赤霉素作用机制研究进展

赤霉素是一种常见的植物激素,在高等植物的各个生长发育阶段都具有重要的调控作用.赤霉素与其他所有激素间都存在相互作用,其作用的方向和类型取决于组织器官、发育阶段以及环境条件,使赤霉素对植物生长发育的调控及其在不同器官中的生理功能不同.本文对近年来国内外关于赤霉素的信号传导、作用机制以及赤霉素与其他植物激素间的相互作用及其调控机理的研究进行综述,以探讨赤霉素信号应答的复杂网络体系.     

植物激素信号之间的相互作用

植物激素问的相互作用对植物的正常发育来说非常重要。不同植物激素之间存在相互协同、对抗和因果等关系,以精细调控植物的发育和对环境的反应等,植物激素信号之间的相互作用已成为植物细胞中不同信号间相互作用机制研究的模式系统。现对不同植物激素在生物合成、代谢、运输和信号转导途径等层次上的相互作用进行综述,并对这一领域的研究进行了总结和展望。     

小分子RNA在植物激素信号通路中的调控功能

植物激素是调控植物生长发育的信号分子。近年来的研究发现,小分子RNA作为基因表达调控网络的组分,参与植物激素信号途径,在植物生长发育和胁迫反应方面发挥重要作用。本文综述了miRNA和次级siRNA(Short interfering RNAs)介导的基因调控与植物激素信号通路相互作用的研究进展,主要包括生长素、赤霉素、油菜素内酯和脱落酸途径涉及的miRNA及其功能,并对不同发育过程中miRNA参与的不同激素信号通路的交叉和互作进行了讨论。     

封面说明

植物激素通过复杂的信号网络控制植物整个生长发育过程和作物重要农艺性状。近年来植物激素受体与信号转导途径、激素间相互作用方面的研究取得了重大突破,我国科学家也做出了重要的贡献,目前这一研究领域已成为国际植物科学新的研究热点。为了推动我国在这一领域的研究工作,中国科学院组织于10月18-20日在北京召开“植物激素与绿色革命”香山科学会议。《植物学通报》为配合这次学术会议,特别邀请中国科学院遗传发育所傅向东研究员和左建儒研究员以及北京大学瞿礼嘉教授组织邀约相关领域专家撰写论文,形成此“激素专辑”。此专辑基本反映了我国在这一领域的总体水平。封面显示植物株型、果实大小和果实成熟等重要性状受激素的严格控制。中国科学院植物研究所徐云远研究员设计封面图片。     

水稻叶倾角调控的分子机制研究进展

叶倾角发育是影响叶片直立程度的重要因素,而直立叶型是高产水稻株型的重要指标之一。本文综述了近年来有关水稻叶倾角基因功能鉴定和分子调控机制的研究进展。激素在水稻叶倾角发育中起主要调控作用,尤其以油菜素内酯、生长素和赤霉素三类激素的作用最大。调控过程涉及到激素的合成与信号途径,同时也存在激素间的相互作用和其他调控途径,表明水稻叶倾角的调控是一个涉及多基因共同作用和多条信号途径的复杂过程。植物激素合成基因表达异常或信号传导异常可导致叶枕近轴与远轴面细胞分裂与生长不平衡,进而改变叶倾角。     

茉莉酸调控植物生长发育和胁迫的研究进展

植物作为不可移动的生物，感知外界刺激通过改变自身信号转导对其做出反应。植物激素作为重要的信号分子，在植物应对不同生物和非生物胁迫反应中发挥作用，以调节植物生长发育并适应不断变化的环境。茉莉酸是植物体内的重要激素之一，目前它的合成途径、生理作用等已有大量研究，但对其感知环境变化并做出反应的信号转导途径以及与其他植物激素的相互作用方面的研究还有空白之处。本文主要阐述茉莉酸在调控植物生长发育、胁迫应答及其与其他植物激素的相互作用方面的研究进展。     

中国植物激素研究:过去、现在和未来

为了迎接2006年10月在北京召开的“植物激素与绿色革命”香山会议,使其更具影响力,本刊组织了一期“植物激素专辑”。本文作为此专辑的序言,对我国在该领域研究作了概述和评论,以帮助读者全面地了解我国在该领域的研究历史、现状和未来发展趋势。本文回顾了中国植物激素研究在二十世纪八十年代之前的工作发展历程中的重要成果,主要集中在生理学研究方面的成果。随着植物分子遗传学技术与原理的不断成熟以及我国经济的飞速发展,特别是研究队伍的迅速成长,我国科学家近年来在植物激素代谢调控、转运及激素信号转导等领域取得了重要进展,特别是激素受体基因分离鉴定、激素控制株型以及激素间的相互作用等方面取得的突破性进展。基于国际植物激素总体研究前沿和我国优势领域,我们展望提出了我国在植物激素研究领域的未来发展方向与趋势。     

