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Gibberellins in seeds of Arabidopsis thaliana: biological activities,identification and effects of light and chilling on endogenous levels 总被引:4,自引:0,他引:4
The activities of several gibberellins in stimulating germination of wild-type and GA-deficient gal seeds of Arabidopsis thaliana were compared. Of the six compounds tested GA4 and GA7-isolactone had the highest activity and GA7 and GA9 the lowest; activities of GA1 and GA3 were intermediate. Combined application of pure GAs presented no indications that more than one GA receptor is involved. Four GAs were identified in extracts from wild-type and GA-insensitive gai seeds by combined gas chromatography mass spectrometry: GA1, GA3, GA4 and GA9. Effects of light and chilling on levels of GA1, GA4 and GA9 were studied using deuterated standards. Light increased both GA levels and germination in unchilled wild-type and gai seeds. As a result of irradiation GA levels in gai seeds were 7–10 times as high as in wild-type seeds. In the dark germination was 0%, in the light 14% of gai seeds and 95% of wild-type seeds germinated. A chilling pre-treatment of 7 days at 2°C was required to enhance further the germination of gai seeds in the light. Light did not increase GA levels of chilled seeds of either genotype; levels of GA4 and GA9 of chilled gai seeds, in the light were respectively 7 and 12 times lower than in non-chilled seeds, whereas the latter seeds germinated better. Slightly elevated levels of GA4 were detected in darkness after chilling, but germination capacity was still 0%. These results strengthened the conclusion that GAs are required for germination of A. thaliana seeds, whereby GA4 has intrinsic biological activity. However, it is unlikely that light and chilling stimulate germination primarily by increasing levels of GA. Instead GA sensitivity is a possible alternative. 相似文献
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The endogenous gibberellins (GAs) from shoots of the GA-insensitive mutant,gai, ofArabidopsis thaliana were analyzed and compared with the GAs from the Landsberg erecta (Ler) line. Twenty GAs were identified in Ler plants by
full-scan gas chromatography-mass spectrometry (GC-MS) and Kovats retention indices (KRI's). These GAs are members of the
early-13-hydroxylation pathway (GA53, GA44, GA19, GA17, GA20, GA1, GA29, and GA8), the non-3,13-hydroxylation pathway (GA12, GA15, GA24, GA25, GA9, and GA51), and the early-3-hydroxylation pathway (GA37, GA27, GA36, GA13, GA4, and GA34). The same GAs, except GA53, GA44, GA37, and GA29 were detected in thegai mutant by the same methods. In addition, extracts fromgai plants contained GA41 and GA71. Both lines also contained several unknown GAs. In Ler plants these were mainly hydroxy-GA12 derivatives, whereas in thegai mutant hydroxy-GA24, hydroxy-GA25, and hydroxy-GA9 compounds were detected. Quantification of seven GAs by GC-selected ion monitoring (SIM), using internal standards, and comparisons
of the ion intensities in the SIM chromatograms of the other thirteen GAs, demonstrated that thegai mutant had reduced levels of all C20-dicarboxylic acids (GA53, GA44, GA19, GA12, GA15, GA24, GA37, GA27, and GA36). In contrast,gai plants had increased levels of C20-tricarboxylic acid GAs (GA17, GA25, and GA41) and of all C19-GAs (GA20, GA1, GA8, GA9, GA51, GA4, GA34, and GA71) except GA29. The 3β-hydroxylated GAs, GA1 and GA4, and their respective 2β-hydroxylated derivatives, GA8 and GA34, were the most abundant GAs found in shoots of thegai mutant. Thus, thegai mutation inArabidopsis results in a phenotype that resembles GA-deficient mutants, is insensitive to both applied and endogenous GAs, and contains
low levels of C20-dicarboxylic acid GAs and high levels of C19-GAs. This indicates that theGAI gene controls a step beyond the synthesis of an active GA. Thegai mutant is presumably a GA-receptor mutant or a mutant with a block in the transduction pathway between the receptor and stem
elongation.
