矿质营养对生长素代谢影响的研究现状与展望

植物从环境中吸收的矿质元素直接参与植物生理代谢,植物内源激素对植物生理代谢具有重要的调节作用,矿质营养与植物内源激素的相互关系一直是植物营养研究的重要内容。生长素是植物五大内源激素之一,对细胞的分裂和伸长具有重要的调节作用。本文从矿质营养对ＩＡＡ的量及分布,矿质营养对ＩＡＡ合成,矿质营养对ＩＡＡ运输,矿质营养对ＩＡＡ的转化等方面对矿质营养与生长素的关系的研究进展进行了概述,并对矿质营养与生长素的关系的进一步研究进行了展望。     

重金属对植物吲哚乙酸合成与分解影响研究进展

生长素在调节植物生长和抗重金属胁迫中具有重要作用。重金属胁迫下植物为维持自身生长,必须维持生长素的内稳态和自身代谢平衡。生长素的内稳态受到生物合成、生长素结合以及水解、代谢失活等生理活动的严格控制。一些涉及生长素合成与分解的相关酶系和基因已被识别或克隆,然而重金属胁迫下与生长素合成与分解有关基因的上调或下调以及相关酶系的激活或失活却研究尚少。揭示植物遭受重金属胁迫后生长素合成与分解变化的机理,可为植物修复实践中合理使用植物生长调节剂提供理论依据。本文以生长素的主要代表物吲哚乙酸(IAA)为例,讨论重金属胁迫下,植物体内IAA合成、分解机制及其赋存形态等方面的研究进展,并从重金属胁迫下植物IAA合成途径的相对重要性、IAA形态变化和作用以及激素间的交互作用等方面探讨了该领域的研究方向。     

吲哚乙酸跨界信号调节植物与细菌互作

吲哚-3-乙酸(indole-3-acetic acid,IAA)作为植物体内普遍存在的内源生长素参与调节植物生命活动的诸多方面。研究发现,自然界中不仅植物可以合成IAA,许多微生物(包括植物病原菌或益生菌)同样具有分泌IAA的能力,可以诱发植物病害,或促进植物生长。有趣的是IAA不仅作为细菌的次生代谢物干扰寄主植物的激素稳态,也作为信号分子影响细菌基因表达和生理活动,通过整合进入细菌复杂代谢网络,调节植物与细菌的相互作用。通过讨论植物相关细菌IAA的生物合成途径及其调控,以及参与调节细菌基因表达、影响细菌生理和行为及其与寄主植物的互作等,概述该领域的研究动态与进展,揭示IAA不仅调节植物生长发育和防御,也作为跨界信号在调控植物与微生物互作中发挥重要作用,旨在为深入研究和更好地了解IAA跨界信号机制,通过遗传操纵细菌IAA信号通路以改善植物生长发育及其胁迫耐力提供新思路。     

生长素的信号传导与泛素化作用

生长素是植物体内一类非常重要的内源激素,它控制着植物的细胞伸长,顶端优势,侧根发生及维管束的发育等重要的生理过程。研究表明,生长素领带传导与泛素介导的某些蛋白质的降解过程密切相关。本文对生长素信号传导与泛素化作用的最新研究进展进行了综述。     

不同载畜率下短花针茅分蘖数量对内源激素浓度的响应

放牧是荒漠草原最主要的利用方式之一,载畜率的变化严重影响着植物的生长发育;而内源植物激素是调节植物生长发育的开关,且植物在不同的生长发育阶段具有不同的生理要求和环境适应能力。通过测定放牧条件下短花针茅(Stipa breviflora)分蘖叶内源激素的变化,研究短花针茅分蘖生长对放牧的响应,并分析了分蘖数量受内源激素影响的机制。结果表明,(1)内源激素与载畜率之间存在显著二次相关关系,说明放牧能够显著增加内源激素的浓度(P0.05),但这种相关只存在于中、小株丛的短花针茅中。(2)其次,放牧能够在一定程度上影响短花针茅植株个体分蘖的数量(P0.05),重度放牧是增加短花针茅植株个体分蘖数量最显著的载畜率。(3)过高浓度的生长素(IAA)会抑制短花针茅的分蘖数量(P0.01)。而细胞分裂素(CTK)与短花针茅的分蘖数量之间尚未发现相关关系。     

质谱技术在植物内源激素检测中的应用(综述)

植物内源激素对植物的各种生理活动具有显著的调节作用,但含量极少,对其进行超微量定量检测具有重要意义。在各种检测方法中,质谱法因具有高效、快速、灵敏的优点而得以广泛应用。本文综述近年来质谱技术在植物内源激素检测中的应用,包括样品前处理方法、有机质谱联用技术(气相色谱-质谱、液相色谱-质谱)和生物质谱等,并探讨其未来研究方向。     

植物离体培养中器官发生调控机制的研究进展

本文就离体培养的植物组织对生长调节物质的吸收和代谢,外源生长调节物质对内源激素水平的影响,内源激素对细胞脱分化和再分化的调控,生长素和细胞分裂素基因与器官发生的关系,与器官发生有关的基因和特异蛋白等问题的研究进展进行了评述,并对下一步研究提出了自己的看法。     

