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1.
Plants synthesize an astonishing diversity of isoprenoids, some of which play essential roles in photosynthesis, respiration,and the regulation of growth and development. Two independent pathways for the biosynthesis of isoprenoid precursors coexist within the plant cell: the cytosolic mevalonic acid (MVA) pathway and the plastidial methylerythritol phosphate (MEP)pathway. However, little is known about the effects of plant hormones on the regulation of these pathways. In the present study we investigated the effect of gibberellic acid (GA3) on changes in the amounts of many produced terpenoids and the activity of the key enzymes, 1-deoxy-D-xylulose 5-phosphate synthase (DXS) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), in these pathways. Our results showed GA3 caused a decrease in DXS activity in both sexes that it wasaccompanied by a decrease in chlorophylls, carotenoids and △9-tetrahydrocannabinol (THC) contents and an increase in α-tocopherol content. The treated plants with GA3 showed an increase in HMGR activity. This increase in HMGR activity was followed by accumulation of stigmasterol and β-sitosterol in male and female plants and campestrol in male plants.The pattern of the changes in the amounts of sterols was exactly similar to the changes in the HMGR activity. These data suggest that GA3 can probably influence the MEP and MVA pathways oppositely, with stimulatory and inhibitory effects on the produced primary terpenoids in MVA and DXS pathways, respectively. 相似文献
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Joan M. Malcolm Alan Crozier Colin G. N. Turnbull Einar Jensen 《Physiologia plantarum》1991,82(1):57-66
Gibberellin biosynthesis pathways were investigated using isotopically-labelled C19 - and C20 -gibberellins and cell-free preparations from immature seed of Phaseous coccineus cv. Prizewinner. The initial steps in an early 13-hydroxylation pathway involved the conversion gibberellin A12 -aldehyde (GA12 -aldehyde) to GA12 which was 13-hydroxylated to yield GA53 , Metabolism of GA53 yielded GA44 . In contrast to other cell-free systems, GA44 was not further converted, either as a δ-lactone or an open-lactone structure, to the C-20 aldehyde GA19 . GA19 was, however, metabolised to GA20 , GA5 and GA1 . GA20 represented a branch point in the pathway as it was converted both to GA1 , which was an end product, and GA5 which was further converted to GA6 . Like GA1 , GA6 was also an end-product of the early 13-hydroxylation pathway.
A non-13-hydroxylation pathway involving GA4 , GA15 , GA24 GA37 and GA36 also originated from GA12 . The terminal product of this pathway was the 3β-hydroxy C19 -gibberellin, GA4 . 相似文献
A non-13-hydroxylation pathway involving GA
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Wen-Shaw Chen Ho-Yih Liu Zin-Huang Liu Leuan Yang Wen-Huei Chen 《Physiologia plantarum》1994,90(2):391-395
When Phalaenopsis amabilis is grown under high temperature (30/25°C, day/night), flowering is blocked, and this can be reversed by gibberellin A3 (GA3 ) treatment. Associated with GA3 treatment under high temperature are increases in sucrose, glucose and fructose as compared with warm-treated plants. Spraying with sucrose solution alone caused leaf epinasty in plants grown under high temperature. Epinasty was released by about 9 days of GA3 treatment. In GA3 -treated plants under high temperatures, sucrose application to the source leaves led to an increase in sugar content in both leaves and inflorescence. In contrast, although in warm-treated plants sucrose application to the source leaves increased sugar content in the leaves, it did not increase sucrose content in the inflorescence. These results corroborate our hypothesis that in Phalaenopsis GA3 stimulates sink activity in the apical meristem and promotes the translocation of sucrose from source leaves to the apex of the inflorescence, where it accumulates. GA3 treatment led to an increase in sucrose synthase activity and had no effect on invertase activity. 相似文献
