植物质膜蛋白质组的逆境应答研究进展

质膜作为原生质体与外界环境的屏障, 除了维持正常的细胞内稳态和营养状况, 还参与感知和应答各种环境胁迫。近年来, 植物质膜蛋白质组学研究为深入分析植物应答不同生物和非生物胁迫的分子机制提供了重要信息, 已经报道了模式植物拟南芥(Arabidopsis thaliana)和水稻(Oryza sativa)等10种植物质膜应对生物胁迫(白叶枯病菌(Xanthomonas oryzae pv. oryzae)感染)与非生物胁迫(冷、盐、水淹、渗透、高pH值、Fe缺乏及过量、氮素、脱落酸、壳聚糖和壳寡糖)过程的蛋白质丰度模式变化。通过整合分析植物质膜响应逆境的蛋白质组学研究结果, 揭示了质膜在植物应答逆境胁迫过程中的重要作用。植物通过调节转运蛋白、通道蛋白及膜泡运输相关蛋白的丰度变化促进细胞内外的信号传递、物质交换与运输; 同时利用膜相关的G蛋白、Ca²⁺信号、磷酸肌醇信号途径及BR信号途径等多种信号通路, 通过蛋白质可逆磷酸化作用感知和传递胁迫信号, 调节植物抵御胁迫。研究结果为从蛋白质水平认识质膜逆境应答分子调控机制提供了新线索。     

过氧化氢酶在植物生长发育和胁迫响应中的功能研究进展

过氧化氢酶(catalase, CAT)作为过氧化氢(hydrogen peroxide, H₂O₂)的清除酶在植物生长发育和胁迫响应中扮演着十分重要的角色。CAT的功能受到严格调控,其在正常条件下维持适当浓度的H₂O₂作为信号分子以保证植物的生长发育;在胁迫下保持H₂O₂稳态以增强植物耐逆性。本文对近年来CAT在植物生长发育和胁迫响应中的功能研究进展予以综述,特别是翻译后修饰和亚细胞定位对CAT功能的调控,并对植物CAT的调控机理研究进行了展望。     

解析植物冷信号转导途径: 植物如何感知低温

低温胁迫(冷害和冻害)严重影响植物的生长发育和地理分布, 是制约作物产量和品质的主要因素之一。在自然界, 植物通过感知低温信号并启动一系列响应机制来抵御冷冻伤害。MAP蛋白激酶家族在植物响应逆境胁迫信号过程中发挥重要作用, 但其是否参与冷冻胁迫信号传递仍不清楚。最近, 朱健康、杨淑华和种康研究团队先后报道了拟南芥(Arabidopsis thaliana)和水稻(Oryza sativa)通过MAPK级联反应途径参与冷冻胁迫应答反应, 通过磷酸化ICE1来调控其稳定性, 并阐明了ICE1提高植物抗冷冻能力的分子机制。他们的研究完善了ICE1介导的低温应答网络, 是植物低温应答研究领域的重要突破, 并为未来的作物分子设计育种提供了强有力的理论依据。     

白桦BpZFP4基因启动子克隆和逆境响应元件功能分析

前期研究发现白桦锌指蛋白BpZFP4基因响应多种非生物逆境胁迫。为了深入研究其调控机制,本研究利用染色体步移技术克隆了该基因上游1 360 bp的启动子区域,序列分析结果表明该区域含有多个逆境响应顺式作用元件、激素响应元件、光响应以及病原菌和损伤响应元件等。在此基础上,构建了BpZFP4启动子5'-端一系列缺失片段融合GUS报告基因的表达载体。通过对系列缺失突变体在正常条件以及渗透胁迫、盐胁迫和脱落酸（ABA）处理条件下的GUS基因表达分析,鉴定得到BpZFP4启动子对干旱、盐和ABA应答响应的主要调节区域及可能的顺式作用元件。本研究结果为进一步探究BpZFP4基因应答非生物胁迫和信号分子刺激的调控机理提供了重要的理论依据。     