We thank Dr. L.N. Mander, Australian National University, Canberra, for providing [2H]gibberellins, Dr. B.O. Phinney, University of California, Los Angeles, USA for [13C]GA8, and Dr. D.A. Gage, MSU-NIH Mass Spectrometry Facility (grant No. DRR00480), for advice with mass spectrometry. This work
was supported by a fellowship from the Spanish Ministry of Agriculture (I.N.I.A.) to M.T., by the U.S. Department of Energy
under Contract DE-ACO2-76ERO-1338, and by U.S. Department of Agriculture grant No. 88-37261-3434 to J.A.D.Z. 相似文献
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Over-expression of a tobacco homeobox gene,
NTH15
, decreases the expression of a gibberellin biosynthetic gene encoding GA 20-oxidase 总被引:9,自引:3,他引:6
Miyako Tanaka-Ueguchi Hironori Itoh Naomi Oyama Masaji Koshioka Makoto Matsuoka 《The Plant journal : for cell and molecular biology》1998,15(3):391-400
Ectopic expression of the homeobox gene, NTH15 ( Nicotiana tabacum homeobox 15) in transgenic tobacco leads to abnormal leaf and flower morphology, accompanied by a decrease in the content of the active gibberellin, GA1. Quantitative analysis of intermediates in the GA biosynthetic pathway revealed that the step from GA19 to GA20 was blocked in transgenic tobacco plants overexpressing NTH15 . To investigate the relationship between the expression of NTH15 and genes involved in GA biosynthesis, we isolated three cDNA clones from tobacco encoding two types of GA 20-oxidase and a 3β-hydroxylase. RNA gel blot analysis revealed that the expression of one gene ( Ntc12 , encoding GA 20-oxidase), which in wild-type tobacco plants was abundantly expressed in leaves, was strongly suppressed in the transformants. The expression level of Ntc12 decreased with increasing severity of phenotype of transgenic tobacco leaves. The abnormal leaf morphology was largely overcome by treatment with GA20 or GA1 but not by GA19. These data strongly suggest that overexpression of NTH15 inhibits the expression of Ntc12 , resulting in reduced levels of active GA and abnormal leaf morphology in transgenic tobacco plants. In situ hybridization in wild-type tobacco revealed that expression of Ntc12 occurred mainly in the rib meristem, cells surrounding the procambium and in leaf primordia. Expression was not seen in the tunica, corpus and procambium, tissues in which NTH15 was predominantly expressed. The contrasting expression patterns of these genes may reflect their antagonistic functions in the formation of lateral organs from the shoot apical meristem. 相似文献
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The semi-dominant gai mutation of arabidopsis confers a dark-green dwarf phenotype resembling that of gibberellin (GA)-deficient mutants. In contrast to GA-deficient mutants, gai mutants do not respond to GA treatments and accumulate higher levels of bioactive GAs than are found in wild-type controls. The gai mutation thus alters the responses of plant cells to GA, indicating that the GAI (wild-type) gene product is involved in GA reception and/or signal transduction. Here we describe the isolation and preliminary characterization of a mutation, gas1-1, which is not linked to gai and which partially suppresses the effect of the gai mutation. Double mutant, gai gas1-1, homozygotes are less severely dwarfed and lighter green than gai GAS1 controls. However, comparisons of the effects of treatments with exogenous GA demonstrate that gas1-1 does not increase the GA responsiveness of the gai mutant. Thus the gas1-1 mutation appears to reduce the GA-dependency of plant growth, and identifies a gene (GAS1) whose product is a candidate GA signal-transduction component.Abbreviations GA
gibberellin
- GA3
gibberellic acid
We thank Maarten Koornneef (Wageningen Agricultural University, The Netherlands) for providing mutant seed stocks; Mark Aarts and Bernard Mulligan (University of Nottingham, UK) for performing the -irradiation. This work was made possible by AFRC/BBSRC PMB Grants PG208/520 and PG208/0600, and by a grant from the Gatsby Charitable Foundation. P.C. was supported by a Human Capital and Mobility Fellowship from the EC. 相似文献
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Tianxiu Zhong Lijuan Zhang Shanshan Sun Huiming Zeng Liebao Han 《Plant biotechnology reports》2014,8(5):399-408