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The highly active, polar gibberellin-like substance found in the apical region of shoots of tall (genotype Le ) peas ( Pisum sativum L.) is shown by combined gas chromatography-mass spectrometry (GC/MS) to be GA1 . This substance is either absent or present at only low levels in dwarf ( le ) plants. Multiple ion monitoring (MIM) tentatively suggests that GA8 may also be present in shoot tissue of tall peas. Gibberellin A1 is the first 3 β-hydroxylated gibberellin positively identified in peas, and its presence in shoot tissue demonstrates the organ specificity of gibberellin production since GA1 has not been detected in developing seeds. Application of GA1 can mask the Le/le gene difference. However, whilst Le plants respond equally to GA20 and GA1 , le plants respond only weakly to GA20 , the major biologically active gibberellin found in dwarf peas. These results suggest that the Le gene controls the production of a 3 β-hydroxylase capable of converting GA20 to GA1 . Further support for this view comes from feeds of [3 H] GA20 to Le and le plants. Plants with Le metabolise [3 H] GA20 to three major products whilst le plants produce only one major product after the same time. The metabolite common to Le and le plants co-chromatographs with GA29 . The additional two metabolites in Le peas co-chromatograph with GA1 and GA8 . 相似文献
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The regulation by phytochrome of stem elongation in light-grown plants depends on gibberellins (GAs). To investigate whether this is mediated by a change in GA metabolism, the effect of the GA biosynthesis inhibitor LAB 198 999 (an acylcyclohexadione derivative) on the end-of-day far-red (FR) response in cowpea ( Vigna sinensis L.) epicotyl explants has been investigated. Growth of epicotyl explants of light-grown seedlings was enhanced when treated with far-red light before incubation in the dark (end-of-day FR effect). Low doses of LAB 198 999 (0.05 and 0.5 μg explant−1 ) reduced the effect of FR, whereas 5 to 50 μg explant−1 stimulated elongation of both red light (R)- and FR-treated epicotyl explants while nullifying the differences between R and FR treatments. In paclobutrazol-treated epicotyl explants, FR enhanced the response to applied GA1 and GA20 , whereas LAB 198 999 increased the activity of GA1 and decreased that of GA20 , [3 H]Gibberellin A1 , injected into the basal part of the epicotyl, was transported and metabolized mainly to [3 H]GA8 in the apical 20 mm of the epicotyl. The conversion of [3 H]GA1 to [3 H]GA8 was dramatically reduced by both end-of-day FR treatments and LAB 198 999 applications. In addition, both treatments enhanced epicotyl elongation. It is proposed that the regulation of cowpea epicotyl growth by phytocrome is mediated, at least partially, by modifying GA1 degradation. 相似文献
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After the application of [13 C3 H]-gibberellin A20 to wild-type (tall) sweet peas ( Lathyrus odoratus L.) labelled gibberellin A1 (GA1 ), GA8 , GA29 and 2-epiGA29 were identified as major metabolities by gas chromatography-mass spectrometry after high performance liquid chromatography. By contrast in genetically comparable dwarf ( II ) plants only labelled GA29 and 2-epiGA29 were produced in significant amounts, although evidence was obtained for trace amounts of labelled GA1 and GA8 . The apical portions of dwarf plants contained 8–10 times less GA1 than those of tall plants but at least as much GA20 (measured using di-deuterated internal standards). In conjunction with previous data these results strongly indicate that in genotype ll internode length is reduced and leaf growth altered by a reduction in GA1 levels attributable to a partial block in the 3β-hydroxylation of GA20 to GA1 .
In contrast to dwarf plants, semidwarf plants (genotype lblb ) contained more GA1 in the apical portion than wild-type counterparts. This is consistent with the suggestion that lb alters some aspect of GA sensitivity. 相似文献
In contrast to dwarf plants, semidwarf plants (genotype lblb ) contained more GA
10.