中国植物激素研究: 过去、现在和未来

为了迎接2006年10月在北京召开的“植物激素与绿色革命”香山会议, 使其更具影响力, 本刊组织了一期“植物激素专辑”。本文作为此专辑的序言, 对我国在该领域研究作了概述和评论, 以帮助读者全面地了解我国在该领域的研究历史、现状和未来发展趋势。本文回顾了中国植物激素研究在二十世纪八十年代之前的工作发展历程中的重要成果, 主要集中在生理学研究方面的成果。随着植物分子遗传学技术与原理的不断成熟以及我国经济的飞速发展, 特别是研究队伍的迅速成长, 我国科学家近年来在植物激素代谢调控、转运及激素信号转导等领域取得了重要进展, 特别是激素受体基因分离鉴定、激素控制株型以及激素间的相互作用等方面取得的突破性进展。基于国际植物激素总体研究前沿和我国优势领域, 我们展望提出了我国在植物激素研究领域的未来发展方向与趋势。     

油菜素甾醇类与生长素的相互作用

油菜素甾醇类(brassinosteroid,BR)和生长素是两类重要的植物激素,二者在许多生理功能上存在相关性。近年来的研究表明,BR与生长素能协同调节基因表达,二者在代谢、运输和信号转导途径等不同层次上存在相互作用,并且这两种信号与其他信号转导途径,如激素信号转导途径和光信号转导途径之间也存在信号对话。现对BR与生长素之间这种复杂的相互作用进行评述。     

芸薹素与其他植物激素相互作用的研究进展

芸薹素是植物中发现的固醇类激素,对植物的生长和发育等起着非常重要的作用,而这些重要的生理功能通常又需要通过与其它植物激素的相互作用.主要对芸薹素与其他植物激素之间相互作用的研究进展进行了综述.     

Physiology and toxicology of hormone-disrupting chemicals in higher plants

Higher plants are exposed to natural environmental organic chemicals, associated with plant–environment interactions, and xenobiotic environmental organic chemicals, associated with anthropogenic activities. The effects of these chemicals result not only from interaction with metabolic targets, but also from interaction with the complex regulatory networks of hormone signaling. Purpose-designed plant hormone analogues thus show extensive signaling effects on gene regulation and are as such important for understanding plant hormone mechanisms and for manipulating plant growth and development. Some natural environmental chemicals also act on plants through interference with the perception and transduction of endogenous hormone signals. In a number of cases, bioactive xenobiotics, including herbicides that have been designed to affect specific metabolic targets, show extensive gene regulation effects, which are more in accordance with signaling effects than with consequences of metabolic effects. Some of these effects could be due to structural analogies with plant hormones or to interference with hormone metabolism, thus resulting in situations of hormone disruption similar to animal cell endocrine disruption by xenobiotics. These hormone-disrupting effects can be superimposed on parallel metabolic effects, thus indicating that toxicological characterisation of xenobiotics must take into consideration the whole range of signaling and metabolic effects. Hormone-disruptive signaling effects probably predominate when xenobiotic concentrations are low, as occurs in situations of residual low-level pollutions. These hormone-disruptive effects in plants may thus be of importance for understanding cryptic effects of low-dosage xenobiotics, as well as the interactive effects of mixtures of xenobiotic pollutants.     

A perspective for understanding the modes of juvenile hormone action as a lipid signaling system

The juvenile hormones of insects regulate an unusually large diversity of processes during postembryonic development and adult reproduction. It is a long-standing puzzle in insect developmental biology and physiology how one hormone can have such diverse effects. The search for molecular mechanisms of juvenile hormone action has been guided by classical models for hormone-receptor interaction. Yet, despite substantial effort, the search for a juvenile hormone receptor has been frustrating and has yielded limited results. We note here that a number of lipid-soluble signaling molecules in vertebrates, invertebrates and plants show curious similarities to the properties of juvenile hormones of insects. Until now, these signaling molecules have been thought of as uniquely evolved mechanisms that perform specialized regulatory functions in the taxon where they were discovered. We show that this array of lipid signaling molecules share interesting properties and suggest that they constitute a large set of signal control and transduction mechanisms that include, but range far beyond, the classical steroid hormone signaling mechanism. Juvenile hormone is the insect representative of this widespread and diverse system of lipid signaling molecules that regulate protein activity in a variety of ways. We propose a synthetic perspective for understanding juvenile hormone action in light of other lipid signaling systems and suggest that lipid activation of proteins has evolved to modulate existing signal activation and transduction mechanisms in animals and plants. Since small lipids can be inserted into many different pathways, lipid-activated proteins have evolved to play a great diversity of roles in physiology and development.     

