Involvement of polyamines in gibberellin-induced development of seedless grape berries

The roles of polyamines (PAs) in the development of seedless grape berries induced by gibberellin (GA₃) was investigated. The development of seedless grape berries was stimulated by the application of putrescine (Put), but not by that of spermidine (Spd) and spermine (Spm), regardless of the presence of GA₃. At harvest, the fresh weight of seedless grape berries treated with 500 ppm Put + 25 ppm GA₃ and 500 ppm Put increased to 111 and 112%, respectively, of the control. Treatment with methylglyoxal-bis (guanyl hydrazone), a potent inhibitor of S-adenosylmethionine decarboxylase that plays a role in Spd and Spm synthesis, did not affect the development of seedless grape berries induced by 100 ppm GA₃. The application of 100 ppm GA₃ significantly increased endogenous free Put levels. Levels of free Spd and Spm were not affected by GA₃. Although the levels of endogenous perchloric acid insoluble bound PAs were higher than those of free PAs, obvious changes in the levels of bound PAs were not observed. These results indicate that free Put is implicated in the development of seedless grape berries induced by GA₃.     

Changes in contents and antioxidant activity of phenolic compounds during gibberellin-induced development in <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. ‘Muscat’

Gibberellic acid (GA₃) is a plant growth regulator commonly used for increasing the productivity of seedless fruit. However, little is known about the effect of GA₃ on phenolic compounds in grapevine. In the present study, the effect of GA₃ application on contents and antioxidant activities of phenolic compounds in different tissues of Muscat grapevine (Vitis vinifera L. cv. Muscat) was investigated. An application of 100 mg/L GA₃ could successfully induce seedless grape berry, enhance berry size and accelerate the development of berries, resulting in earlier ripening of seedless berry. The contents of total phenolics and total flavonoids, and antioxidant activities in leaf, stem and tendril obviously increased, while these remarkably decreased in berry skin and flesh after GA₃ application. In addition, the grapevine leaf, stem, tendril and skin extracts were shown to contain high amounts of phenolics and significant antioxidant activities. Thus, these findings indicate that GA₃ application causes different effect on phenolic compounds and antioxidant activities, depending on grapevine tissues.     

Using urea phosphate to enhance the effect of gibberellin A3 on grape size

Gibberellic acid (GA₃) is widely used to enlarge the berries of seedless grapes (Vitis vinifera L). In cv. Sultana (Thompson Seedless) the addition of 1000 mg/L urea phosphate (UP) to GA₃ solutions after fruit set reduced the pH of the solutions to a stable pH 2.9 and enhanced the effect of GA₃ on berry size and delayed maturation. Addition of citrate buffer, pH 2.9, to GA₃ sprays did not affect berry size or maturation. The possibility of improved GA penetration due to the low pH is considered. The nutritional effect of UP and direct enhanced penetration by the urea ion are also discussed.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 1735-E, 1986 series.     

Roles of gibberellins in increasing sink demand in Japanese pear fruit during rapid fruit growth

Our previous work demonstrated that exogenous gibberellins (GAs) applications during rapid fruit growth significantly increases sink demand and results in a larger fruit in Japanese pear. In an attempt to unravel the mechanism of increased sink demand by applied GAs, the histology, cell wall components of the flesh, and carbon accumulation in the fruit were assessed for Japanese pear (Pyrus pyrifolia, cultivar ‘Kousui’), as were the activities of sucrose- and sorbitol-cleaving enzymes. Our results show that most vascular tissues occurred in core tissue with very little vascular tissue in the flesh. Application of a mixture of GA₃ + GA₄ in lanolin paste significantly increased the amount of ethanol-insoluble solids, e.g., total pectins, hemicellulose, and cellulose in the cell walls. There was a significantly increased sink demand (assessed by ¹³C accumulation in the fruit) by the applied GAs, and this increased sink strength was closely related to increased activities of cell wall-bound invertase in the core, neutral invertase and NAD-dependent sorbitol dehydrogenase in the flesh during rapid fruit growth. As well, concentrations of sorbitol and sucrose in the flesh were decreased by GA application, while glucose concentration increased. Most importantly, the fact that sink activity can be increased by GA application implies that endogenous GAs are likely to be important modulators for sugar metabolism. Hence, selecting for genotypes with elevated GA production in the growing fruit and increased activities of key enzymes for sugar metabolism could result in increased fruit size.     