Drought resistance is increased in plants by the absence of the hormone gibberellic acid (GA) or by a lack of GA sensitivity. We studied the effects of tissue-specific reduction in GA levels on drought tolerance, on recovery from drought stress, and on primary and secondary growth using transgenic tobacco plants expressing the GA-inactivating gene PtGA2ox 1 (GA 2-oxidase) specifically in leaves, stems, or roots. Localized reduction of bioactive GA1 levels was achieved by tissue-specific expression of the PtGA2ox 1 gene in leaves using the rbcs promoter (LD plants), in roots using the TobRB7 promoter (RD plants), and in stems using the LMX5 promoter (SD plants). In response to drought stress, all transgenic tobacco plants exhibited reduced primary and secondary growth and increased drought tolerance with a corresponding reduction in malondialdehyde levels, higher relative water content, increased proline and sugar content, and elevated peroxidase, superoxide dismutase, and catalase activities relative to wild-type plants. The highest level of drought tolerance and the most rapid recovery from stress was achieved by localized reduction of GA1 in the roots of the RD transgenic plants. In addition, although the total bioactive GA1 content in RD and LD plants was essentially identical, the heights of LD plants were significantly greater and drought tolerance was significantly less than in RD plants. It is possible that the site of gibberellin-related gene expression plays an important role in the balance between growth and drought tolerance. 相似文献
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Overexpression of 20-Oxidase Confers a Gibberellin-Overproduction
Phenotype in Arabidopsis 总被引:6,自引:0,他引:6
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Shihshieh Huang Anuradha S. Raman Joel E. Ream Hideji Fujiwara R. Eric Cerny Sherri M. Brown 《Plant physiology》1998,118(3):773-781
In the gibberellin (GA) biosynthesis pathway, 20-oxidase catalyzes the oxidation and elimination of carbon-20 to give rise to C19-GAs. All bioactive GAs are C19-GAs. We have overexpressed a cDNA encoding 20-oxidase isolated from Arabidopsis seedlings in transgenic Arabidopsis plants. These transgenic plants display a phenotype that may be attributed to the overproduction of GA. The phenotype includes a longer hypocotyl, lighter-green leaves, increased stem elongation, earlier flowering, and decreased seed dormancy. However, the fertility of the transgenic plants is not affected. Increased levels of endogenous GA1, GA9, and GA20 were detected in seedlings of the transgenic line examined. GA4, which is thought to be the predominantly active GA in Arabidopsis, was not present at increased levels in this line. These results suggest that the overexpression of this 20-oxidase increases the levels of some endogenous GAs in transgenic seedlings, which causes the GA-overproduction phenotype. 相似文献
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Gibberellin (GA) is a classical plant hormone involved in many aspects of plant growth and development. A family of five homologs called the DELLA proteins, comprised of GAI, RGA, RGL1, RGL2 and RGL3, were recently found to act as critical GA signal mediators in Arabidopsis. Reports have shown that GAI and RGA are coupled together to repress stem elongation growth whereas RGL2 is a major negative regulator of seed germination. GA down-regulates DELLA proteins through protein degradation likely via the proteasome pathway. The conserved and functionally important DELLA domain is responsible for protein stability in response to GA. 相似文献
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CONSTITUTIVE PHOTOMORPHOGENIC 1 promotes seed germination by destabilizing RGA-LIKE 2 in Arabidopsis
Byoung-Doo Lee Yehyun Yim Esther Caibano Suk-Hwan Kim Marta García-Len Vicente Rubio Sandra Fonseca Nam-Chon Paek 《Plant physiology》2022,189(3):1662
Under favorable moisture, temperature, and light conditions, gibberellin (GA) biosynthesis is induced and triggers seed germination. A major mechanism by which GA promotes seed germination is by promoting the degradation of the DELLA protein RGA-LIKE 2 (RGL2), a major repressor of germination in Arabidopsis (Arabidopsis thaliana) seeds. Analysis of seed germination phenotypes of constitutive photomorphogenic 1 (cop1) mutants and complemented COP1-OX/cop1-4 lines in response to GA and paclobutrazol (PAC) suggested a positive role for COP1 in seed germination and a relation with GA signaling. cop1-4 mutant seeds showed PAC hypersensitivity, but transformation with a COP1 overexpression construct rendered them PAC insensitive, with a phenotype similar to that of rgl2 mutant (rgl2-SK54) seeds. Furthermore, cop1-4 rgl2-SK54 double mutants showed a PAC-insensitive germination phenotype like that of rgl2-SK54, identifying COP1 as an upstream negative regulator of RGL2. COP1 interacted directly with RGL2, and in vivo this interaction was strongly enhanced by SUPPRESSOR OF PHYA-105 1. COP1 directly ubiquitinated RGL2 to promote its degradation. Moreover, GA stabilized COP1 with consequent RGL2 destabilization. By uncovering this COP1–RGL2 regulatory module, we reveal a mechanism whereby COP1 positively regulates seed germination and controls the expression of germination-promoting genes.A master regulator of photomorphogenesis positively regulates germination in Arabidopsis seeds by directly ubiquitinating and promoting the degradation of a key repressor of seed germination. 相似文献
