影响植物分枝的一些基因及其分子机制

了解植物分枝机理不仅具有理论意义,对于农业、林业、果树、蔬菜和花卉等生产实践更具有重要意义.由于分子生物学的发展,人们有机会获得转基因植物和突变体,利用这些材料从不同角度对植物分枝机理进行深入研究.影响植物分枝的分子机制是多种多样的,对激素感知、激素代谢、激素运输等方面的影响都可以改变植物的分枝状况.目前,分枝的分子机制研究已取得较大进展.     

植物激素调控腋生分生组织发育的研究进展

植物分枝的生长是植物发育的一个标志性生长特征,不仅影响着植物株型的多样化,而且也影响着植物的生产力。植物分枝是由腋生分生组织（Axillary Meristems,AMs）实现的,腋生分生组织分布在每个叶基的腋部,并发育成分枝。因此,腋生分生组织发育分化规律的研究,不仅是植物生长发育的基础问题,而且对植物的实践生产也具有重要的指导意义。近年来,随着植物激素合成、信号途径等突变体被分离、鉴定以及相应基因被克隆,人们在植物激素调控腋生分生组织发育方面有了深入的了解。本文对生长素、细胞分裂素、赤霉素和独角金内酯等植物激素在植物腋生分生组织形成与发育过程中的调控机制进行阐述,认为随着新的检测工具和分析技术的发展,未来应加强环境信号介导下植物激素互作对腋生分生组织发育的研究。     

菌根共生体中植物信号物质的产生及其作用机制

菌根是丛枝菌根真菌与宿主植物形成的互利共生体,在共生的不同阶段,植物产生一系列的信号物质如独脚金内酯、溶血磷脂酰胆碱、茉莉酸和水杨酸等.这些信号物质在植物与丛枝菌根真菌间相互识别、菌根形成、营养物质交换,以及植物防御反应诱导等方面发挥重要作用.文中探讨植物信号物质在丛枝菌根共生系统形成前后和病原体侵害的3个阶段可能的生理效应和作用机制,旨在为研究丛枝菌根真菌与植物信号物质的相互作用及其在农业生产和环境保护方面的应用提供依据.     

植物免疫受体病原体识别机制的结构生物学研究进展

在与病原体的长期抗争中,植物进化出双重天然免疫系统,即病原体相关分子模式触发的免疫(PTI)和病原体效应因子触发的免疫(ETI),其中模式识别受体(PRR)和核苷酸结合富亮氨酸重复受体(NLR)分别在这两道防线中以多种方式发挥识别作用.以植物免疫受体和病原体配体结构生物学研究为基础,综述了5种由PRR和NLR介导的病原体识别机制的类型:PRR介导的直接(类型一)或间接(类型二)的病原体识别机制;NLR介导的直接(类型三)或间接(类型四)的病原体识别机制以及依赖NLR的集成结构域(ID)(类型五)的病原体识别机制.植物免疫受体的蛋白结构解析结合其识别机制的功能研究,将会为作物抗病工程开辟全新的道路.     

植物生长调节剂的发展前景

1 植物生长调节剂的研究与发展 植物生长调节剂的研究工作,是从研究植物激素开始的。本世纪30年代,科学家在植物体内首先发现生长素,当它的化学结构式尤其是功效被揭示后,激素的研究与开发工作便竞相开展起来。从50年代始到60年代后期,又先后发现了赤霉素、细胞分裂素、脱落酸和乙烯4种植物激素,并很快弄清楚了它们的构效。特别是各种激素     

植物激素-赤霉素(GA)细胞信号转导机制

植物激素赤霉素(GA)参与植物种子萌发、茎伸长、开花、结果等多个生长发育过程.研究GA细胞信号转导的分子机制对进一步阐明其生物学功能具有重要的意义.GA合成突变体和细胞信号转导突变体的研究表明,GAI及其同功蛋白具有受体功能,GA被受体识别后进一步与DELLA蛋白作用,从而解除DELLA蛋白对植物生长的抑制作用.文章主要综述这些分子具体的作用模式.     

植物LRR类受体蛋白激酶的研究进展

简要介绍了LRR-类受体蛋白激酶(LRR-RLKs)的胞外LRR基序和胞内丝/苏氨酸激酶区的结构特点;LRR-RLKs在调节植物生长发育和防卫反应方面的生理功能及其与配体互作的2种可能机制:LRR-RLKs受体磷酸化和LRR-RLKs受体去磷酸化.讨论发现,LRR-RLKs的结构特点和多样化的基因表达方式,是其具有多种生理功能的基础;植物信号传导途径的复杂性和不同蛋白的功能互补,则可能是导致LRR-RLKs的功能和作用方式至今尚未解释清楚的重要原因.利用日趋先进的生物技术,加强对配体和下游信号分子的搜寻、鉴定和识别,将是今后LRR-RLKs研究的有效途径.     