Role of ABA and Gibberellin A<Subscript>3</Subscript> on gene expression pattern of sugar transporters and invertases in <Emphasis Type="Italic">Vitis vinifera</Emphasis> cv. Malbec during berry ripening

Sugars are key constituents that affect quality of grape berries, and consequently the grape metabolic profile relevant to wine’s industry. However, enzymes and transporter genes expression involved in sugar transport at different phenological stages are scarcely studied. In addition, little is known about the role of the plant hormones ABA and Gibberellin (GA₃) as endogenous regulators, over the expression pattern of the sugars transporters genes in grapevine. The aim of this study was to analyze the expression pattern of the most relevant sugar transporters and invertases in leaves and berries of grapevine plants cv. Malbec during berry ripening stages and its shift after ABA and GA₃ sprays. In leaves, VvHT1 was the sugar transporter highly expressed, whereas VvHT6 was the most abundant in berries throughout berry ripening. Moreover, VvSUC12 and VvSUC27 were expressed at veraison greater in leaves than in berries, suggesting an active phloem loading at the onset of ripening. Applications of ABA and GA₃ enhanced the expression of VvSUC12 and VvSUC27 in pre-veraison leaves. Furthermore, hormones increased the expression of VvHT2, VvHT3 and VvHT6 in berries at different stages of ripening favoring sugar unloading from phloem. In conclusion, ABA and GA₃ are involved in the long-distance sugar transport from leaves to berries in Vitis vinifera L. cv. Malbec, and their exogenous application could be a suitable strategy to improve the process.     

ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non‐structural carbohydrates in leaves,enhancement of phloem area and expression of sugar transporters

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A₃ (GA₃) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot‐grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA₃ solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre‐veraison, full veraison and post‐veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA‐treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA₃ increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA₃ to berries and stems, respectively, was due to build‐up of non‐structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.     

Sucrose metabolism and fruit growth in parthenocarpic vs seeded blueberry (Vaccinium ashei) fruits

Although fruit set and development are induced by applications of gibberellins, final fruit weight of gibberellin-induced parthenocarpic fruit is often less than that of pollinated fruit. We examined changes in the activities of sucrose-metabolizing enzymes and sugar accumulation in developing fruits of cultivated blueberry (Vaccinium ashei Reade) and their correlation with fruit growth upon pollination or exogenous applications of gibberellic acid (GA₃). The objective was to determine if differences in fruit growth could be attributed to differences in enzyme activities and subsequent sugar accumulation in fruits. The fruit development period of GA₃-treated fruits was 15 days longer than that of pollinated fruits. At maturity, GA₃-treated fruit accumulated an average of 180 mg dry weight while pollinated fruit accumulated 390 mg dry weight. Dry weight accumulation in nonpollinated fruits was negligible and these fruits abscised by 45 days after bloom (DAB). The total carbon (C) cost (dry weight C + respiratory C) for fruit development was 109 and 244 mg C fruit^-1 for GA₃-treated and pollinated fruits, respectively. Hexose concentration increased to 100 mg (g fresh weight)^-1 at ripening in both GA₃-treated and pollinated fruits. Nonpollinated fruits reached a maximum hexose concentration at 45 DAB. Sucrose phosphate synthase (EC 2.4.1.14) and sucrose synthase (EC 2.4.1.13) activities reached a maximum of ≤5.0 μmol (g fresh weight)^-1 h^-1 in both GA₃-treated and pollinated fruits. Soluble acid invertase (EC 3.2.1.26) activity increased to about 60 μmol (g fresh weight)^-1 h^-1 in both GA₃-treated and pollinated fruits at ripening, while in nonpollinated fruits, a maximum soluble acid invertase activity of 0.12 μmol (g fresh weight)^-1 h^-1 was measured at 24 DAB. Insoluble acid invertase activity declined during the early stages of fruit growth and remained relatively low throughout fruit development. Neutral invertase activity was low throughout development, increasing to 5 μmol (g fresh weight)^-1 h^-1 at ripening in GA₃-treated and pollinated fruits. Our studies demonstrate that blueberry fruit development does not appear to be limited by sucrose metabolizing enzyme activity and/or the ability to accumulate sugars in either GA₃-treated or pollinated fruits.     

