氨基酸转运蛋白介导植物免疫研究进展

植物生长发育需要大量的氮素养分,氨基酸作为大多数植物体内主要的氮素运输形式,影响植物整个生命活动。氨基酸转运蛋白负责氨基酸在组织和细胞间的跨膜运输,其通过调节植物体内氨基酸稳态,影响着植物的生长发育和抗逆能力。近年来,氨基酸和氨基酸转运蛋白在植物免疫和抗病中的功能及其调控机制取得了一些突破性的研究进展。我们详细阐述了氨基酸运输、代谢在植物防御中的作用,总结了参与植物免疫的氨基酸透性酶家族(AAPs)、赖氨酸组氨酸转运蛋白家族(LHTs)、阳离子氨基酸转运蛋白家族(CATs)以及多种酸进出转运蛋白家族(UMAMITs)基因在病原菌侵染植物过程中的调节机制。转运蛋白LHT1不仅介导植物根系氨基酸的吸收和地上部氨基酸的转运,还参与了植物生长和免疫调节。本文以LHT1为例,对比了拟南芥和水稻lht1突变体植物在感染病原菌后自身的免疫过程,突出其在参与植物感染活体营养型和死体营养型病原菌过程中功能的差异性,构建了氨基酸转运蛋白调控植物免疫过程的基本分子模型。未来研究需要重点解析：1)哪些氨基酸是植物防御机制的关键营养或信号物质;2)病原菌侵染植物后,植物体内氨基酸信号的传导过程;3)植物氨基酸转...     

植物体对硝态氮的吸收转运机制研究进展

硝态氮是高等植物重要的氮素营养,直接影响植物的生长。植物根系吸收硝态氮并向地上部转运的机制一直是研究者十分关注的问题。近几年的深入研究使得新的现象与结论被揭示,推动了我们对植物体吸收转运硝态氮生理与分子机制的认识。本文综述了近年来国内外关于植物硝态氮吸收转运的生理及分子机制的相关研究结果。通过整理归类植物硝酸盐吸收相关的生理学数据,介绍了影响植物吸收硝态氮的各种因素。基于膜转运体在植物硝态氮吸收转运过程中发挥的重要作用,本文还重点介绍参与该过程的四大基因家族的成员及功能,即硝酸盐转运体1(NRT1)、硝酸盐转运体2(NRT2)、氯离子通道(CLC)和s型阴离子通道(SLAC),以期为后续研究者提供一个较为全面的理论依据。     

植物氮素利用途径中硝酸盐转运基因的研究进展

氮素是植物生长发育必不可少的大量元素之一,土壤中的硝酸盐是植物获取氮素的主要来源。植物对硝酸盐的吸收与利用是通过一个精密的信号调控网络来实现的,其中硝酸盐转运蛋白在植物体内硝酸盐的运输和分配过程中发挥着重要的作用。通过对氮素利用途径中不同硝酸盐转运基因在硝酸盐的吸收、转运、同化和再利用进行功能鉴定,可以更好地解析硝酸盐在植物体内的吸收机制,从而找到提高植物氮素利用效率的关键环节。因此,综述了植物硝酸盐转运蛋白对土壤中硝酸盐的响应和信号的传递;硝酸盐转运蛋白在植株体内参与硝酸盐的转运、储存和再利用的功能以及硝酸盐在植物育种中的应用,并从对硝酸盐转运基因的单碱基编辑、关键结构域的改造和基因功能鉴定等方面进行展望。综述了有利于揭示硝酸盐转运基因的功能,拓宽植物吸收转运硝酸盐的分子机制认识,为提高植物氮素利用效率、培育氮高效利用农作物品种提供理论支撑。     

植物对氨基酸的吸收利用及氨基酸在农业中的应用

植物对氨基酸的吸收、转运、代谢以及氨基酸在肥料和农药上的应用国内外已有报道。已有研究证明,植物可直接吸收土壤中的氨基酸分子,其吸收后的转运、分配、代谢因氨基酸种类而异,产生的生理效应也不相同;氨基酸农药易被日光分解或被自然界微生物降解,在土壤中、植物体内不留残毒,其降解产物还可作为农作物的营养物质,提高农作物的品质和产量,施用这类农药,人畜安全,没有公害;氨基酸肥具有促进植株生长发育、增强抗逆性、改善土壤状况和提高作物产量的作用。     