紫外光B波段光信号调控植物生长发育的研究进展

光作为重要的环境因子从多方面调控着植物生长发育.植物能感知不同波段的光并做出适当的反应来适应环境中不断变化的光信号.研究发现,植物进化出不同的光受体来接收远红光、红光、蓝光和紫外光信号.在光受体下游,光信号经复杂的信号转导网络以及全基因组表达变化来指导植物的生长发育,使得植物能够适应周围的光照环境.紫外光B波段(UV-B)光受体UVR8(UV Resistance Locus 8)接收到UV-B光后将信号向下游传递,通过调控蛋白COP1(Constitutively Photomorphogenic 1)、RUP1/2(Repressor of UV-B Photomorphogenesis 1/2)和转录因子HY5(Elongated Hypocotyl 5)等核心信号因子将光信号传递到UV-B光应答基因,启动植物对UV-B光信号的响应.自2011年UV-B光受体被鉴定以来,近10年的研究逐步揭示了一系列UV-B光信号转导的分子机制,本文围绕相关研究进展进行综述.     

LysM蛋白在植物免疫中的作用

溶解素基序（LysM）是在多种蛋白质中普遍存在的结构域.植物LysM蛋白能够感知几丁质及其寡糖等分子配体，从而启动植物对病原菌的免疫反应.在水稻、拟南芥等植物免疫应答过程中，LysM蛋白作为一种重要的模式识别受体，通过不同形式的寡聚化，激活多种类受体胞质激酶及其下游的MAPK（mitogen activated protein kinase）级联反应传递信号.同时，蛋白质可逆磷酸化和蛋白质降解途径可以负调节LysM蛋白介导的防御信号转导.文章综述了植物免疫过程中LysM蛋白介导的信号转导分子机制.     

植物模式识别受体FLS2的研究进展

植物通过模式识别受体识别病原微生物保守的分子,开启第一层次免疫屏障,以此实现对各种微生物的非寄主抗性和产生基础防御。第一个被鉴定的植物模式识别受体是识别细菌鞭毛蛋白的拟南芥FLS2,围绕FLS2的大量研究为其他模式识别受体的研究提供了范例,促进了植物免疫理论的建立和发展。通过介绍FLS2的发现过程、命名过程的插曲、结构与功能、激活步骤与相关元件、调控的分子机制、FLS2与病原微生物效应因子的相互作用以及FLS2在被子植物中的系统发生关系,对FLS2研究中显现的蛋白污染和C末端标签问题进行了分析,并介绍了依靠遗传转化植物模式识别受体基因,培育广谱耐久抗病植物的前景。     

Strigolactone inhibition of shoot branching

A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactones are compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds and stimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of pea are strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants. Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibition signal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis. In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots and act at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching in plants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizal symbiosis and parasitic weed interaction.     

Progress in quantitative analysis of plant hormones

Plant hormones are small molecular natural products that regulate all plant developmental processes at low concentrations. Quantitative analysis of plant hormones is increasingly important for in-depth study of their biosynthesis, transport, metabolism and molecular regulatory mechanisms. Although plant hormone analysis remains a bottleneck in plant scientific research owing to the trace concentrations and complex components in plant crude extracts, much progress has been achieved in the development of extraction, purification and detection techniques in recent years. Solid phase extraction and chromatography/mass spectrometry have been applied widely for purification and quantitative analysis of plant hormones owing to their high selectivity and sensitivity. Purification methods such as liquid partition and immunoaffinity chromatography, and detection methods including immunoassay and electrochemical analysis, are employed. The advantages and disadvantages of these methods are discussed. In situ, real-time and multi-plant hormone profiling will comprise mainstream techniques for quantitative analyses in future studies on the regulatory mechanisms and crosstalk of plant hormones.     