Study on russet-related enzymatic activity and gene expression in ‘Shine Muscat’ grape treated with GA3 and CPPU

Physiological (metabolite analysis) and molecular (gene expression) approaches were used to understand the mechanism underlying russet formation in response to the application of GA₃ and CPPU (Forchlorfenuron) in a Japanese table grape cultivar ‘Shine Muscat’. Several different concentrations of GA₃ and GA₃?+?CPPU [25?mg?L^?1 GA₃ (A), 25?mg?L^?1 GA₃?+?5?mg?L^?1 CPPU (B), 25?mg?L^?1 GA₃?+?10?mg?L^?1 CPPU (C), and 25?mg?L^?1 GA₃?+?15?mg?L^?1 CPPU (D)] were applied to grape berry clusters at two weeks after flowering (WAF). No russet was observed on the berries treated with the ‘C’ combination. Lower levels of phenylalanine ammonia-lyase (PAL) activity was observed in the treated samples, relative to the untreated material. Reduced peroxide (POD) activity was also observed in response to different treatments, while the expression of Peroxidase 17 and Phenylalanine ammonia-lyase G1 genes mirrored lignin content. Increased activity of 4-coenzyme A ligase (4CL) may contribute to decreasing the level of russet and help to improve grape berry quality.     

Proteomic analysis of berry-sizing effect of GA3 on seedless Vitis vinifera L

Gibberellin (GA) is widely used in the table grape and raisin industries to enlarge the berries of seedless varieties. However, the mechanism underlying its berry‐sizing effect is poorly understood. In this study, clusters of Centennial Seedless (Vitis vinifera L.) were treated with 30 ppm GA₃ on day 12 after flowering, and berries were sampled at development stages I, II and III for proteomic analysis. Among the 1479 proteins detected on 2‐DE maps, 19, 70 and 69 spots in stages I, II and III, respectively, showed an at least twofold difference in volume between treatments and controls. Of these, 125 proteins were successfully identified and assigned to eight functional groups, chief among them are metabolism and energy, stress response, expression regulation and cytoskeleton proteins. Stress‐response proteins were predominantly down‐regulated in GA₃‐treated berries in stages I and II, and significantly up‐regulated in stage III. Up‐regulation of cytoskeleton, cell‐wall modification and other important proteins was found in the two latter stages of berry development. Our proteomic results and subsequent validation revealed, for the first time, the role of redox homeostasis in GA₃‐induced berry enlargement and markedly remodeled cellular protein expression in treated berries.     

Induction of Parthenocarpy in Rosa Canina and Diospyros Lotus by the application of growth regulators

The effect of indole-3-acetic acid (IAA) and gibberellic acid (GA₃) applications on parthenocarpic fruit set in Rosa canina and Diospyros lotus was investigated. GA₃ induced parthenocarpic fruit set in both plants, but IAA only in D. lotus. Maturation of seedless fruits was earlier than the seeded fruits. GA₃ caused a decrease in the fresh mass and size of both fruits. IAA induced an increase in the fresh mass and size in parthenocarpic fruit of D. lotus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Invertase activity and cell growth in lentil epicotyls

The activity of invertase and its relation to growth were studied in the epicotyls of lentil seedlings incubated in the presence and absence of gibberellic acid (GA₃).

Invertase activity per epicotyl increases relatively more rapidly than does length, reaches a maximum during most active elongation, and declines upon cessation of growth.

GA₃ enhances both growth and increase in invertase activity, without altering the kinetics of the 2 processes. If GA₃ is added during incubation invertase activity increases more rapidly than does elongation rate.

Incubation of the seedlings in solutions of polyethyleneglycol inhibits the increase of both growth and invertase activity, the latter actually undergoing a decline, but causes no great change in the relative effect of GA₃. In presence of polyethyleneglycol GA₃ has however a relatively greater effect on invertase activity than on growth.

Sugars in the incubation medium have no significant effect on growth and invertase activity in the epicotyl, except inhibition at relatively high concentrations.

Cycloheximide, actinomycin D, and 5-fluorodeoxyuridine (FUDR) inhibit both growth and the increase in invertase activity. Added during incubation cycloheximide causes complete inhibition of growth and a decrease in invertase activity with no appreciable lag phase. With actinomycin D and FUDR the inhibition occurs after lag periods of 2 to 3 and of at least 10 hours, respectively. Thus the increase in enzyme activity is very probably based on de-novo synthesis, and the enzyme is in a state of turnover during growth.