Growth hormone signaling is necessary for lifespan extension by dietary methionine

Growth hormone significantly impacts lifespan in mammals. Mouse longevity is extended when growth hormone (GH) signaling is interrupted but markedly shortened with high‐plasma hormone levels. Methionine metabolism is enhanced in growth hormone deficiency, for example, in the Ames dwarf, but suppressed in GH transgenic mice. Methionine intake affects also lifespan, and thus, GH mutant mice and respective wild‐type littermates were fed 0.16%, 0.43%, or 1.3% methionine to evaluate the interaction between hormone status and methionine. All wild‐type and GH transgenic mice lived longer when fed 0.16% methionine but not when fed higher levels. In contrast, animals without growth hormone signaling due to hormone deficiency or resistance did not respond to altered levels of methionine in terms of lifespan, body weight, or food consumption. Taken together, our results suggest that the presence of growth hormone is necessary to sense dietary methionine changes, thus strongly linking growth and lifespan to amino acid availability.     

Mechanisms of action of the congenital diaphragmatic hernia-inducing teratogen nitrofen

Congenital diaphragmatic hernia (CDH) is a developmental anomaly that results in significant mortality and morbidity. The underlying etiology is poorly understood. Insights will arise from an understanding of the mechanisms by which the teratogen nitrofen induces CDH in rodent models. In this study, we use in vitro cell assays in conjunction with whole animal rodent studies to test hypotheses regarding nitrofen's mechanism of action. The first component examined the interaction of nitrofen with various aspects of the retinoid signaling pathway including uptake proteins, binding proteins, receptors, conversion, and degradation enzymes. The second component examined the interactions of nitrofen and vitamins A, C, and E to test the hypothesis that nitrofen was functioning as an antioxidant to interfere with retinoid signaling. Third, we performed a series of experiments examining the interaction of nitrofen and thyroid signaling. Collectively, the data suggest that the primary aspect of retinoid signaling affected by nitrofen is via inhibition of the rate-limiting enzymes controlling retinoic acid synthesis. Retinoid signaling perturbations do not appear to involve oxidative effects of nitrofen. Any substantial roles of nitrofen-induced perturbations of thyroid hormone signaling or receptor function are not supported.     

A regulator of G Protein signaling, RGS3, inhibits gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH) secretion

Background  

Luteinizing hormone secreted by the anterior pituitary gland regulates gonadal function. Luteinizing hormone secretion is regulated both by alterations in gonadotrope responsiveness to hypothalamic gonadotropin releasing hormone and by alterations in gonadotropin releasing hormone secretion. The mechanisms that determine gonadotrope responsiveness are unknown but may involve regulators of G protein signaling (RGSs). These proteins act by antagonizing or abbreviating interaction of Gα proteins with effectors such as phospholipase Cβ. Previously, we reported that gonadotropin releasing hormone-stimulated second messenger inositol trisphosphate production was inhibited when RGS3 and gonadotropin releasing hormone receptor cDNAs were co-transfected into the COS cell line. Here, we present evidence for RGS3 inhibition of gonadotropin releasing hormone-induced luteinizing hormone secretion from cultured rat pituitary cells.     

Roles of F-box proteins in plant hormone responses

The F-box protein is an important component of the E3 ubiquitin ligase Skpl-Cullin-F-box protein complex. It binds specific substrates for ubiquitin-mediated proteolysis. The F-box proteins contain a signature F-box motif at their amino-terminus and some protein-protein interaction motifs at their carboxyterminus, such as Trp-Asp repeats or leucine rich repeats. Many F-box proteins have been identified to be involved in plant hormone response as receptors or important medial components. These breakthrough findings shed light on our current understanding of the structure and function of the various F-box proteins, their related plant hormone signaling pathways, and their roles in regulating plant development.     

Hormone response element binding proteins: novel regulators of vitamin D and estrogen signaling

Insights from vitamin D-resistant New World primates and their human homologues as models of natural and pathological insensitivity to sterol/steroid action have uncovered a family of novel intracellular vitamin D and estrogen regulatory proteins involved in hormone action. The proteins, known as “vitamin D or estrogen response element-binding proteins”, behave as potent cis-acting, transdominant regulators to inhibit steroid receptor binding to DNA response elements and is responsible for vitamin D and estrogen resistances. This set of interactors belongs to the heterogeneous nuclear ribonucleoprotein (hnRNP) family of previously known pre-mRNA-interacting proteins. This review provides new insights into the mechanism by which these novel regulators of signaling and metabolism can act to regulate responses to vitamin D and estrogen. In addition the review also describes other molecules that are known to influence nuclear receptor signaling through interaction with hormone response elements.