植物苹果酸和柠檬酸通道蛋白基因的研究进展

铝毒是酸性土壤中抑制植物生长和减少作物产量的主要因素。近年来研究表明植物主要通过根部有机酸通道蛋白将小分子有机酸阴离子转运到细胞膜外来缓解铝毒。本文综述了植物中编码铝诱导的苹果酸转运蛋白和多药及毒性复合物的排出转运蛋白两种耐铝基因,并从基因克隆、蛋白质同源性比较、基因表达调控、基因的功能和应用以及预测耐铝基因作用模式等方面进行了阐述;同时对这些耐铝基因的应用前景进行了展望。     

植物铝胁迫响应基因的研究进展

铝毒是酸性土壤中植物生长和作物生产的主要限制因子.近年来的很多研究应用差异显示PCR、抑制差减cDNA文库和DNA微正列等技术,在一些铝耐受型和敏感型植物中鉴定了很多铝胁迫响应基因.本研究通过参阅国内外有关报道和结合本实验室的研究成果,从铝诱导的通道蛋白、代谢相关、胁迫和细胞死亡以及信号转导相关基因4个方面的研究进展进行了综述.     

植物ABC转运蛋白及其在Al胁迫下的功能研究进展

ABC(ATP-Binding Cassette)转运蛋白家族是目前已知最大、功能最广泛的蛋自家族,能利用水解ATP的能量来参与生物体内多种物质的转运,这一基因家族成员在哺乳动物和微生物中已广泛鉴定,在植物中的研究是一个相对较新的研究领域.铝是酸性土壤作物生产的一个主要的限制因素,ABC转运蛋白在植物铝耐受性方面有重要作用.该文主要对ABC转运蛋白的特点、生物学功能及植物ABC转运蛋白在Al胁迫下的作用进行了综述,并分析其存在的问题,展望今后可能开展的研究方向.     

植物镉忍耐的分子机理

Cd是植物非必需的微量元素,对植物有很强的毒性.Cd抑制植物细胞生长,抑制氧化磷酸化,引发氧化胁迫,影响光合作用,损伤核仁和影响质膜ATP酶的活力.一些耐Cd植物通过诱导形成螯合肽、金属硫蛋白、植物应激蛋白等抵御Cd毒,也有的耐Cd植物则通过细胞壁固定、液泡分隔、腺体分泌等途径来抵御Cd毒.植物螯合肽合成酶(PCS)相关的一些基因已得到克隆.金属硫蛋白(MT)的克隆基因导入植物,使植物对Cd毒的抗性增加;植物胁迫蛋白可提高植物对Cd毒的抗性,Zn转运蛋白可运转Cd.修饰基因则通过影响主要基因提高植物对Cd的忍耐能力.野生型植物耐Cd毒是多基因控制的,而植物短期的Cd忍耐,则仅受一个或少数基因控制.     

植物Na+/H+反向转运蛋白的研究进展

盐胁迫是限制植物生长发育的主要因素之一,植物Na+/H+反向转运蛋白可通过将Na+逆向转运出细胞外或将Na+区隔化于液泡中来抵制环境中过高的Na+浓度.植物中Na+/H+反向转运蛋白存在于细胞质膜和液泡膜上,现在已得到多种编码这些Na+/H+反向转运蛋白的基因,对其结构功能特性进行了大量研究,并发现将这些基因转入非抗盐植物中过量表达可提高转基因植物的抗盐性.概述了Na+/H+反向转运蛋白及其编码基因的最新研究进展.     

铝胁迫下植物根系的有机酸分泌及其解毒机理

酸性土壤中的铝毒害问题,已成为限制植物生长发育的主要因素之一.耐铝植物通过根系分泌有机酸来解除或减轻铝的毒害是外部解铝毒的重要机制.文章对铝胁迫下植物根系分泌有机酸的种类,有机酸解铝毒机理、解铝毒能力,有机酸分泌方式及调控其分泌的主要因素等相关研究进行综述.     

植物重金属转运蛋白研究进展

土壤中的有毒重金属不仅对植物有害,也可通过食物链危害人类和动物的健康.重金属转运蛋白在植物吸收、抵抗重金属的复杂机制中起着关键作用.植物重金属转运蛋白分为吸收蛋白和排出蛋白,其中,吸收蛋白转运必需重金属进入细胞,同时也会因为必需重金属的缺乏或离子之间的竞争而运载有毒重金属;排出蛋白是一类解毒蛋白,可将过量的或有毒的重金属逆向转运出细胞,或区室化于液泡中.目前,细胞内多种重金属转运蛋白基因的转录水平与重金属离子积累之间的联系已被揭示,并分离克隆出诸多相关蛋白家族成员.本文综述了近年来发现并鉴定的主要重金属转运蛋白的金属亲和性、器官表达特异性及细胞内定位等的研究进展.     