The enzyme is present in soluble form in the cytoplasm, not firmly bound to any cell structures.

     

Expression analysis of genes associated with sucrose accumulation in sugarcane under normal and GA<Subscript>3</Subscript>-induced source–sink perturbed conditions

Sugarcane accumulates high amount of sucrose, thus making it one of the important cash crops worldwide. The final destination of sucrose accumulation in sugarcane is sink tissue, i.e., stalk, supplied by the source, i.e., leaf, to fulfill the need of plant growth, respiration, storage, and other metabolic activities. Signals between sink and source tissues regulate sucrose accumulation in sink and possibly the negative feedback from the sink restrains further accumulation in the stalk. However, perturbation of this negative feedback may help to improve sugar yield. This can be achieved by the application of GA₃ (Gibberellic acid), a plant growth regulator, known to excite physiological responses and modify the source–sink metabolism through their effect on photosynthesis, which in turn improves sink strength by redistribution of the photoassimilates. In the present study, GA₃ applied canes showed prominent increase in invertase activity, at early stage of the application, to provide hexoses. This in turn helped increase the internodal length and cane capacity for additional accumulation of sucrose, thereby increasing sink strength. At maturity, sucrose% and brix% were found higher in middle and top portions of the GA₃-applied canes. Expression analysis of various sucrose metabolising genes viz., sucrose phosphate synthase (SPS), sucrose synthase (SuSy), soluble acid invertase, neutral invertase, and cell wall invertase (CWI) was carried out at different growth stages, using quantitative RT-PCR. CWI, which plays key role in phloem unloading in sink tissues, exhibited higher expression in GA₃ samples at the elongation stage which decreased with maturity, whereas both SuSy and SPS, involved in regulation of sucrose accumulation, showed a variable level of expression. Thus, GA₃ application on cane may improve the sucrose content in stalk and thus assuage maneuvering source–sink dynamics in sugarcane.     

Promotion of growth and invertase activity by gibberellic Acid in developing Avena internodes

Gibberellic acid (GA₃) induces invertase activity within 6 hours in Avena stem segments that are incubated in the dark at 23°. The maximum amount of promotion is about 5 times that of invertase activity in untreated segments. GA₃ causes significant promotion of invertase activity at concentrations as low as 3 × 10⁻⁵ μm GA₃. The increase in invertase activity elicited by GA₃ between 3 × 10⁻⁵ μm and 300 μm closely parallels the growth promotion that is caused by GA₃ over this concentration range. In control segments, invertase activity rises steeply during the first 6 hours of incubation, then decays slowly between 12 and 48 hours. In GA₃-treated segments, the invertase activity also rises during the first 6 hours, parallel to that in control segments and continues to rise during the next 42 hours. These changes in invertase activity during 48-hour incubation periods do not parallel the changes in growth that occur in control and GA₃-treated segments. Cycloheximide at 10 μg/ml abolishes all GA₃-promoted growth and invertase activity in these segments. Actinomycin D at 40 and 80 μg/ml decreases GA₃-promoted growth by 20% and invertase activity by 38 and 44%, respectively. The data clearly support the idea that protein synthesis is necessary for GA₃-promoted growth and invertase activity in Avena stem segments.     

Gibberellins and Abscisic Acid Promote Carbon Allocation in Roots and Berries of Grapevines

Carbon allocation within grapevines may affect berry growth and development. The plant hormones gibberellins (GAs) and abscisic acid (ABA) control various processes across the plant life and both have been involved in assimilate production and transport in different species. Hence, this work examined the distribution of sugars (sucrose, fructose, and glucose) and starch in grapevines at veraison after foliar applications of GA₃, ABA, and an inhibitor of GA biosynthesis, paclobutrazol (PBZ). The results demonstrated that GA₃ increased total grapevine mass, with carbon allocated to the whole grapevine (as structural and soluble carbohydrates). Both GA₃ and ABA increased monosaccharide (glucose and fructose) levels in berries (up to tenfold) and roots (up to threefold). However, GA₃ increased the net carbon fixation whereas ABA did not. PBZ diminished most growth parameters except grapevine mass, and allocated more carbohydrates to roots (up to threefold more sucrose and starch). Such results indicate that GAs promote net carbon fixation and transport, whereas ABA as a stress signal only enhances sugar transport; notwithstanding the two hormones promoted carbon allocation toward roots and berries.     

