赤霉素调节植物对非生物逆境的耐性

赤霉素（GAs）是一类重要的植物激素,调控植物生长发育的诸多方面．最近的研究表明,GA也参与对生物与非生物胁迫的响应,然而GA参与非生物胁迫响应的遗传学证据及其机制有待于进一步研究．本实验室前期研究证明,水稻EullfELONGATEDUPPERMOSTINTERNODE）通过一个新的生化途径降解体内的活性赤霉素分子,并参与调控水稻对病原菌的基础抗病性．本研究发现,euil突变体对盐胁迫能力降低,而超表达EUll基因的水稻和拟南芥耐盐性显著提高．进一步研究发现,积累高含量赤霉素的水稻euil突变体对脱落酸（ABA）的敏感性下降,而赤霉素缺失的EUll超表达转基因水稻和拟南芥均改变了对于ABA的敏感性．EUll基因的转录受逆境诱导,其功能缺失与超表达调控了逆境标志基因的表达．综上推测,GA可能是通过影响ABA的信号途径从而改变了植物对非生物胁迫的响应．     

Gibberellins are required for seed development and pollen tube growth in Arabidopsis

Gibberellins (GAs) are tetracyclic diterpenoids that are essential endogenous regulators of plant growth and development. GA levels within the plant are regulated by a homeostatic mechanism that includes changes in the expression of a family of GA-inactivating enzymes known as GA 2-oxidases. Ectopic expression of a pea GA 2-oxidase2 cDNA caused seed abortion in Arabidopsis, extending and confirming previous observations obtained with GA-deficient mutants of pea, suggesting that GAs have an essential role in seed development. A new physiological role for GAs in pollen tube growth in vivo also has been identified. The growth of pollen tubes carrying the 35S:2ox2 transgene was reduced relative to that of nontransgenic pollen, and this phenotype could be reversed partially by GA application in vitro or by combining with spy-5, a mutation that increases GA response. Treatment of wild-type pollen tubes with an inhibitor of GA biosynthesis in vitro also suggested that GAs are required for normal pollen tube growth. These results extend the known physiological roles of GAs in Arabidopsis development and suggest that GAs are required for normal pollen tube growth, a physiological role for GAs that has not been established previously.     

Long-distance transport of endogenous gibberellins in Arabidopsis

Gibberellins (GAs) are phytohormones controlling major aspects of plant growth and development. Although previous studies suggested the existence of a transport of GAs in plants, the nature and properties associated with this transport were unknown. We recently showed through micrografting and biochemical approaches that the GA₁₂ precursor is the chemical form of GA undergoing long-distance transport across plant organs in Arabidopsis. Endogenous GA₁₂ moves through the plant vascular system from production sites to recipient tissues, in which GA₁₂ can be converted to bioactive forms to support growth via the activation of GA-dependent processes. GAs are also essential to promote seed germination; hence GA biosynthesis mutants do not germinate without exogenous GA treatment. Our results suggest that endogenous GAs are not (or not sufficiently) transmitted to the offspring to successfully complete the germination under permissive conditions.     

Cytochromes P450 in gibberellin biosynthesis

The gibberellins (GAs) are an important class of plant growth regulators that are active in many aspects of plant growth and development. GAs are synthesized by a complex pathway involving three enzyme classes spanning different subcellular compartments. One of these enzyme classes is the cytochrome P450s which catalyze a number of oxidation steps in the middle part of the pathway. Mutants in these cytochrome P450-mediated steps in a number of species have been crucial in isolating the genes encoding these enzymes and have also played an important role in understanding GA physiology. GAs are also synthesized by fungi, in a biosynthesis pathway largely catalyzed by cytochrome P450s. The fungal pathway appears to have evolved independently to that of higher plants.

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Practical Applications of Manipulating Plant Architecture by Regulating Gibberellin Metabolism

The international trade in floriculture is estimated to be worth about US$150 billion, with the global demand for ornamentals steadily increasing. Consumer choice is influenced by factors such as plant architecture and flower colour. Conventional breeding has been responsible for the introduction of novel traits into ornamental plants and has played an important role in the development of new cultivars. However, a restricted gene pool and failure of distant crosses have led to the exploitation of somatic cell techniques, particularly genetic transformation, to generate plants with desirable traits. Gibberellins (GAs) are endogenous plant hormones that control key aspects of growth and development. Chemical growth regulators that modify GA biosynthesis are used extensively in horticulture to control plant stature, increasing production costs, manpower, and environmental risks. An alternative strategy involves genetic manipulation of GA metabolism to induce phenotypic changes, particularly alteration of stature. Because ornamentals are not used for human consumption, genetic manipulation approaches with these plants may be more acceptable in the immediate future to the general public, in certain parts of the world, than genetically manipulated food crops.     