生长素及其运输蛋白对植物铝胁迫的响应

铝对植物的毒害作用主要表现为抑制根尖生长,而根尖生长与生长素及其运输密切相关,铝可能影响了生长素及其代谢过程,但目前尚不清楚生长素及其运输蛋白如何参与植物应对铝胁迫响应。本文通过分析、总结前人研究,并结合自己的前期研究结果,初步阐述生长素或其运输蛋白对植物铝胁迫的响应,即铝影响生长素代谢的相关基因,干扰根尖生长素运输蛋白在细胞内分布及其囊泡运输,调控生长素的极性运榆,进而抑制根尖生长。另一方面,生长素或其运输蛋白又参与了植物应对铝胁迫过程,这主要体现在参与了植物铝毒信号传递、根系铝内置化过程和减缓铝诱导的氧化胁迫。最后,本文提出了生长素及其运输蛋白对植物铝胁迫响应的可能模型。     

植物对锰的吸收运输及对过量锰的抗氧化响应

锰（Mn）毒是酸性土壤上限制作物生长的重要因素。植物体内Mn^2＋吸收运输的转运蛋白或将Mn^2＋分隔储存于内膜细胞器（如液泡）中,或在细胞内Mn^2＋运输及调节中起重要作用。近年,编码这些转运蛋白的基因已被分离鉴定。另外,高Mn胁迫极易诱导植物产生氧化胁迫,抗氧化系统在清除高蝴迫诱导产生的活性氧过程中起到重要作用。文章重点就承担Mn^2＋跨膜运输的膜转运蛋白以及植物抗氧化系统对高蝴迫的响应两方面进行了综述,并结合作者的研究提出看法和展望。     

植物适应铝毒胁迫的生理及分子生物学机理

铝毒是酸性土壤上限制作物生长最重要的因素,严重影响着全世界和中国大约40％和21％耕作土壤的作物生产．近几十年来,世界各国针对植物的铝毒及其耐铝机制进行了大量的研究,并取得了较大进展．文中重点综述了植物适应铝胁迫基因型差异筛选方法及其鉴定技术、植物适应铝胁迫的生理基础及分子生物学机制等方面的研究进展,简要讨论了今后的研究方向．     

The roles of organic anion permeases in aluminium resistance and mineral nutrition

Soluble aluminium (Al(3+)) is the major constraint to plant growth on acid soils. Plants have evolved mechanisms to tolerate Al(3+) and one type of mechanism relies on the efflux of organic anions that protect roots by chelating the Al(3+). Al(3+) resistance genes of several species have now been isolated and found to encode membrane proteins that facilitate organic anion efflux from roots. These proteins belong to the Al(3+)-activated malate transporter (ALMT) and multi-drug and toxin extrusion (MATE) families. We review the roles of these proteins in Al(3+) resistance as well as their roles in other aspects of mineral nutrition.     

Maize ZmALMT2 is a root anion transporter that mediates constitutive root malate efflux

Root efflux of organic acid anions underlies a major mechanism of plant aluminium (Al) tolerance on acid soils. This efflux is mediated by transporters of the Al-activated malate transporter (ALMT) or the multi-drug and toxin extrusion (MATE) families. ZmALMT2 was previously suggested to be involved in Al tolerance based on joint association-linkage mapping for maize Al tolerance. In the current study, we functionally characterized ZmALMT2 by heterologously expressing it in Xenopus laevis oocytes and transgenic Arabidopsis. In oocytes, ZmALMT2 mediated an Al-independent electrogenic transport product of organic and inorganic anion efflux. Ectopic overexpression of ZmALMT2 in an Al-hypersensitive Arabidopsis KO/KD line lacking the Al tolerance genes, AtALMT1 and AtMATE, resulted in Al-independent constitutive root malate efflux which partially restored the Al tolerance phenotype. The lack of correlation between ZmALMT2 expression and Al tolerance (e.g., expression not localized to the root tip, not up-regulated by Al, and higher in sensitive versus tolerance maize lines) also led us to question ZmALMT2's role in Al tolerance. The functional properties of the ZmALMT2 transporter presented here, along with the gene expression data, suggest that ZmALMT2 is not involved in maize Al tolerance but, rather, may play a role in mineral nutrient acquisition and transport.     