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Xingshan Jiang Heying Li Changlian Peng Haiyang Wang Hong Wu Xiaojing Wang 《The Plant journal : for cell and molecular biology》2012,72(5):768-780
Chloroplast biogenesis needs to be well coordinated with cell division and cell expansion during plant growth and development to achieve optimal photosynthesis rates. Previous studies showed that gibberellins (GAs) regulate many important plant developmental processes, including cell division and cell expansion. However, the relationship between chloroplast biogenesis with cell division and cell expansion, and how GA coordinately regulates these processes, remains poorly understood. In this study, we showed that chloroplast division was significantly reduced in the GA‐deficient mutants of Arabidopsis (ga1‐3) and Oryza sativa (d18‐AD), accompanied by the reduced expression of several chloroplast division‐related genes. However, the chloroplasts of both mutants exhibited increased grana stacking compared with their respective wild‐type plants, suggesting that there might be a compensation mechanism linking chloroplast division and grana stacking. A time‐course analysis showed that cell expansion‐related genes tended to be upregulated earlier and more significantly than the genes related to chloroplast division and cell division in GA‐treated ga1‐3 leaves, suggesting the possibility that GA may promote chloroplast division indirectly through impacting leaf mesophyll cell expansion. Furthermore, our cellular and molecular analysis of the GA‐response signaling mutants suggest that RGA and GAI are the major repressors regulating GA‐induced chloroplast division, but other DELLA proteins (RGL1, RGL2 and RGL3) also play a role in repressing chloroplast division in Arabidopsis. Taken together, our data show that GA plays a critical role in controlling and coordinating cell division, cell expansion and chloroplast biogenesis through influencing the DELLA protein family in both dicot and monocot plant species. 相似文献
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Gibberellin (GA) 2-oxidases play an important role in the GA catabolic pathway through 2β-hydroxylation. There are two classes of GA2oxs, i.e., a larger class of C19-GA2oxs and a smaller class of C20-GA2oxs. In this study, the gene encoding a GA 2-oxidase of rice, Oryza sativa GA 2-oxidase 5 (OsGA2ox5), was cloned and characterized. BLASTP analysis showed that OsGA2ox5 belongs to the C20-GA2oxs subfamily, a subfamily of GA2oxs acting on C20-GAs (GA12, GA53). Subcellular localization of OsGA2ox5-YFP in transiently transformed onion epidermal cells revealed the presence of this protein in both of the nucleus and cytoplasm. Real-time PCR analysis, along with GUS staining, revealed that OsGA2ox5 is expressed in the roots, culms, leaves, sheaths and panicles of rice. Rice plants overexpressing OsGA2ox5 exhibited dominant dwarf and GA-deficient phenotypes, with shorter stems and later development of reproductive organs than the wild type. The dwarfism phenotype was partially rescued by the application of exogenous GA3 at a concentration of 10 µM. Ectopic expression of OsGA2ox5 cDNA in Arabidopsis resulted in a similar phenotype. Real-time PCR assays revealed that both GA synthesis-related genes and GA signaling genes were expressed at higher levels in transgenic rice plants than in wild-type rice; OsGA3ox1, which encodes a key enzyme in the last step of the bioactive GAs synthesis pathway, was highly expressed in transgenic rice. The roots of OsGA2ox5-ox plants exhibited increased starch granule accumulation and gravity responses, revealing a role for GA in root starch granule development and gravity responses. Furthermore, rice and Arabidopsis plants overexpressing OsGA2ox5 were more resistant to high-salinity stress than wild-type plants. These results suggest that OsGA2ox5 plays important roles in GAs homeostasis, development, gravity responses and stress tolerance in rice. 相似文献
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Alteration of Hormone Levels in Transgenic Tobacco Plants
Overexpressing the Rice Homeobox Gene OSH1 总被引:8,自引:0,他引:8
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Shinnosuke Kusaba Yuriko Kano-Murakami Makoto Matsuoka Masanori Tamaoki Tomoaki Sakamoto Isomaro Yamaguchi Masashi Fukumoto 《Plant physiology》1998,116(2):471-476
