Auxin,biosynthesis of ethylene and sex expression in cucumber (Cucumis sativus)

Ethylene production, level of 1-aminocyclopropane-1-carboxylic acid (ACC) and activity of the ethylene forming enzyme (EFE) were higher in apices of gynoecious cucumber (Cucumis sativus cv. Alma) as compared to monoecious cucumber (C. sativus cv. Elem). Application of indole-3-acetic acid (IAA) enhanced ethylene and ACC production in both cultivars. The stimulatory effect of IAA was more pronounced in gynoecious apices. Induction of ethylene production and accumulation of ACC resulting from treatment with IAA were effectively blocked by aminoethoxyvinylglycine (AVG). Content of endogenous IAA, measured by an enzyme immunoassay, was lower in gynoecious cucumber as compared to monoecious one. Treatment of gynoecious plants with the antiauxins -(p-chlorophenoxy)isobutyric acid (PCIB) and -naphthaleneacetic acid (-NAA) did not inhibit female sex expression.It appears that although exogenous IAA enhances ACC and ethylene production, endogenous IAA might not have a major role in the control of sex expression in cucumber of the Beit-Alfa type.Prof. Rudich passed away in May 1986.     

Ethylene evolution from cucumber plants as related to sex expression

Ethylene evolved from monoecious and gynoecious cucumber (Cucumis sativus) plants grown under short and long day conditions was determined. More ethylene was evolved from floral buds and apices bearing buds than from whole seedlings of comparable weight. More ethylene also was evolved from apices of the gynoecious than from those of the monoecious type. Furthermore, quantities evolved from female buds were greater than from male ones and plants grown under short day conditions which promote femaleness evolved more ethylene than those grown under long day conditions. The data suggest that ethylene participates in the endogenous regulation of sex expression by promoting femaleness.     

Correlation between development of female flower buds and expression of the CS-ACS2 gene in cucumber plants

Ethylene plays a key role in sex determination of cucumber flowers. Gynoecious cucumber shoots produce more ethylene than monoecious shoots. Because monoecious cucumbers produce both male and female flower buds in the shoot apex and because the relative proportions of male and female flowers vary due to growing conditions, the question arises as to whether the regulation of ethylene biosynthesis in each flower bud determines the sex of the flower. Therefore, the expression of a 1-aminocyclopropane-1-carboxylic acid synthase gene, CS-ACS2, was examined in cucumber flower buds at different stages of development. The results revealed that CS-ACS2 mRNA began to accumulate just beneath the pistil primordia of flower buds at the bisexual stage, but was not detected prior to the formation of the pistil primordia. In buds determined to develop as female flowers, CS-ACS2 mRNA continued to accumulate in the central region of the developing ovary where ovules and placenta form. In gynoecious cucumber plants that produce only female flowers, accumulation of CS-ACS2 mRNA was detected in all flower buds at the bisexual stage and at later developmental stages. In monoecious cucumber, flower buds situated on some nodes accumulated CS-ACS2 mRNA, but others did not. The proportion of male and female flowers in monoecious cucumbers varied depending on the growth conditions, but was correlated with changes in accumulation of CS-ACS2 mRNA in flower buds. These results demonstrate that CS-ACS2-mediated biosynthesis of ethylene in individual flower buds is associated with the differentiation and development of female flowers.     

Identification of a 1-aminocyclopropane-1-carboxylic acid synthase gene linked to the female (F) locus that enhances female sex expression in cucumber.