植物氮素吸收利用相关NPF基因家族研究进展

氮(N)是植物生长发育需要量最大的矿质营养元素,也是作物产量的限制因子。硝态氮(NO₃^--N)是植物吸收利用氮素的主要形态之一。目前,植物中已报道4个基因家族(NPF、NRT2、CLC和SLAC1/SLAH)参与硝态氮的吸收和利用,其中NPF基因家族成员数量众多且功能多样化,近年来获得较多关注和深入研究。模式植物拟南芥和主要粮食作物水稻、玉米和小麦中,分别含有53、93、79和331个NPF基因。拟南芥NPF家族中已有超过一半成员(31/53)的生物学功能被解析,粮食作物水稻中NPF基因功能亦有较多报道。研究表明,NPF基因广泛参与了植物对氮素的吸收及其调控、转运、分配/再分配等过程,一些成员对于改良和提高作物氮素利用率(nitrogen use efficiency, NUE)具有重要作用。因此,从氮素进入植物体及其在植物体内流动的层面出发,发掘具有重要功能的候选NPF基因,对于解析植物利用氮素的分子机制及其遗传改良具有重要意义。本文综述了模式植物拟南芥以及粮食作物中已报道的NPF基因在氮素吸收和利用中的生物学功能。目前粮食作物玉米中仅有4...     

植物吸收转运硝态氮及其信号调控研究进展

硝态氮是植物吸收利用的主要氮源,其吸收利用是一个高度协调复杂的调控过程。植物为了在各种变化的环境中生存,进化出了适宜不同环境的硝态氮吸收利用机制。植物根系中存在不同类型的硝态氮受体,可以感受外界硝态氮浓度变化,并启用高亲和力或低亲和力硝态氮吸收系统,从而吸收硝态氮;硝态氮进入根系后,大部分被运输到地上部进行同化作用,合成大分子物质,以促进植物生长;如果地上部硝态氮含量过多,植物可把多余的硝态氮运送到液泡内储存,待需要时再从液泡转运至细胞质中利用。植物生长发育过程中,老叶和成熟叶片中的硝态氮可被转运到新生组织中,促进新生组织生长。硝态氮吸收利用过程中大量硝态氮吸收、转运、储存、同化和信号调控基因被有序激活并协调工作,促进植物高效吸收利用硝态氮。本文主要针对NRT1和NRT2硝态氮吸收转运相关基因及其功能,以及参与初级硝态氮反应的相关转录因子和小信号多肽在硝态氮信号传导和组织间的信号交流进行综述,以便深入理解植物吸收利用硝态氮的机理,为高效利用氮素的作物育种和栽培技术的创建提供新的思路。     

土壤氨基酸生物有效性及其环境调控研究进展

土壤中种类繁多的小分子和大分子有机氮,是土壤氮素的重要组成成分。大多数植物可以直接吸收氨基酸乃至多肽和蛋白质,不是完全需要经过传统理论认知的微生物分解为无机氮的过程。植物根系具有吸收、转运和代谢外源吸收的有机氮的能力。土壤微生物是植物根系有机氮的主要竞争者,不同土壤中,参与竞争的微生物组成存在较大差异。环境对植物根系吸收和后续代谢有机氮都具有重要的调控作用。未来应着重于精准定量化分析土壤有机氮组成及含量,确定土壤有机氮对植物生长的长期效应,探索环境变化尤其是复杂环境变化对植物吸收利用有机氮的影响及其关键步骤,进一步确定土壤有机氮对植物氮营养的贡献。     

植物营养分子遗传研究进展

过去10年间,在植物矿质养分吸收利用与养分胁迫诱导调节机理分于生物学方面的研究进展使我们对植物营养分子遗传背景有了新的了解。本文对有关养分转运子基因克隆,养分胁迫诱导调节机理,应用分子标记技术研究养分吸收利用遗传背景等方而的研究进展及方法作一介绍。     

机理Ⅰ植物铁营养的吸收转运及信号调控机制研究进展

铁是植物正常生长发育必需的微量元素之一。在通气良好的碱性或石灰性土壤中,常常因铁有效性低而难以满足植物生长发育所需,缺铁已成为继缺氮和缺磷之后农业生产所面临的又一重要的营养障碍因子。与机理Ⅱ植物相比,机理Ⅰ植物更易缺铁,因此全面了解机理Ⅰ植物的铁吸收及利用机制是分子育种改良此类植物铁营养的重要基础。基于国内外的相关研究进展,从机理Ⅰ植物的根际铁活化、根系铁吸收、木质部和韧皮部中的铁运输以及胞外和胞内铁的再利用等几方面进行综述;在此基础上,从bHLH和MYB转录因子调控网络、蛋白的泛素化修饰以及小分子化学信号调控途径等几方面,重点阐述机理Ⅰ植物铁营养吸收、转运及稳态平衡过程的调控机制;同时,对研究中存在的部分问题及未来研究方向进行简要的讨论分析。     