异戊二烯类植物激素赤霉素和脱落酸的代谢调控

赤霉素和脱落酸在植物生理过程中具有重要的调控作用,其生物合成途径迄今已基本阐明。赤霉素与类胡萝卜素的生物合成途径具有共同前体牻牛儿基牻牛儿基二磷酸,而脱落酸则直接来自于类胡萝卜素。参与这两种植物激素和类胡萝卜素代谢过程的大多数酶基因已经从不同植物中获得克隆;各种调控方式也随着分子生物学的研究工作而得到鉴定。本文就近年来对赤霉素和脱落酸等代谢调控机制及其与植物类胡萝卜素代谢之间关系的研究工作做简要回顾。     

赤霉素解除木本植物季节性休眠机制的研究进展

赤霉素是一种高效能的广谱植物生长调节剂,能够促进植物的生长发育,具有重要的生物学功能。该文主要对国内外近年来有关赤霉素在木本植物季节性休眠解除中的应用、赤霉素解除木本植物季节性休眠的生理机制、赤霉素代谢相关基因在木本植物季节性休眠中的作用以及赤霉素解除木本植物季节性休眠的分子机制等方面的研究进展进行综述,同时对下一步的研究方向进行了展望,以期能够更好地阐述赤霉素解除木本植物季节性休眠的分子机制,为赤霉素在木本植物季节性休眠解除中的应用提供理论依据。     

Evolutionarilv Conserved DELLA-mediated Gibberellin Signaling in Plants

Gibberellins (GAs) play important roles in many essential plant growth and development processes. A family of nuclear growth-repressing DELLA proteins is the key component in GA signaling. GA perception is mediated by GID1, and the key event of GA signaling is the degradation of DELLA proteins via the 26S proteasome pathway. DELLA proteins integrating other plant hormones signaling and environmental cue modulating plant growth and development have been revealed. GA turning on the de-DELLA-repressing system is conserved, and independently establishes step-by-step recruitment of GAstimulated GID1-DELLA interaction and DELLA growth-repression functions during land plant evolution. These discoveries open new prospects for the understanding of GA action and DELLA-mediated signaling in plants.     

Evolutionarily conserved DELLA-mediated gibberellin signaling in plants

Gibberellins (GAs) play important roles in many essential plant growth and development processes. A family of nuclear growth-repressing DELLA proteins is the key component in GA signaling. GA perception is mediated by GID1, and the key event of GA signaling is the degradation of DELLA proteins via the 26S proteasome pathway. DELLA proteins integrating other plant hormones signaling and environmental cue modulating plant growth and development have been revealed. GA turning on the de-DELLA-repressing system is conserved, and independently establishes step-by-step recruitment of GA-stimulated GID1-DELLA interaction and DELLA growth-repression functions during land plant evolution. These discoveries open new prospects for the understanding of GA action and DELLA-mediated signaling in plants.     

The gar2 and rga alleles increase the growth of gibberellin-deficient pollen tubes in Arabidopsis

Ectopic expression in Arabidopsis of a pea (Pisum sativum) cDNA (2ox2) encoding a gibberellin (GA) 2-oxidase (PsGA2ox2), involved in the deactivation of biologically active GAs, has been used to establish a role for GAs in promoting pollen tube growth. One line, 35S:2ox2/28c, when homozygous for the transgene, exhibits a novel small fruit phenotype. The 28c transgene reduces pollen tube growth, and this results in a reduced number of fertilized seeds that are only present at the end of the silique nearest the stigma. To confirm that the 28c pollen tube phenotype is due to sense expression of the 2ox2 mRNA, a “hairpin” RNA interface silencing construct, designed to silence 2ox2 expression, has been used to restore pollen tube growth and fruit development. The interaction between 28c and other mutants with increased GA response has also been examined to provide further evidence that GAs play an important role in pollen tube growth. Based on the ability of mutant alleles to suppress the 35S:2ox2/28c phenotype, we define new roles for the gar2-1 and rga alleles in GA signaling during pollen tube elongation in addition to their previously established roles in vegetative tissues. In contrast to the constitutive GA response observed in internodes and leaves lacking RGA and GAI, the rga-2 gai-d5 mutant combination is only a partial suppressor of the 28c phenotype. Because the dominant dwarfing gai-1 allele reduces GA response in vegetative tissues, its effect on plant fertility has been examined. Although gai-1 reduces seed set, this appears to reflect defects in reproductive development other than pollen tube function. Finally, we show that the genetic background (Landsberg erecta or Columbia) modifies the 28c phenotype and that this effect is not due to the ER/er difference between these two ecotypes.     