Sex determination in cucumber (Cucumis sativus L.) is controlled largely by three genes: F, m, and a. The F and m loci interact to produce monoecious (M_f_) or gynoecious (M_f_) sex phenotypes. Ethylene and factors that induce ethylene biosynthesis, such as 1-aminocyclopropane-1-carboxylate (ACC) and auxin, also enhance female sex expression. A genomic sequence (CS-ACS1) encoding ACC synthase was amplified from genomic DNA by a polymerase chain reaction using degenerate oligonucleotide primers. Expression of CS-ACS1 is induced by auxin, but not by ACC, in wounded and intact shoot apices. Southern blo hybridization analysis of near-isogenic gynoecious (MMFF) and monoecious (MMff) lines derived from divers genetic backgrounds revealed the existence of an additional ACC synthase (CS-ACS1G) genomic sequence in the gynoecious lines. Sex phenotype analysis of a segregating F2 population detected a 100% correlation between the CS-ACS1G marker and the presence of the F locus. The CS-ACS1G gene is located in linkage group B coincident with the F locus, and in the population tested there was no recombination between the CS-ACS1G gene and the F locus. Collectively, these data suggest that CS-ACS1G is closely linked to the F locus and may play a pivotal role in the determination of sex in cucumber flowers.     

Sex expression in cucumber plants as affected by mechanical stress

Sex expression in cucumber plants, as affected by mechanicalstress, was examined using 4 cultivars with different geneticbackgrounds for sex expression. Mechanical stress given to theplant greatly reduced growth and increased the number of pistillate(female) flowers in the monoecious type, but it had no effecton the sex expression of the gynoecious type. The effect ofmechanical stress on the growth and sex expression of the monoecioustype was nullified by the foliar application of gibberellinA₄₊₇. Silver nitrate also was effective in nullifying the effectof mechanical stress on sex expression, but not the effect ofgrowth retardation. Pistillate flowers in a gynoecious strainwere reduced by silver nitrate. (Received October 18, 1979; )     

Isolation of a partial sequence of a putative nucleotide sugar epimerase, which may involve in stamen development in cucumber (Cucumis sativus L.)

Sex determination is the most widely studied subject in cucumber. The sex of cucumber plants can be monoecious, hermaphrodite, gynoecious, androecious, or andromonoecious. Besides environmental factors, three major genes, F/f, M/m, and A/a mainly govern the sex types in cucumber. Regardless of their sex all floral buds are bisexual at the early bud stage. A stage specific arrest of either stamen or carpel leads to unisexual flower development. The possible downstream product of the interaction of the sex determining genes that may directly allow the growth or selectively arrest stamen or pistil is not yet identified. Therefore, in the current study, we performed suppression subtractive hybridization using floral buds from nearly isogenic gynoecious and hermaphrodite cucumber plants and identified for the first time a cDNA homologous to nucleotide sugar epimerase. The expression level of the isolated putative nucleotide sugar epimerase is weak in female floral buds but strong in bisexual and male flowers. The weak level of the putative nucleotide sugar epimerase may be an indication for its improper functioning, which may influence stamen development in cucumber plants.     

Characterization of ethylene effects on sex determination in cucumber plants

Sex differentiation in cucumber plants (Cucumis sativus L.) appears to be determined by the selective arrest of the stamen or pistil primordia. We investigated the influence of an ethylene-releasing agent (ethephon) or an inhibitor of ethylene biosynthesis (aminoethoxyvinyl glycine) on sex differentiation in different developmental stages of flower buds. These treatments influence sex determination only at the stamen primordia differentiation stage in both monoecious and gynoecious cucumbers. To clarify the relationships between the ethylene-producing tissues and the ethylene-perceiving tissues in inducing female flowers in the cucumber, we examined the localization of mRNA accumulation of both the ACC synthase gene (CS-ACS2) and the ethylene-receptor-related genes (CS-ETR1, CS-ETR2, and CS-ERS) in flower buds by in situ hybridization analysis. CS-ACS2 mRNA was detected in the pistil primordia of gynoecious cucumbers, whereas it was located in the tissues just below the pistil primordia and at the adaxial side of the petals in monoecious cucumbers. In flower buds of andromonoecious cucumbers, only CS-ETR1 mRNA was detected, and was located in the pistil primordia. The localization of the mRNAs of the three ethylene-receptor-related genes in the flower buds of monoecious and gynoecious cucumbers overlap but are not identical. We discuss the relationship between the mRNA accumulation patterns and sex expression in cucumber plants.     