m6A修饰在植物生长发育和抗逆境胁迫中的功能

真核生物mRNA存在多种甲基化修饰,其中N⁶-腺苷酸甲基化(N⁶-methyladenosine, m⁶A)修饰是最为常见的一种动态内部修饰。m⁶A是指RNA腺嘌呤的第6位氮原子上发生甲基化修饰,它能够动态的被甲基转移酶添加,被去甲基化酶去除,以及被甲基化阅读蛋白识别。近年来,植物m⁶A修饰相关的酶被陆续鉴定,研究发现m⁶A修饰调控植物胚胎发育、茎尖分生组织分化、开花等生长发育过程,在植物抗逆境胁迫响应中也具有重要调控作用。本文就m⁶A修饰相关酶的组成及其在植物生长发育和植物抗逆境胁迫过程中的功能相关研究进展进行综述,并对甘蓝型油菜中m⁶A修饰相关的酶进行了生物信息学分析。     

过表达兴安落叶松TPP基因增强拟南芥对盐胁迫的耐受能力*

兴安落叶松(Larix gmelinii)是极为重要的造林针叶树种,具有早期速生、抗逆性强、生态效益好等特点。海藻糖参与调控干旱、寒冷、盐害等多种逆境胁迫,海藻糖-6-磷酸磷酸酶(TPP)是海藻糖合成通路的重要酶。从兴安落叶松逆境胁迫转录组中筛选到LgTPPI.1基因全长序列,克隆了其编码区(CDS),构建了重组载体并获得过表达LgTPPI.1拟南芥纯合株系。结果表明,LgTPPI.1 CDS全长1 236 bp,共编码411个氨基酸;LgTPPI.1基因的mRNA在根和茎中表达水平较低,在针叶中表达水平较高;过表达LgTPPI.1基因拟南芥在盐胁迫下海藻糖含量显著提高、脯氨酸和抗氧化酶类活性增加、胁迫响应标记基因表达上调、对盐胁迫的耐受性增强。这些结果表明,裸子植物利用与被子植物类似的海藻糖通路来耐受非生物胁迫。为后续进一步解析落叶松中海藻糖合成相关基因的功能,揭示裸子植物中针叶树对逆境的响应机制奠定基础。     

非生物胁迫相关NAC转录因子的结构及功能

NAC是植物特有的一类转录因子,参与植物多个生长发育过程,还参与植物对逆境胁迫的响应。本文对非生物胁迫相关NAC转录因子的结构特征、功能预测、表达特性、在转基因植物中的作用及调控路径进行综述。非生物胁迫相关NAC转录因子具有典型的NAc胁迫亚家族结构特征,根据这些结构特征可以预测其功能;非生物胁迫相关NAc转录因子能响应多种非生物胁迫,其转基因过表达大多能使转基因植物提高一种或几种胁迫耐受性;非生物胁迫相关NAc转录因子有着复杂的调控路径。这些NAc转录因子可用于提高转基因植物的逆境耐受性。     

油菜素甾醇调控水稻盐胁迫应答的作用研究

油菜素甾醇(BR)作为植物内源激素, 广泛参与植物的生长发育过程及逆境应答。虽然BR调控生长发育的分子机制目前已相对清楚, 但在水稻(Oryza sativa)中, BR在逆境反应中的功能还鲜有报道。该研究系统分析了BR在高盐胁迫过程中的作用, 表明盐胁迫和逆境激素脱落酸可抑制BR合成基因D2和D11的表达, 典型的BR缺陷突变体(如d2-2和d61-1)则表现出对盐胁迫敏感性增强。此外, 通过对BR核心转录因子OsBZR1的过表达株系进行分析, 发现BR可显著诱导OsBZR1的去磷酸化, 盐胁迫对OsBZR1蛋白的积累水平和磷酸化状态均有调控作用。转录组数据分析表明, BR处理前后差异表达基因中有38.4%同时受到盐胁迫调控, 其中91.5%受到BR和高盐一致调控, 并显著富集在应激反应过程中。研究结果表明, BR正调控水稻的耐盐性, 而盐胁迫通过抑制BR合成来限制水稻的生长。     

植物甾醇在植物逆境胁迫中的研究进展

植物甾醇是一类重要的生理活性物质,对植物的生长发育具有重要作用,对响应植物逆境胁迫也具有重要功能.植物甾醇是细胞膜和脂质筏的重要组分,与膜的稳定性密切相关,主要通过甾醇含量的相对变化维持膜的稳定性及影响脂质筏的生物功能响应逆境胁迫.植物甾醇作为信号分子参与逆境胁迫中的信号传导,油菜素内酯类(BRs)是植物甾醇合成途径的重要产物,作为一种重要的信号分子调控植物甾醇合成酶基因的表达以响应逆境胁迫.     