生长素在微生物调控根发育过程中的作用

很多微生物通过分泌生长素和生长素前体与植物建立了有益的关系并改变植物根系的形态结构,此外,微生物分泌的其他代谢产物也能改变植物生长素信号通路。因此,生长素和生长素信号通路在微生物调控植物根系发育的过程中起着至关重要的作用。该文从生长素合成、生长素信号和生长素极性运输3个方面总结了生长素在微生物调控植物根系发育过程中的作用,主要包括微生物增加了植物内源生长素的含量、增强了生长素的信号和调控PIN蛋白的表达水平,进而如何调控植物生理和分子水平来适应微生物对其根系的改变,为进一步开展该方面的研究奠定了基础。     

植物离体培养中器官发生调控机制的研究进展

本文就离体培养的植物组织对生长调节物质的吸收和代谢，外源生长调节物质对内源激素水平的影响，内源激素对细胞脱分化和再分化的调控，生长素和细胞分裂素基因与器官发生的关系，与器官发生有关的基因和特异蛋白等问题的研究进展进行了评述，并对下一步研究提出了自己的看法。     

黄芪幼苗根系生长发育与GR24和IAA的关系北大核心CSCD

为探究独脚金内酯和生长素对黄芪根系生长发育的影响,该研究以膜荚黄芪和蒙古黄芪幼苗为材料,在种子萌发袋中添加不同浓度GR24和IAA(2μmol·L^(-1) GR24、5μmol·L^(-1) IAA和2μmol·L^(-1) GR24+5μmol·L^(-1) IAA),7 d后检测黄芪幼苗主根长和侧根数,并测定内源激素含量、生长素和独脚金内酯相关基因表达量的变化。结果表明:(1)GR24处理显著促进黄芪主根生长。(2)IAA处理下主根生长受到抑制,侧根数明显增加。(3)GR24+IAA处理下主根的生长同样受到抑制,膜荚黄芪侧根数较IAA处理下减少,说明GR24有抑制IAA对侧根发育的诱导作用,但不能缓解IAA对黄芪主根生长的抑制。(4)3种处理下黄芪幼苗根系内源激素含量、生长素和独脚金内酯相关基因表达量发生了显著变化,说明GR24和IAA对黄芪幼苗主根长和侧根数的影响可能与生长素和独脚金内酯相关基因表达及内源激素水平的变化有关。该研究结果初步阐明了黄芪幼苗根系生长发育与GR24和IAA之间的关系,为黄芪规范化育苗和幼苗质量控制提供理论依据,对进一步探索独脚金内酯和生长素调控黄芪根系生长发育的分子机制具有一定的意义。     

Parasitic Nematodes Modulate PIN-Mediated Auxin Transport to Facilitate Infection

Plant-parasitic nematodes are destructive plant pathogens that cause significant yield losses. They induce highly specialized feeding sites (NFS) in infected plant roots from which they withdraw nutrients. In order to establish these NFS, it is thought that the nematodes manipulate the molecular and physiological pathways of their hosts. Evidence is accumulating that the plant signalling molecule auxin is involved in the initiation and development of the feeding sites of sedentary plant-parasitic nematodes. Intercellular transport of auxin is essential for various aspects of plant growth and development. Here, we analysed the spatial and temporal expression of PIN auxin transporters during the early events of NFS establishment using promoter-GUS/GFP fusion lines. Additionally, single and double pin mutants were used in infection studies to analyse the role of the different PIN proteins during cyst nematode infection. Based on our results, we postulate a model in which PIN1-mediated auxin transport is needed to deliver auxin to the initial syncytial cell, whereas PIN3 and PIN4 distribute the accumulated auxin laterally and are involved in the radial expansion of the NFS. Our data demonstrate that cyst nematodes are able to hijack the auxin distribution network in order to facilitate the infection process.     

Manipulation of Auxin Transport in Plant Roots during Rhizobium Symbiosis and Nematode Parasitism

The plant rhizosphere harbors many different microorganisms, ranging from plant growth–promoting bacteria to devastating plant parasites. Some of these microbes are able to induce de novo organ formation in infected roots. Certain soil bacteria, collectively called rhizobia, form a symbiotic interaction with legumes, leading to the formation of nitrogen-fixing root nodules. Sedentary endoparasitic nematodes, on the other hand, induce highly specialized feeding sites in infected plant roots from which they withdraw nutrients. In order to establish these new root structures, it is thought that these organisms use and manipulate the endogenous molecular and physiological pathways of their hosts. Over the years, evidence has accumulated reliably demonstrating the involvement of the plant hormone auxin. Moreover, the auxin responses during microbe-induced de novo organ formation seem to be dynamic, suggesting that plant-associated microbes can actively modify their host''s auxin transport. In this review, we focus on recent findings in auxin transport mechanisms during plant development and on how plant symbionts and parasites have evolved to manipulate these mechanisms for their own purposes.     

A role for the root cap in root branching revealed by the non-auxin probe naxillin

The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture.     