植物钾吸收的分子水平研究

本文从钾离子通道、高亲和力K+ 转运体和H+ -ATP酶等 3方面综述了K+营养的分子生物学、生理生化等的研究结果。植物钾吸收与这 3类转运蛋白的关系极为密切。主要论述K+转运体和K+通道及其介导高低亲和力钾吸收方面的作用 ,以及 3类转运蛋白的调节 ,蛋白的表达 ,调节影响K+的吸收运输和利用     

Controls over mycorrhizal uptake of organic nitrogen

Mycorrhizal plants from a variety of ecosystems have the capacity to take up organic forms of nitrogen, yet the fraction of plant nitrogen demand met by organic N (ON) uptake remains unclear. ON uptake by mycorrhizal plants is a biochemical process that involves multiple steps, including breakdown and uptake of soil ON by mycorrhizal fungi, internal transformation of ON, and transfer of N to the host plant. We present hypothetical mechanisms controlling each of these steps and outline predictions for how these mechanisms structure patterns of ON uptake by mycorrhizal plants in ecosystems. Using a synthesis of published data, we found that uptake of amino acids by mycorrhizal fungi is related to the relative abundance, N content, and carbon structure of the amino acid. We hypothesize that the bond strength and structural diversity of soil ON controls the breakdown of polymeric ON by mycorrhizal fungi. In addition, the availability of carbon resources for the mycorrhizal fungus influences the capacity for mycorrhizal fungi to assimilate amino acids and produce extracellular enzymes that catalyze the breakdown of polymeric ON.     

The effect of amino acids and amides on the regulation of nitrate uptake by wheat seedlings

Wheat plants grown hydroponically increased their nitrate uptake rate more than two‐fold after three days of N starvation. Exogenously supplied amino acids and amides had no effect on the nitrate uptake rate of plants well nourished in N. After three days of N starvation, however, some of the amino acids and amides supplied to plants inhibited up to 50% of the nitrate uptake rate. The most effective inhibitor was aspartic acid. Asparagine, glutamine or phenylalanine did not show any inhibitory effect. The percentage of inhibition was not increased by increasing the amino acid concentration, nor did the addition of mixed amino acids and amides increase the inhibition exerted by one amino acid alone. During the three days of N starvation, there was a decrease in the concentration of endogenous amino acids in the roots, but not all amino acids decreased their concentration at the same rate.

It is suggested that the endogenous levels of some amino acids may repress the nitrate uptake system in plants well supplied with N. During the development of the N deficiency, the concentration of these amino acid decreases, de‐repressing the nitrate uptake system.     

Effects of nitrogen rate and nitrogen form on glycine uptake by pakchoi (Brassica chinensis L.) under sterile culture

It is well known that plants are capable of taking up intact amino acids. However, how the nitrogen (N) rates and N forms affect amino acid uptake and amino acid nutritional contribution for plant are still uncertain. Effects of the different proportions of nitrate (NO₃^?), ammonium (NH₄⁺) and ¹⁵N-labeled glycine on pakchoi seedlings glycine uptake were investigated for 21 days hydroponics under the aseptic media. Our results showed that plant biomass and glycine uptake was positively related to glycine rate. NO₃^? and NH₄⁺, the two antagonistic N forms, both significantly inhibited plant glycine uptake. Their interactions with glycine were also negatively related to glycine uptake and glycine nutritional contribution. Glycine nutritional contribution in the treatments with high glycine rate (13.4%–35.8%) was significantly higher than that with low glycine rate (2.2%–13.2%). The high nutritional contribution indicated amino acids can serve as an important N source for plant growth under the high organic and low inorganic N input ecosystem.     

Do plant species with different growth strategies vary in their ability to compete with soil microbes for chemical forms of nitrogen?

We used dual labelled stable isotope (¹³C and ¹⁵N) techniques to examine how grassland plant species with different growth strategies vary in their ability to compete with soil microbes for different chemical forms of nitrogen (N), both inorganic and organic. We also tested whether some plant species might avoid competition by preferentially using different chemical forms of N than microbes. This was tested in a pot experiment where monocultures of five co-existing grassland species, namely the grasses Agrostis capillaris, Anthoxanthum odoratum, Nardus stricta, Deschampsia flexuosa and the herb Rumex acetosella, were grown in field soil from an acid semi-natural temperate grassland. Our data show that grassland plant species with different growth strategies are able to compete effectively with soil microbes for most N forms presented to them, including inorganic N and amino acids of varying complexity. Contrary to what has been found in strongly N limited ecosystems, we did not detect any differential uptake of N on the basis of chemical form, other than that shoot tissue of fast-growing plant species was more enriched in ¹⁵N from ammonium-nitrate and glycine, than from more complex amino acids. Shoot tissue of slow-growing species was equally enriched in ¹⁵N from all these N forms. However, all species tested, least preferred the most complex amino acid phenylalanine, which was preferentially used by soil microbes. We also found that while fast-growing plants took up more of the added N forms than slow-growing species, this variation was not related to differences in the ability of plants to compete with microbes for N forms, as hypothesised. On the contrary, we detected no difference in microbial biomass or microbial uptake of ¹⁵N between fast and slow-growing plant species, suggesting that plant traits that regulate nutrient capture, as opposed to plant species-specific interactions with soil microbes, are the main factor controlling variation in uptake of N by grassland plant species. Overall, our data provide insights into the interactions between plants and soil microbes that influence plant nitrogen use in grassland ecosystems.     