Sexual differentiation in cucumber: The effects of abscisic acid and other growth regulators on various sex genotypes

AbA, ethephon and gibberellin were applied to cucumber plantsof monoecious, gynoecious, andromoneocious and hermaphroditeinbred lines, as well as to F₁ (gynoecious?monoecious) plants.Exogenous AbA enhanced the male tendency in monoecious cucumberplants and the female tendency in gynoecious plants, irrespectiveof light regime. Exogenous ethephon treatments increased thefemale tendency in monoecious plants, and decreased it in gynoeciousones. These effects were influenced by day length. ExogenousAbA counteracted the effect of gibberellin (A₄₊₇) treatmentin gynoecious plants, but had no such effect in monoecious ones. In addition to its differential effect on sexual differentiation,AbA stimulated flower development in gynoecious plants and inhibitedit in monoecious plants. These responses to AbA are discussedin the light of previously reported effects of plant growthregulators on various sex types of cucumber. The present resultsare being integrated into an updated working hypothesis on sexcontrol in cucumbers. (Received August 30, 1976; )     

The level of phytohormones in monoecious and gynoecious cucumbers as affected by photoperiod and ethephon

The endogenous levels of auxin, gibberellin, and inhibitors were followed in monoecious and gynoecious cucumber (Cucumis sativus L.) plants, and in plants treated with the ethylene-releasing compound Ethephon (2-chloroethyl phosphonic acid). Higher auxin inhibitor and lower gibberellin levels were associated with female tendency. The endogenous level of gibberellin and auxin decreased in Ethephon-treated plants. Application of Ethephon induced a rise in abscisic acid. Root application of abscisic acid promoted female tendency of gynoecious cucumbers grown under conditions which increase maleness. High CO₂ levels, which are known to antagonize ethylene, increased maleness of gynoecious cucumbers. The possibility of interrelationship between gibberellin, auxin, ethylene, and abscisic acid on sex expression are discussed.     

The M locus and ethylene-controlled sex determination in andromonoecious cucumber plants.

Sex determination in cucumber (Cucumis sativus L.) plants is genetically controlled by the F and M loci. These loci interact to produce three different sexual phenotypes: gynoecious (M-F-), monoecious (M-ff), and andromonoecious (mmff). Gynoecious cucumber plants produce more ethylene than do monoecious plants. We found that the levels of ethylene production and the accumulation of CS-ACS2 mRNA in andromonoecious cucumber plants did not differ from those in monoecious plants and were lower than the levels measured in gynoecious plants. Ethylene inhibited stamen development in gynoecious cucumbers but not in andromonoecious ones. Furthermore, ethylene caused substantial increases in the accumulation of CS-ETR2, CS-ERS, and CS-ACS2 mRNA in monoecious and gynoecious cucumber plants, but not in andromonoecious one. In addition, the inhibitory effect of ethylene on hypocotyl elongation in andromonoecious cucumber plants was less than that in monoecious and gynoecious plants. These results suggest that ethylene responses in andromonoecious cucumber plants are reduced from those in monoecious and gynoecious plants. This is the first evidence that ethylene signals may influence the product of the M locus and thus inhibit stamen development in cucumber. The andromonoecious line provides novel material for studying the function of the M locus during sex determination in flowering cucumbers.     

Photoperiodic regulation of CS-ACS2, CS-ACS4 and CS-ERS gene expression contributes to the femaleness of cucumber flowers through diurnal ethylene production under short-day conditions