Effects of gibberellic Acid and gold light on germination, enzyme activities, and amino Acid pool size in a dwarf strain of watermelon

Gibberellic acid (GA₃) promotes and continuous gold light inhibits germination of seeds of a dwarf strain (WB-2) of watermelon [Citrullus lanatus (Thunb.) Matsu. and Nakai]. Osmotic inhibition of germination with mannitol in light-grown seeds of WB-2 was only slightly reversed by GA₃ at the concentrations used, whereas, GA₃ substantially relieved osmotic inhibition in dark-grown seeds.

The effects of GA₃ and gold light on development of catalase and invertase activities and on levels of free amino acids in germinating seeds of WB-2 were examined. Light depressed development of catalase and invertase activity. Levels of free amino acids increased more slowly in embryonic axes of light- than dark-incubated seeds, but in cotyledons higher levels of amino acids were maintained in light-grown seeds. GA₃ accelerated the development of catalase activity in whole embryos and invertase activity in embryonic axes, but did not significantly affect invertase activity in cotyledons during germination. GA₃ had little effect on amino acid pools in cotyledons and embryonic axes.

     

枣花芽分化过程中营养物质和内源激素含量及抗氧化酶活性变化研究

以新疆主栽品种灰枣和骏枣的花芽为材料,测定不同分化时期花芽的可溶性糖、还原糖、淀粉、可溶性蛋白含量,SOD、POD、PPO、CAT活性以及内源GA3、IAA、ABA、ZT水平的变化,并分析它们与花芽分化的关系,为枣花芽分化调控提供理论参考.结果表明:(1)灰枣和骏枣花芽可溶性糖、还原糖和淀粉含量在花芽分化过程的变化趋势...     

Effect of GA3, kinetin and indole acetic acid on carbohydrate metabolism in chickpea seedlings germinating under water stress

Enhanced amylase activity was observed during a 7-day-growth period in the cotyledons of PEG imposed water stressed chickpea seedlings grown in the presence of GA₃ and kinetin, when compared with stressed seedlings. During the first 5 days of seedling growth, the seedlings growing under water deficit conditions as well as those growing in the presence of PGRs had a higher amylase activity in shoots than that of control seedlings. Neither GA₃ nor kinetin increased the amylase activity of roots whereas IAA reduced root amylase activity. Activity of acid and alkaline invertases was maximum in shoots and at a minimum in cotyledons. Compared with alkaline invertase, acid invertase activity was higher in all the tissues. The reduced acid and alkaline invertase activities in shoots of stressed seedlings were enhanced by GA₃ and kinetin. Roots of stressed seedlings had higher alkaline invertase activity and GA₃ and IAA helped in bringing the level near to those in the controls. GA₃ and kinetin increased the sucrose synthase (SS) and sucrose phosphate synthase (SPS) activities in cotyledons of stressed seedlings, whereas they brought the elevated level of SPS of stressed roots to near normal level. The higher level of reducing sugars in the shoots of GA₃ and kinetin treated stressed seedlings could be due to the high acid invertase activity observed in the shoots, and the high level of bound fructose in the cotyledons of stressed seedlings could be due to the high activity of SPS in this tissue.     

Changes in Assimilated C Distribution and Soluble Acid Invertase Activity of Zinnia elegans Induced by Uniconazol, an Inhibitor of Gibberellin Biosynthesis

The physiological aspects involved in the Uniconazol-induced morphological changes in Zinnia elegans Jacq. cv Red Sun were clarified biochemically by determining the distribution of assimilated ¹³C as well as the soluble acid invertase activity. The application of Uniconazol, (E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-pentane-3-ol, reduced the growth of stems and leaves without affecting the roots. In addition, the translocation of assimilated ¹³C from leaf to other organs was inhibited, with the stem being more restricted than the root. These changes were matched by a corresponding decrease in the specific activity of soluble acid invertase. Subsequent treatment of GA₃ counteracted these effects of Uniconazol. Moreover, the total and reducing sugar content was closely correlated with the soluble acid invertase activity in the stem. It is concluded that the reduction in invertase activity of stem is a biochemical manifestation of the retardation of stem growth induced by Uniconazol.