Evidence was obtained by gas chromatography-mass spectrometry and gas chromatography-selected ion monitoring for the presence of gibberellin A20 ), GA1 , GA29 , GA8 and 2-epiGA29 in vegetative shoots of tall sweet pea, Lathyrus odoratus L. Both tall (genotype L –) and dwarf (genotype II ) sweet peas elongated markedly in response to exogenous GA1 attaining similar internode lengths at the highest dose levels. Likewise internode length in both genotypes was reduced by application of the GA biosynthesis inhibitor, PP333. The ratio of leaflet length to width was reduced by application of PP333 to tall plants and this effect was reversed by GA1 . When applied to plants previously treated with PP333, GA20 promoted internode elongation of L – plants as effectively as GA1 , but GA29 was not as effective as GA1 when applied to II plants. In contrast, GA20 and GA1 were equally effective when applied to the semidwarf lb mutant but GA-treated lblb plants did not attain the same internode length as comparable GA-treated Lb – plants. The difference in stature between the tall and dwarf types persisted in dark-grown plants. It is concluded that GA1 may be important for internode elongation and leaf growth in sweet pea. Mutant l may influence GA1 synthesis by reducing 3β-hydroxylation of GA20 whereas mutant lb appears to affect GA sensitivity. 相似文献
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Jaime F. Martínez-García Cristina M. Santes José L. García-Martínez 《Physiologia plantarum》2000,108(4):426-434
It has been shown previously that gibberellins (GAs) mediate the phytochrome (Phy) control of cowpea ( Vigna sinensis L.) epicotyl elongation induced by end-of-day (EOD)-far-red light (FR). In the present work, the EOD-FR effect on GA metabolism and GA levels in cowpea has been investigated. GA1 , GA8 , GA19 and GA20 were identified in epicotyls, and GA1 , GA19 , GA20 and GA29 -catabolite in leaves of 6-day-old cowpea seedlings. The content of GA1 in the epicotyl paralleled the decrease of its growth rate, supporting the hypothesis that this is the GA bioactive in controlling cowpea epicotyl elongation. FR enhanced both the amount of [3H]GA1 in the epicotyl produced from applied [3H]GA20 , and that of applied [3H]GA1 that remained unmetabolized in epicotyl explants, suggesting that Phy may regulate the inactivation of GA1 . In agreement with this effect of light on GA1 metabolism, the contents of GA1 in the epicotyl remained higher in FR-treated than in R-treated explants. Moreover, in intact seedlings EOD-FR treatment increased both epicotyl elongation and GA1 content in the responsive epicotyl, whereas it was not altered in the leaves. These results show, for the first time, that photostable Phys modulate the stem elongation in light-grown plants by locally controlling the GA1 levels through regulation of its inactivation. 相似文献
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Four-week-old sunflower plants ( Helianthus annuus L. cv. Halcón), grown in different nutrient solutions, were used to study the effects of gibberellic acid (GA3 ) on K+ (Rb+ ) uptake by roots or transport to the shoot. Gibberellic acid application to the nutrient solution did not affect the exudation process of excised roots. When GA3 was sprayed on leaves 2 to 6 days before excising the roots, the rate of exudation and the K+ flux increased. When the exudation study was done keeping the roots in a nutrient solution in which Rb+ replaced K+ , the GA3 effects were evident also on Rb+ uptake and transport. In intact plants, GA3 increased the Rb+ transported to the shoot but did not affect Rb+ accumulation in the root. It is suggested that these GA3 effects can be explained if it is assumed that GA3 acts on the transport of ions to the xylem vessels. 相似文献
13.
Olavi Junttila 《Physiologia plantarum》1981,53(3):315-318
Fifteen different gibberellins (GA's) were tested for their ability to induce elongation growth under short day conditions in seedlings of Salix pentandra L. GA's were applied either to the apex or they were injected into a mature leaf. GA3 was highly active and also GA4+7 and GA4 showed high activity. GA1 , GA2 , GA5 , GA9 , GA13 , GA20 , GA36 and GA47 showed moderate activity. GA16 , GA17 , GA27 and GA41 exhibited low or no activity in doses up to 10 μg per plant. In general, a better growth response was obtained with an application to the apex than with an injection into the leaf. 相似文献
14.