Altered Expression of SPINDLY Affects Gibberellin Response and Plant Development

Gibberellins (GAs) are plant hormones with diverse roles in plant growth and development. SPINDLY (SPY) is one of several genes identified in Arabidopsis that are involved in GA response and it is thought to encode an O-GlcNAc transferase. Genetic analysis suggests that SPY negatively regulates GA response. To test the hypothesis that SPY acts specifically as a negatively acting component of GA signal transduction, spy mutants and plants containing a 35S:SPY construct have been examined. A detailed investigation of the spy mutant phenotype suggests that SPY may play a role in plant development beyond its role in GA signaling. Consistent with this suggestion, the analysis of spy er plants suggests that the ERECTA (ER) gene, which has not been implicated as having a role in GA signaling, appears to enhance the non-GA spy mutant phenotypes. Arabidopsis plants containing a 35S:SPY construct possess reduced GA response at seed germination, but also possess phenotypes consistent with increased GA response, although not identical to spy mutants, during later vegetative and reproductive development. Based on these results, the hypothesis that SPY is specific for GA signaling is rejected. Instead, it is proposed that SPY is a negative regulator of GA response that has additional roles in plant development.     

Gibberellic acid in plant: Still a mystery unresolved

Gibberellic acid (GA), a plant hormone stimulating plant growth and development, is a tetracyclic di-terpenoid compound. GAs stimulate seed germination, trigger transitions from meristem to shoot growth, juvenile to adult leaf stage, vegetative to flowering, determines sex expression and grain development along with an interaction of different environmental factors viz., light, temperature and water. The major site of bioactive GA is stamens that influence male flower production and pedicel growth. However, this opens up the question of how female flowers regulate growth and development, since regulatory mechanisms/organs other than those in male flowers are mandatory. Although GAs are thought to act occasionally like paracrine signals do, it is still a mystery to understand the GA biosynthesis and its movement. It has not yet confirmed the appropriate site of bioactive GA in plants or which tissues targeted by bioactive GAs to initiate their action. Presently, it is a great challenge for scientific community to understand the appropriate mechanism of GA movement in plant’s growth, floral development, sex expression, grain development and seed germination. The appropriate elucidation of GA transport mechanism is essential for the survival of plant species and successful crop production.     

Engineering and genetic approaches to modulating the glutathione network in plants

Reduced glutathione (GSH) is the most abundant low-molecular weight thiol in plant cells. It accumulates to high concentrations, particularly in stress situations. Because the pathway of GSH synthesis consists of only two enzymes, manipulation of cellular glutathione contents by genetic intervention has proved to be relatively straightforward. The discovery of a new bacterial bifunctional enzyme catalysing GSH synthesis but lacking feedback inhibition characteristics offers new prospects of enhancing GSH production and accumulation by plant cells, while the identification of γ-glutamyl cysteine and glutathione transporters provides additional possibilities for selective compartment-specific targeting. Such manipulations might also be used to affect plant biology in disparate ways, because GSH and glutathione disulphide (GSSG) have crucial roles in processes as diverse as the regulation of the cell cycle, systemic acquired resistance and xenobiotic detoxification. For example, depletion of the total glutathione pool can be used to manipulate the shoot : root ratio, because GSH is required specifically for the growth of the root meristem. Similarly, chloroplast γ-glutamyl cysteine synthetase overexpression could be used to increase the abundance of specific amino acids such as leucine, lysine and tyrosine that are synthesized in the chloroplasts. Here we review the aspects of glutathione biology related to synthesis, compartmentation and transport and related signalling functions that modulate plant growth and development and underpin any assessment of manipulation of GSH homeostasis from the viewpoint of nutritional genomics.     

激素对水生植物生理生态的影响及其应用

激素代谢是植物传导信号和调节生长发育的重要途径.陆地植物五大类激素在水生植物中也有分布,尽管近年来环境污染导致水生植物衰退的问题日益得到重视,但水生植物激素的研究和应用却远滞后于陆生植物.在总结了近年来激素类物质在水生植物中的研究成果,分别从激素的种类、激素的生理生态作用、激素生物合成的途径及作用的部位和机制、激素之间的相互作用.激素类物质在实验和实践上的应用等进行了全面阐述,指出了水生植物激素生理生态学研究的发展方向,从利用激素类物质诱导水生植物抗性的表达,提高抗逆性,恢复水生植被,以及研究和开发适于水生植物生产和管理的生长调节剂等方面,就水生植物激素的进一步研究和应用进行了探讨.     

植物激素在苔藓生长发育与逆境响应过程中的作用机制研究进展

植物激素是由植物自身代谢产生的一类从产生部位移动到作用部位发挥调控功能的微量小分子有机物质,在植物生长发育、响应环境胁迫过程中起到关键作用.苔藓植物作为早期登陆的非维管植物,处于陆生植物进化早期的阶段,具有许多不同于维管植物的形态和生理特征.大部分苔藓中普遍存在8种主要的植物激素及其衍生物(包括ABA、JA、ET、SA...