Natural variation of <Emphasis Type="Italic">Arabidopsis thaliana </Emphasis>reveals that aluminum resistance and proton resistance are controlled by different genetic factors

Root growth of Arabidopsis thaliana is inhibited by proton rhizotoxicity in low ionic strength media when the pH of the medium is lower than 5.0. QTL analysis at pH 4.7 revealed that two major QTLs on chromosome 2 and 5 and an additional six epistatic interacting loci pairs control proton resistance in the Ler/Col recombinant inbred population. These genetic factors are independently associated with proton resistance in comparison to the known Al resistant QTL and epistases detected in the same RI population at 4 μM Al at pH 5.0. This indicates that different genetic factors regulate mechanisms of resistance to each stress in this plant species. No correlation was observed between proton resistance and Al resistance among 260 accessions indicating that there is no simple relationship between the genetic factors controlling each trait. Several accessions with different combinations of proton (pH 4.7) and Al (4 μM Al at pH 5.0) resistances were identified by phenotypic cluster analysis. Although this grouping was performed using root growth data, the degree of resistance was correlated with their sensitivity to short-term damage in the root tip, indicating that the same resistance mechanism controls proton resistance at different time scales. Resistant accessions grew better than sensitive ones in acid soil culture. This suggests that proton resistance in hydroponic conditions could be an important index in breeding programs to improve productivity in acid soil, at least in acid sensitive plant species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Molecular and physiological strategies to increase aluminum resistance in plants

Aluminum (Al) toxicity is a primary limitation to plant growth on acid soils. Root meristems are the first site for toxic Al accumulation, and therefore inhibition of root elongation is the most evident physiological manifestation of Al toxicity. Plants may resist Al toxicity by avoidance (Al exclusion) and/or tolerance mechanisms (detoxification of Al inside the cells). The Al exclusion involves the exudation of organic acid anions from the root apices, whereas tolerance mechanisms comprise internal Al detoxification by organic acid anions and enhanced scavenging of free oxygen radicals. One of the most important advances in understanding the molecular events associated with the Al exclusion mechanism was the identification of the ALMT1 gene (Al-activated malate transporter) in Triticum aestivum root cells, which codes for a plasma membrane anion channel that allows efflux of organic acid anions, such as malate, citrate or oxalate. On the other hand, the scavenging of free radicals is dependent on the expression of genes involved in antioxidant defenses, such as peroxidases (e.g. in Arabidopsis thaliana and Nicotiana tabacum), catalases (e.g. in Capsicum annuum), and the gene WMnSOD1 from T. aestivum. However, other recent findings show that reactive oxygen species (ROS) induced stress may be due to acidic (low pH) conditions rather than to Al stress. In this review, we summarize recent findings regarding molecular and physiological mechanisms of Al toxicity and resistance in higher plants. Advances have been made in understanding some of the underlying strategies that plants use to cope with Al toxicity. Furthermore, we discuss the physiological and molecular responses to Al toxicity, including genes involved in Al resistance that have been identified and characterized in several plant species. The better understanding of these strategies and mechanisms is essential for improving plant performance in acidic, Al-toxic soils.     

The ScAACT1 gene at the Q alt5 locus as a candidate for increased aluminum tolerance in rye (Secale cereale L.)

Soluble aluminum (Al³⁺) is a major constraint to plant growth in highly acidic soils, which comprise up to 50% of the world??s arable land. The primary mechanism of Al resistance described in plants is the chelation of Al³⁺ cations by release of organic acids into the rhizosphere. Candidate aluminum tolerance genes encoding organic acid transporter of the ALMT (aluminum-activated malate transporter) and MATE (multi-drug and toxic compound extrusion) families have been characterized in several plant species. In this study, we have isolated in five different cultivars the rye ScAACT1 gene, homolog to barley aluminum activated citrate transporter HvAACT1. This gene mapped to the 7RS chromosome arm, 25?cM away from the ScALMT1 aluminum tolerance gene. The gene consisted of 13 exons and 12 introns and encodes a predicted membrane protein that contains the MatE domain and at least seven putative transmembrane regions. Expression of the ScAACT1 gene is Al-induced, but there were differences in the levels of expression among the cultivars analyzed. A new quantitative trait locus for Al tolerance in rye that co-localizes with the ScAACT1 gene was detected in the 7RS chromosome arm. These results suggest that the ScAACT1 gene is a candidate gene for increased Al tolerance in rye. The phylogenetic relationships between different MATE proteins are discussed.