Effect of plant growth hormones and polyamines on ornithine decarboxylase activity during the germination of barley seeds 总被引:1,自引:0,他引:1
Dimitrios A. Kyriakidis 《Physiologia plantarum》1983,57(4):499-504
Gibberellic acid (GA3 ) and β-indolylacetic acid (IAA), two of the well known growth hormones, induce four fold the activity of ornithine decarboxylase (ODC) during the germination of barley seeds ( Hordeum vulgare L. var. Beca). The optimal concentration for induction of ODC was 10–5 M for GA3 and 10–3 M for IAA. When 10–3 M of a polyamine, putrescine or spermidine, is added to the growth medium, ODC activity is significantly inhibited. This inhibition is due to the induction of a protein inhibitor of ODC (antizyme), whose apparent molecular weight is 16 000 ± 2 000 daltons. Addition of GA3 to cultures which have been grown for 50 or 98 h in the presence of polyamines, abolishes the observed inhibition of ODC activity, while in the reverse experiment, addition of polyamines at 50 or 98 h does not affect the ODC activity induced by GA3 . Cadaverine, a physiological plant diamine, enhances ODC activity; whereas 1,8-diaminooctane (the alkyl analogue of spermidine) does not have any effect. 相似文献
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Plants of Poa pratensis cv. Holt initiate inflorescence primordia when exposed to short days (SD) and low temperature, but require a secondary induction by at least 4 long days (LD) for further inflorescence development and stem elongation. Single or double applications of 10 µg per plant of gibberellins A1 , A3 , A5 and 16,17‐dihydro A5 (DHGA5 ) induced inflorescence development in a high proportion of plants in SD, but only if the plants were detillered to a single stem. Exposure to 2 LD cycles did not cause heading and flowering alone but enhanced the effect of exogenous gibberellins (GAs), bringing flowering to 100%. GA5 and DHGA5 were less effective than GA1 and GA3 in SD, especially with double applications, but were more effective than GA1 and GA3 when given together with 2 LD. The GAs had differential effects on vegetative growth and flowering, GA5 and DHGA5 causing much less leaf and stem growth than the other two GAs. Marginal induction, whether by LD or GA application, resulted in a high proportion of spikelets with viviparous proliferation. Thus, whereas GAs are inhibitory to the primary induction by SD, they can replace secondary induction by LD when vegetative growth is limited. 相似文献
16.
This work examined the effects of exogenously applied abscisic acid (ABA) on the content of chlorophyll, carotenoids, α-tocopherol,
squalene, phytosterols, Δ9-tetrahydrocannabinol (THC) concentration, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) and 1-deoxy-d-xylulose 5-phosphate synthase (DXS) activity in Cannabis sativa L. at flowering stage. Treatment with 1 and 10 mg l−1 ABA significantly decreased the contents of chlorophyll, carotenoids, squalene, stigmasterol, sitosterol, and HMGR activity
in female cannabis plants. ABA caused an increase in α-tocopherol content and DXS activity in leaves and THC concentration
in leaves and flowers of female plants. Chlorophyll content decreased with 10 mg l−1 ABA in male plants. Treatment with 1 and 10 mg l−1 ABA showed a decrease in HMGR activity, squalene, stigmasterol, and sitosterol contents in leaves but an increase in THC
content of leaves and flowers in male plants. The results suggest that ABA can induce biosynthesis of 2-methyl-d-erythritol-4-phosphate (MEP) pathway secondary metabolites accumulation (α-tocopherol and THC) and down regulated biosynthesis
of terpenoid primary metabolites from MEP and mevalonate (MVA) pathways (chlorophyll, carotenoids, and phytosterols) in Cannabis sativa. 相似文献
17.