Photoperiod and the plant hormone, ethylene, modify sex expression of flowers in cucumber (Cucumis sativus L.). In the present study, femaleness of cucumber occurred under short‐day (8 h photoperiod) conditions compared to that under long‐day (16 h photoperiod) conditions, although the effect of photoperiod was more pronounced in a monoecious than in an andromonoecious cucumber. Application of ethylene had a greater effect than photoperiod on the production of female and bisexual flowers in monoecious and andromonoecious cucumbers, respectively. Ethylene evolution and the expression of CS‐ACS2, CS‐ACS4 and CS‐ERS genes in the shoot apices of both monoecious and andromonoecious cucumber plants had a diurnal rhythm with a peak in the middle of an 8 h or a 16 h light period. Peak ethylene evolution and expression of CS‐ACS2 was greater under short‐day conditions than under long‐day conditions in a monoecious cucumber but not in an andromonoecious one. Expression of CS‐ACS4 in monoecious and andromonoecious cucumber plants did not differ, but the level was higher under short‐day conditions compared with that under long‐day conditions. Thus, CS‐ACS2 and CS‐ACS4 might be involved in the basic diurnal rhythm of ethylene evolution in cucumber. Because exogenous ethylene increased the expression of CS‐ACS2 and CS‐ERS in monoecious cucumber possessing the M locus, but not in andromonoecious cucumber in which the function of the M locus was lost (Yamasaki et al. Plant and Cell Physiology 42, 608–619, 2001), the CS‐ACS2 gene might also be involved in ethylene production by positive feedback via regulation of M locus under short‐day conditions.     

黄瓜植株性别表现与3种氧化酶同工酶的关系

采用同工酶电泳技术分析了二叶期纯雌株和雌雄株黄瓜（Ｃｕｃｕｍｉｓ ｓａｔｉｖｕｓ Ｌ．）子叶和真叶过氧化物酶、多酚氧化酶和超氧化物歧化酶同工酶,结果发现：给株比雌雄株酶活性强、酶带数量多,这种差异酶带大多与雌性或雌雄性别紧密相关,经检验可以作为黄瓜雌性株早期鉴定的生化标记,尤其以真叶中多酚氧化酶同工酶Ｒｆ０．２８７表现稳定,鉴定成功率高。等电聚焦电泳垂直平板聚丙烯酰胺凝胶电泳分辨效果好。     

Peroxidase and IAA Oxidase Activity and Isoenzyme Patterns in Cucumber Plants, as Affected by Sex Expression and Ethephon

Peroxidase and IAA-oxidase activity, electrophoretic patterns of total proteins and isoenzymes and the effect of Ethephon (= Ethrel, 2-chloroethane phosphonic acid) on these patterns were compared in extracts of monoecious and gynoecious cucumber plants. The activity of both peroxidase and IAA oxidase was greater in gynoecious than in monoecious plants. Ethephon treatments given at the 2-leaf stage increased peroxidase activity, especially in monoecious plants, and decreased IAA-oxidase activity. Ethephon treatment did not affect total protein or isoenzyme patterns, but increased band intensity, especially that of one band in monoecious plant extracts. No differences between monoecious and gynoecious plants were found in total protein, peroxidase and IAA-oxidase isoenzyme patterns. Peroxidase and IAA-oxidase activity sites on the gel were similar.     

黄瓜茎端ABA/GA_4比值与花芽性别分化的关系(英文)

在同一环境条件下,单雌性株茎端ABA含量显著高于雌雄同株的,而GA_4水平却正好相反。 较高的ABA/GA_4比值有利于黄瓜雌性分化,反之则有利于雄性分化。促进黄瓜雄性分化的生长物质GA_3和AgNO_3会引起黄瓜茎端ABA/GA_4比值的下降,而促进其雌性分化的生长物质乙烯利(Ethrel)则会引起ABA/GA_4比值的上升。     

Contents and recovery of gibberellins in monoecious and gynoecious cucumber plants

Diffusates from seedlings and root exudates from 6-week-old plants of a monoecious line of cucumber, Cucumis sativus L., contained considerably higher levels of gibberellin-(GA-) like substances than did those from plants of an isogenic gynoecious line. Most of the GA-like activity was found in a chromatogram region typical of GA₁ and GA₃; some activity, particularly in root exudates, appeared also at an R_F similar to that of GA₄ and GA₇.

When seedlings were treated with ³H-labeled GA₁, more radioactivity was found in the diffusates from monoecious seedlings than from gynoecious ones. The same was true of biological activity in root diffusates from older plants which had been treated with gibberellin A₄₊₇.

In conjunction with evidence present in literature, these results support the idea that endogenous GAs play a part in the regulation of sex expression in cucumber, relatively high levels favoring the formation of staminate flowers.