The rice (Oryza sativa L.) homeobox gene OSH1 causes morphological alterations when ectopically expressed in transgenic rice, Arabidopsis thaliana, and tobacco (Nicotiana tabacum L.) and is therefore believed to function as a morphological regulator gene. To determine the relationship between OSH1 expression and morphological alterations, we analyzed the changes in hormone levels in transgenic tobacco plants exhibiting abnormal morphology. Levels of the plant hormones indole-3-acetic acid, abscisic acid, gibberellin (GA), and cytokinin (zeatin and trans-zeatin [Z]) were measured in leaves of OSH1-transformed and wild-type tobacco. Altered plant morphology was found to correlate with changes in hormone levels. The more severe the alteration in phenotype of transgenic tobacco, the greater were the changes in endogenous hormone levels. Overall, GA1 and GA4 levels decreased and abscisic acid levels increased compared with wild-type plants. Moreover, in the transformants, Z (active form of cytokinin) levels were higher and the ratio of Z to Z riboside (inactive form) also increased. When GA3 was supplied to the shoot apex of transformants, internode extension was restored and normal leaf morphology was also partially restored. However, such GA3-treated plants still exhibited some morphological abnormalities compared with wild-type plants. Based on these data, we propose the hypothesis that OSH1 affects plant hormone metabolism either directly or indirectly and thereby causes changes in plant development. 相似文献
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Decreased GA1 Content Caused by the Overexpression of
OSH1 Is Accompanied by Suppression of GA
20-Oxidase Gene Expression 总被引:3,自引:0,他引:3
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Shinnosuke Kusaba Masashi Fukumoto Chikako Honda Isomaro Yamaguchi Tomoaki Sakamoto Yuriko Kano-Murakami 《Plant physiology》1998,117(4):1179-1184
We previously reported that overexpression of the rice homeobox gene OSH1 led to altered morphology and hormone levels in transgenic tobacco (Nicotiana tabacum L.) plants. Among the hormones whose levels were changed, GA1 was dramatically reduced. Here we report the results of our analysis on the regulatory mechanism(s) of OSH1 on GA metabolism. GA53 and GA20, precursors of GA1, were applied separately to transgenic tobacco plants exhibiting severely changed morphology due to overexpression of OSH1. Only treatment with the end product of GA 20-oxidase, GA20, resulted in a striking promotion of stem elongation in transgenic tobacco plants. The internal GA1 and GA20 contents in OSH1-transformed tobacco were dramatically reduced compared with those of wild-type plants, whereas the level of GA19, a mid-product of GA 20-oxidase, was 25% of the wild-type level. We have isolated a cDNA encoding a putative tobacco GA 20-oxidase, which is mainly expressed in vegetative stem tissue. RNA-blot analysis revealed that GA 20-oxidase gene expression was suppressed in stem tissue of OSH1-transformed tobacco plants. Based on these results, we conclude that overexpression of OSH1 causes a reduction of the level of GA1 by suppressing GA 20-oxidase expression. 相似文献
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Recognizing the physiological diversity of different plant organs, studies were conducted to investigate the distribution of endogenous gibberellins (GAs) in Brassica (canola or oilseed rape). GA1 and its biosynthetic precursors, GA20 and GA19, were extracted, chromatographically purified, and quantified by gas-chromatography-selected ion monitoring (GC-SIM), using [2H2]GAs as internal standards. In young (vegetative) B. napus cv. Westar plants, GA concentrations were lowest in the roots, increased acropetally along the shoot axis, and were highest in the shoot tips. GA concentrations were high but variable in leaves. GA1 concentrations also increased acropetally along the plant axis in reproductive plants. During early silique filling, GA1 concentrations were highest in siliques and progressively lower in flowers, inflorescence stalks (peduncles plus pedicels), stem, leaves, and roots. Concentrations of GA19 and GA20 showed similar patterns of distribution except in leaves, in which concentrations were higher, but variable. Immature siliques were qualitatively rich in endogenous GAs and GA1, GA3, GA4, GA8, GA9, GA17, GA19, GA20, GA24, GA29, GA34, GA51, and GA53 were identified by GC-SIM. In whole siliques, GA19, GA20, GA1, and GA8 concentrations declined during maturation due to declining levels in the maturing seeds; their concentrations in the silique coats remained relatively constant and low. These studies demonstrate that GAs are differentially distributed in Brassica with a general pattern of acropetally increasing concentration in shoots and high concentration in actively growing and developing organs. 相似文献
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Zheng Xiao Ruipeng Fu Jiyuan Li Zhengqi Fan Hengfu Yin 《Plant Molecular Biology Reporter》2016,34(1):182-191