Inhibition of shoot branching by new terpenoid plant hormones

Shoot branching is a major determinant of plant architecture and is highly regulated by endogenous and environmental cues. Two classes of hormones, auxin and cytokinin, have long been known to have an important involvement in controlling shoot branching. Previous studies using a series of mutants with enhanced shoot branching suggested the existence of a third class of hormone(s) that is derived from carotenoids, but its chemical identity has been unknown. Here we show that levels of strigolactones, a group of terpenoid lactones, are significantly reduced in some of the branching mutants. Furthermore, application of strigolactones inhibits shoot branching in these mutants. Strigolactones were previously found in root exudates acting as communication chemicals with parasitic weeds and symbiotic arbuscular mycorrhizal fungi. Thus, we propose that strigolactones act as a new hormone class-or their biosynthetic precursors-in regulating above-ground plant architecture, and also have a function in underground communication with other neighbouring organisms.     

Progress in quantitative analysis of plant hormones

Plant hormones are small molecular natural products that regulate all plant developmental processes at low concentrations. Quantitative analysis of plant hormones is increasingly important for in-depth study of their biosynthesis,transport,metabolism and molecular regulatory mechanisms. Although plant hormone analysis remains a bottleneck in plant scientific research owing to the trace concentrations and complex components in plant crude extracts,much progress has been achieved in the development of extraction,purification and detection techniques in recent years. Solid phase extraction and chromatography/mass spectrometry have been applied widely for purification and quantitative analysis of plant hormones owing to their high selectivity and sensitivity. Purification methods such as liquid partition and immunoaffinity chromatography,and detection methods including immunoassay and electrochemical analysis,are employed. The advantages and disadvantages of these methods are discussed. In situ,real-time and multi-plant hormone profiling will comprise mainstream techniques for quantitative analyses in future studies on the regulatory mechanisms and crosstalk of plant hormones.     

Plant sesquiterpenes induce hyphal branching in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi form mutualistic, symbiotic associations with the roots of more than 80% of land plants. The fungi are incapable of completing their life cycle in the absence of a host root. Their spores can germinate and grow in the absence of a host, but their hyphal growth is very limited. Little is known about the molecular mechanisms that govern signalling and recognition between AM fungi and their host plants. In one of the first stages of host recognition, the hyphae of AM fungi show extensive branching in the vicinity of host roots before formation of the appressorium, the structure used to penetrate the plant root. Host roots are known to release signalling molecules that trigger hyphal branching, but these branching factors have not been isolated. Here we have isolated a branching factor from the root exudates of Lotus japonicus and used spectroscopic analysis and chemical synthesis to identify it as a strigolactone, 5-deoxy-strigol. Strigolactones are a group of sesquiterpene lactones, previously isolated as seed-germination stimulants for the parasitic weeds Striga and Orobanche. The natural strigolactones 5-deoxy-strigol, sorgolactone and strigol, and a synthetic analogue, GR24, induced extensive hyphal branching in germinating spores of the AM fungus Gigaspora margarita at very low concentrations.     

A petunia ABC protein controls strigolactone-dependent symbiotic signalling and branching

Strigolactones were originally identified as stimulators of the germination of root-parasitic weeds that pose a serious threat to resource-limited agriculture. They are mostly exuded from roots and function as signalling compounds in the initiation of arbuscular mycorrhizae, which are plant-fungus symbionts with a global effect on carbon and phosphate cycling. Recently, strigolactones were established to be phytohormones that regulate plant shoot architecture by inhibiting the outgrowth of axillary buds. Despite their importance, it is not known how strigolactones are transported. ATP-binding cassette (ABC) transporters, however, are known to have functions in phytohormone translocation. Here we show that the Petunia hybrida ABC transporter PDR1 has a key role in regulating the development of arbuscular mycorrhizae and axillary branches, by functioning as a cellular strigolactone exporter. P. hybrida pdr1 mutants are defective in strigolactone exudation from their roots, resulting in reduced symbiotic interactions. Above ground, pdr1 mutants have an enhanced branching phenotype, which is indicative of impaired strigolactone allocation. Overexpression of Petunia axillaris PDR1 in Arabidopsis thaliana results in increased tolerance to high concentrations of a synthetic strigolactone, consistent with increased export of strigolactones from the roots. PDR1 is the first known component in strigolactone transport, providing new opportunities for investigating and manipulating strigolactone-dependent processes.     

外来入侵植物喜旱莲子草的研究进展

喜旱莲子草已经成为我国的恶性入侵杂草.本文从喜旱莲子草的自身繁殖特性、生理生态适应性、群落内的种间关系、遗传多样性及其防治研究等方面综述近年来的研究现状,同时针对目前研究中存在的问题探讨今后喜旱莲子草研究的发展方向.大量的研究表明,喜旱莲子草的繁殖特性可能是影响它入侵的主要因子.但在入侵过程中它对各种环境的适应性是极为多样的,有可能是多方面的综合因素决定了其入侵的成功.