Shoot Apex Demand Determines Assimilate and Nutrients Partitioning and Nutrient-uptake Rate in Tobacco Plants

Our previous experiment revealed that apex-removed plants have larger root systems but a lower K＋-uptake rates than intact tobacco plants. Since the apex is not only a center of growth and metabolism, but also an important place of auxin synthesis and export, the aims of this study were to distinguish whether the apex demand or auxin synthesized in the apex regulates assimilate and nutrients partitioning within plant, and to explain the reason for the lower K＋-uptake rate of the apex-removed plant. In comparison with the control plant, covering the shoot apex with a black transparent plastic bag reduced net increases in dry matter and nutrients; however, the distribution of the dry matter and nutrients between shoot and roots and nutrient-uptake rates were not changed. Removal of the shoot apex shifted the dry mass and nutrients distributions to roots, and reduced the rate of nutrient uptake. Application of 1-naphthylacetic acid （NAA） could partly replace the role of the removed apex, stimulated assimilate and nutrient deposition into the treated tissue, and enhanced the reduced plasma membrane ATPase activity of roots to the control level. However, treatment of the apex-removed plants with NAA could not rescue the reduced nutrient uptake rate and the shifted assimilates and nutrients partitioning caused by excision of the apex. Higher nutrient uptake rate of the intact plants could not be explained by root growth parameters, such as total root surface area and number of root tips. The results from the present study indicate that strong apex demand determined assimilates and nutrients partitioning and nutrient-uptake rate in tobacco （Nicotiana tabacum） plants.     

Apical dominance

Apical dominance is the control exerted by the apical portions of the shoot over the outgrowth of the lateral buds. The classical explanations for correlative inhibition have focused on hormone/nutrient hypotheses. The remarkable progress that has been made in the technology of endogenous hormone quantification in plant tissue has not been accompanied by comparable progress in the elucidation of mechanisms of hormone action in apical dominance. Evidence from hormonal studies suggests that apically produced auxin indirectly suppresses axillary bud outgrowth that is promoted by cytokinin originating from roots/shoots. Significant involvement with other hormones, although less likely, has not been ruled out. Possible changes in tissue sensitivity to hormones should not be overlooked. Auxin-induced oligosaccharide signals originating from the cell walls of shoot tips or polyamines may function as secondary inhibitors to bud growth. Alternatively, apically produced auxin may suppress lateral bud growth by inhibiting auxin export from these buds. Support for a critical role for nutrients in apical dominance keeps resurfacing, especially for auxin-directed nutrient transport and for water as a possible inducing signal for bud outgrowth. Histological and biochemical analyses of lateral buds recently released from apical dominance are urgently needed. The feasibility of manipulating endogenous auxin/cytokinin content in plant tissue by gene insertion and modulation opens the door to exciting approaches as does the use of hormone insensitive/resistant mutants. There is also need to recognize the existence of variability of apical dominance mechanisms among different plant types. The aesthetic and economic implications of understanding apical dominance for the modification of plant structure and form are extremely significant.     

Auxin signals--turning genes on and turning cells around

The extremely wide spectrum of the plant processes that are influenced by auxin raises the question of how signals conveyed by a single molecule can trigger such a variety of responses. Although many aspects of auxin function remain elusive, others have become genetically tractable. The identification of crucial genes in auxin signal transduction and auxin transport in the past few years has led to molecularly testable concepts of how auxin signals regulate gene activities in individual cells, and how the polar transport of auxin could impact on patterning processes throughout the plant.     

Organic acids, sugars, and L-tryptophane in exudates of vegetables growing on stonewool and their effects on activities of rhizosphere bacteria

The influence of stonewool substrate on the exudation of the major soluble carbon nutrients and of the auxin precursor tryptophane for Pseudomonas biocontrol agents was studied. To this end, the composition of the organic acids and sugars, as well that of tryptophane, of axenically collected exudates of seed, seedlings, and roots of tomato, cucumber, and sweet pepper was determined. The major results were as follows. i) The total amount of organic acid is much higher than that of total sugar. ii) Exudation of both organic acids and sugars increases during plant growth. iii) Citric, succinic, and malic acids represent the major organic acids, whereas fructose and glucose are the major sugars. iv) Compared with glass beads as a neutral substrate, stonewool substantially stimulates exudation of organic acids and sugars. v) It appeared that enhanced root-tip-colonizing bacteria isolated previously from the rhizosphere of tomato and cucumber grow much better in minimal medium with citrate as the sole carbon source than other, randomly selected rhizobacteria do. This indicates that the procedure which selects for excellent root-tip colonizers enriches for strains which utilize the major exudate carbon source citrate. vi) The content of L-tryptophane, the direct precursor of auxin, is approximately 60-fold higher in seedling exudates of tomato and sweet pepper than in cucumber seedling exudates, indicating a higher possibility of plant growth stimulation after inoculation with auxin-producing rhizobacteria for tomato and sweet pepper crops than for cucumber. However, the biocontrol strain Pseudomonas fluorescens WCS365, which is able to convert tryptophane into auxin, did not stimulate growth of these three crops. In contrast, this strain did stimulate growth of roots of radish, a plant which exudes nine times more tryptophane than tomato does.