number of full seeds and fruit size at maturity were found, and these were observed to be correlated with the various stages of female flower maturation at pollination. The day -2 and day +2 stages yielded the smallest fruits with few full seeds compared to the day -1, day 0 and day +1 stages, which had the biggest fruits and a large number of full seeds. A strong positive correlation was found between total seed number (including full and empty seeds), fruit length and weight at maturity. All these results suggest that both seed set in the different parts of the fruit and fruit development are controlled by ovular receptivity rather than by stigma/style receptivity.     

不同生态环境下雌雄同株黄瓜单性结实性遗传的比较

以两个单性结实性不同的雌雄同株黄瓜自交系构建的4世代群体为试材,采用植物数量性状主基因+多基因混合遗传模型联合分析方法,对南京江宁和河北昌黎两地雌雄同株黄瓜单性结实性遗传进行了比较研究.结果表明：不同生态环境下,雌雄同株黄瓜单性结实性遗传均符合E-1-1模型,受2对加性-显性-上位性主基因+加性-显性多基因控制,存在基因型与环境互作效应.但是,不同环境条件下F₁的遗传倾向和遗传参数不同,F₂的主基因遗传率为42.1%～97.5%,其遗传差异主要由黄瓜结果期两地日照和温度差异所致.强单性结实黄瓜品种选育以双亲均为强单性结实材料为宜,杂种后代宜在不同生态条件下选择鉴定.     

Molecular characterization of a transient expression gene encoding for 1-aminocyclopropane-1-carboxylate synthase in cotton (Gossypium hirsutum L.)

Ethylene performs an important function in plant growth and development. 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS), the key enzyme involved in ethylene biosynthesis, has been the focus of most ethylene studies. Here, a cotton ACS gene referred to as Gossypium hirsutum ACS1 (GhACS1), was isolated. The full-length cDNA of GhACS1 encodes for a 476-amino acid protein which harbors seven conserved regions, 11 invariant amino acid residues, and the PLP binding active site, all of which characterize ACC synthases. Alignment analysis showed that GhACS1 shared a high degree of identity with other known ACC synthases from different species. Two introns were detected in the genomic DNA sequence, and the results of Southern blot analysis suggested that there might be a multi-gene family encoding for ACC synthase in cotton. From the phylogenetic tree constructed with 24 different kinds of ACC synthases, we determined that GhACS1 falls into group II, and was closely associated with the wound-inducible ACS of citrus. The analysis of the 5' flanking region of GhACS1 revealed a group of putative cis-acting elements. The results of expression analysis showed that GhACS1 displayed its transient expression nature after wounding, abscisic acid (ABA), and CuCl(2) treatments. These results indicate that GhACS1, which was transiently expressed in response to certain stimuli, may be involved in the production of ethylene for the transmission of stress signals.     

Molecular cloning and expression analysis of spermidine synthase gene during sex reversal induced by Ethrel in cucumber (Cucumis sativus L.)

A full-length cDNA encoding spermidine synthase CsSPDS of 317 amino acids was isolated from cucumber. CsSPDS showed high similarity to SPDSs of other species, with the greatest similarity to SPDS of Coffea arabica (identity, 87%). Northern blot analysis revealed that CsSPDS was expressed predominantly in rapid growing tissues, such as roots, young leaves and flower buds. The response of CsSPDS to the sex reversal of three-leaf stage androecious cucumber seedlings by Ethrel treatment was also examined. Our results showed that the CsSPDS was up-regulated in shoot apex during sex reversal process, which correlated with increases of spermidine synthase activity and free spermidine (Spd) content, and a decrease of putrescine (Put) content in shoot apices.     

Conservation and storage of a haploid cucumber (Cucumis sativus L.) collection under in vitro conditions

 Over 3 consecutive years (1992–1994), a collection of cucumber haploids was obtained from three different lines and one hybrid. Attempts were made to maintain and store a subcollection of these haploids for 3 years. Cucumber haploids appeared to be stable when cultured in vitro. There were no instances of spontaneous doubling and only one morphologically changed plant. During the first year of storage, between 30% and 80% the clones were lost, due to disturbances in plant development, increased levels of endogenous bacteria, and physiological changes resulting in continuous flowering. After 2 years of storage haploids showed reduced vigour. Therefore, plants were regenerated directly from primordial leaf microexplants. Haploid plants were obtained from nearly all of the previous haploid plants. The rejuvenated haploids possessed the same ploidy level and morphological traits as the old collection. The only new characteristic was faster vegetative growth. Received: 17 March 1998 / Revision received: 14 April 1999 / Accepted: 10 May 1999     

The uptake and metabolism of 3H-benzylaminopurine in tobacco (Nicotiana tabacum L.) and cucumber (Cucumis sativus L.) explants

The uptake and metabolism of ³H-benzylaminopurine(³H-BAP) were studied in explanted stem pith andleaves of tobacco and in the hypocotyls and cotyledonsof cucumber. The explants were kept for 2, 5, 8 and 20h on MS medium with 0.8 mg.l^–1 2,4-D,0.5 mg.l^–1 BAP and 13.2 mg.l^–1 aspartic acid(induction medium) with or without ³H-BAP and¹⁴C-sucrose. The highest uptake of ³H-BAPwas observed in tobacco leaves and cucumbercotyledons. The major metabolite in both species was³H-benzylaminopurine riboside (³H-BAPR). Thehighest level was found in explanted cucumbercotyledons after 20 h in culture, the lowest inexplanted tobacco stem pith. Intensive 7-glucosylationof ³H-BAP was observed in explanted tobaccoleaves after 20 h in culture, where the levels of7-glucoside of ³H-BAP and of free ³H-BAPwere equal. To study the morphogenic effect of growth regulators(BAP and 2,4-D), the explants were subcultured aftershort-term induction (20 h) to MS medium without anygrowth regulators. In most cases, incubation of 20 hon induction medium was sufficient to induce therespective morphogenesis. Cucumber hypocotyl andtobacco stem pith explants formed a callus on theirbasal end. Root formation was observed on explantedcucumber cotyledons and shoot formation on tobaccoleaves. Long-term culture (3 weeks) of tobacco leaveson induction medium led to the formation of callus andglobules. The microscopic analysis of globulesindicated the presence of meristematic and tracheidalcells.