The application of gibberellic acid (GA3 ,10 μ M ) as a root drench to 16-day-old plants of Phaseolus vulgaris L. cv. Masterpiece stimulated growth of the stem internodes and reduced root growth. GA3 treatment did not affect the export of 14 C from a primary leaf to which [14 C]-sucrose was applied, but greatly increased upward translocation to the elongation region of the stem at the expense of transport to the hypocotyl and root system. The observed changes in the patterns of growth and [14 C]-labelled assimilate distribution were correlated with an increase in the specific activity of acid invertase in the elongating stem internodes and a decrease in invertase activity in the hypocotyl and root. Sucrose concentration in the elongating internodes fell substantially after treatment with GA3 while the concentration of hexose sugars increased. We suggest that by stimulating acid invertase synthesis in the elongating internodes, GA3 acts to establish a more favourable sucrose gradient between these sinks and source leaves. Under source-limiting conditions this, in turn, will lead to a reduced rate of assimilate translocation to competing sinks in the root system. 相似文献
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Potato plants (Solanum tuberosum L. cv. Ostara) were grown in aerated water culture in a controlled environment. When the tubers had reached a diameter of 1–3 cm. 14 C-labelled or unlabelled gibberellic acid (GA3 ) was applied to the surface of the stolons at points approximately 1 crn from the developing tubers, and treatment continued for 10 days. - Significant quantities of GA3 moved into tuber tissue within 2–4 days of hormone application. This influx of GA3 was accompanied by a marked reduction in both the activity of ADPG-pyrophospharylase and the ratio ADPG-pyrophosphorylase/starch phosphorylase and an increase in the activity of UDPG-pyrophosphorylase. Starch phosphorylase activity initially increased slightly but then fell, whereas the activity of starch synthase remained constant throughout the experiment. The soluble sugar composition of the tubers changed qualitatively towards a pattern characteristic of growing stolon tips prior to tuber initiation, but there was no clear evidence of net starch degradation. Changes in the activities of the enzymes were observed prior to noticeable effects of the hormone on tuber growth rate or the development of new stolons at the tuber eyes. - GA3 - treated tubers imported more 14 C from labelled photosynthate than expected on the basis of growth rate. However, the capacity to convert solub#e-14 C to ethaTiol-insoluble-14 C (predominantly starch) was reduced in comparison with non-treated tubers. - The observed changes in carbohydrate composition and enzyme activities indicate that GA3 induces a drastic change in potato tuber metabolism towards a pattern characteristic for the termination of the storage process. 相似文献
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Endogenous gibberellins (GAs) in corms of Polianthes tuberosa L. (cv. Double) were isolated and identified by high performance liquid chromatography, bioassay and combined capillary gas chromatography-mass spectrometry (GC-MS). Gibberellins A1 , A19 , A20 and A53 were quantified at the vegetative, early floral initiation and flower development stages. The identification of 13-hydroxylated GAs indicates the presence of the early 13-hydroxylation pathway in P. tuberosa corms. An increase in GA1 and GA20 , and a decrease in GA19 levels, coincided with the transition from the vegetative phase to the stages of early floral initiation and flower development. GA53 stayed at constant levels at the 3 different growth stages. The absence of GA1 in vegetative corms and its presence in corms at early floral initiation and flower development stages suggest that GA1 is a causal factor in inducing floral initiation in P. tuberosa . When GA1 , GA3 , GA4 , GA20 and GA32 were applied to corms at the vegetative stage (plants about 5 cm in height), floral initiation was promoted by all of the GAs used, GA32 being the most active. In contrast with the other GAs, GA32 had no effect on stem elongation. Therefore, it is suggested that hydroxylated C-19 GAs play an important role in flower induction in P. tuberosa . 相似文献
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Spike lavender ( Lavandula latifolia ) essential oil is widely used in the perfume, cosmetic, flavouring and pharmaceutical industries. Thus, modifications of yield and composition of this essential oil by genetic engineering should have important scientific and commercial applications. We generated transgenic spike lavender plants expressing the Arabidopsis thaliana HMG1 cDNA, encoding the catalytic domain of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR1S), a key enzyme of the mevalonic acid (MVA) pathway. Transgenic T0 plants accumulated significantly more essential oil constituents as compared to controls (up to 2.1- and 1.8-fold in leaves and flowers, respectively). Enhanced expression of HMGR1S also increased the amount of the end-product sterols, β-sitosterol and stigmasterol (average differences of 1.8- and 1.9-fold, respectively), but did not affect the accumulation of carotenoids or chlorophylls. We also analysed T1 plants derived from self-pollinated seeds of T0 lines that flowered after growing for 2 years in the greenhouse. The increased levels of essential oil and sterols observed in the transgenic T0 plants were maintained in the progeny that inherited the HMG1 transgene. Our results demonstrate that genetic manipulation of the MVA pathway increases essential oil yield in spike lavender, suggesting a contribution for this cytosolic pathway to monoterpene and sesquiterpene biosynthesis in leaves and flowers of the species. 相似文献