木本植物适应酸性土壤机理的研究进展——以胡枝子(Lespedeza bicolor)和油茶(Camellia oleifera)为例

综述了近年来木本植物适应酸性土壤的耐铝机理研究进展,重点以酸性土壤先锋植物胡枝子(Lespedeza bicolor)和铝累积植物油茶(Camellia oleifera)为例,总结了木本植物根系有机酸的分泌、铝吸收和运输机制及铝与氮磷胁迫的协同适应等。木本植物有铝累积和铝排斥植物之分;铝排斥植物胡枝子耐铝的重要机制是其根系同时分泌柠檬酸和苹果酸;铝累积植物油茶高效累积铝的原因在于其不仅可以高效吸收土壤和土壤溶液中广泛存在的铝(Al3+和Al-F),而且可以通过木质部运输和特定季节韧皮部运输的配合实现铝的高效分配和传输;铵态氮相对于硝态氮可缓解胡枝子的铝毒害;磷对不同胡枝子耐铝作用的影响明显不同。木本植物适应酸性土壤机理的深入研究将会有助于完善植物的耐铝机理及铝运输理论,并为酸性土壤中矿质养分管理提供理论基础。     

Variation in competitive abilities of plants and microbes for specific amino acids

 Microbes are assumed to possess strong competitive advantages over plants for uptake of nutrients from the soil. The finding that non-mycorrhizal plants can obtain a significant fraction of their N requirement from soil amino acids contradicts this assumption. The amino acid glycine (Gly) has been used as a model amino acid in many recent studies. Our preliminary studies showed that Gly was a poor substrate for microbial growth compared to other amino acids. We tested the hypothesis that the alpine sedge Kobresia myosuroides competes better for Gly than for other amino acids because of decreased microbial demand for this compound. Soil microbial populations that could grow using Gly as a sole carbon source were about 5 times lower than those that could grow on glutamate (Glu). Gly supported a significantly lower population than any of the ten other amino acids tested except serine. In contrast, K. myosuroides took up Gly from hydroponic solution at faster rates than Glu. In plant-soil microcosms, plants competed with soil microbes 3.25 times better for Gly than for Glu. We conclude that the low microbial demand and the rapid plant uptake of Gly relative to other amino acids allow Gly to be an especially important nitrogen source for K. myosuroides. Received: 9 February 1998     

Uptake,assimilation and transport of nitrogen compounds by plants

This paper reviews current knowledge and presents some new information on the metabolism of nitrogen in various species of higher plants.The role of the root system is considered. It is shown that the roots of many herbaceous and woody plants can manufacture organic compounds of nitrogen from the nitrate or other forms of inorganic nitrogen they absorb from the medium. The extent to which they do this varies greatly with the age and nutrition of the plant and with the environmental conditions under which it is growing. The relationship is examined between the synthetic activities of the root and its activity in upward transport of nitrogen to the shoot. The latter process takes place predominantly, if not exclusively, in the xylem, and in each species one or more nitrogen-rich compounds, e.g., amides, ureides and amino acids, carry the bulk of the nitrogen leaving the root. A second group of plants is described in which roots do not function to any extent in the reduction of nitrate.Consideration is given to the fate of recently absorbed nitrogen once it reaches the shoot system. An inorganic source such as nitrate, or molecules such as amides containing surplus amino groupings, are shown to serve as nitrogen sources for synthesis of amino acids required for protein synthesis. Some of these amino acids arise directly from the photosynthetic apparatus. Alternatively, surplus nitrogen arriving from the root may be stored in the shoot, from where it is drawn upon extensively if uptake by the root fails to keep pace with the shoot's demands for nitrogen.The transport system for nitrogen is examined for the whole plant. The classes of sources and sinks for nitrogen are described, and information presented on the types of nitrogenous solutes they receive from the xylem and phloem.