木薯MeMYC2.2基因耐低温功能研究

MYC2（MYeloCytomatosis）转录因子是植物应对逆境胁迫过程中茉莉酸信号传导相关的核心转录因子。本研究旨在初步分析木薯MeMYC2.2基因在低温胁迫响应中的功能。利用生物信息学分析木薯MeMYC2.1和MeMYC2.2基因的结构及其编码蛋白的理化性质;通过定量PCR分析了上述2个基因在木薯组培苗叶片中对低温胁迫的响应;通过转基因拟南芥研究MeMYC2.2的抗冻功能。木薯组培苗叶片中2个MeMYC2基因的表达均在低温胁迫早期被诱导,其中,与MeMYC2.1相比,MeMYC2.2差异表达更显著。MeMYC2.2蛋白主要定位于细胞核中,且在酵母中具有明显转录自激活功能,表明该蛋白具有转录因子特性。与野生型相比,过表达MeMYC2.2的转基因拟南芥抗冻能力显著提高。在低温处理下,CBF3基因在转基因拟南芥中的表达量要明显高于其在野生型的表达量,但另外3个CBF基因在转基因拟南芥中的表达量明显下降。木薯MeMYC2.2的表达受低温和茉莉酸调控,可以提高植物的抗冻性,且可能影响CBF基因对低温的响应。本研究为进一步利用MeMYC2基因改良木薯的低温耐受性奠定了理论基础。     

The nucleotidase/phosphatase SAL1 is a negative regulator of drought tolerance in Arabidopsis

An Arabidopsis thaliana drought-tolerant mutant, altered expression of APX2 ( alx8 ), has constitutively increased abscisic acid (ABA) content, increased expression of genes responsive to high light stress and is reported to be drought tolerant. We have identified alx8 as a mutation in SAL1, an enzyme that can dephosphorylate dinucleotide phosphates or inositol phosphates. Previously identified mutations in SAL1, including fiery ( fry1-1 ), were reported as being more sensitive to drought imposed by detachment of rosettes. Here we demonstrate that alx8 , fry1-1 and a T-DNA insertional knockout allele all have markedly increased resistance to drought when water is withheld from soil-grown intact plants. Microarray analysis revealed constitutively altered expression of more than 1800 genes in both alx8 and fry1-1. The up-regulated genes included some characterized stress response genes, but few are inducible by ABA. Metabolomic analysis revealed that both mutants exhibit a similar, dramatic reprogramming of metabolism, including increased levels of the polyamine putrescine implicated in stress tolerance, and the accumulation of a number of unknown, potential osmoprotectant carbohydrate derivatives. Under well-watered conditions, there was no substantial difference between alx8 and Col-0 in biomass at maturity; plant water use efficiency (WUE) as measured by carbon isotope discrimination; or stomatal index, morphology or aperture. Thus, SAL1 acts as a negative regulator of predominantly ABA-independent and also ABA-dependent stress response pathways, such that its inactivation results in altered osmoprotectants, higher leaf relative water content and maintenance of viable tissues during prolonged water stress.     

Insertion of a Specific Fungal 3′-phosphoadenosine-5′-phosphatase Motif into a Plant Homologue Improves Halotolerance and Drought Tolerance of Plants

Soil salinity and drought are among the most serious agricultural and environmental problems of today. Therefore, investigations of plant resistance to abiotic stress have received a lot of attention in recent years. In this study, we identified the complete coding sequence of a 3′-phosphoadenosine-5′-phosphatase protein, ApHal2, from the halotolerant yeast Aureobasidium pullulans. Expression of the ApHAL2 gene in a Saccharomyces cerevisiae hal2 mutant complemented the mutant auxotrophy for methionine, and rescued the growth of the hal2 mutant in media with high NaCl concentrations. A 21-amino-acids-long region of the ApHal2 enzyme was inserted into the Arabidopsis thaliana homologue of Hal2, the SAL1 phosphatase. The inserted sequence included the META motif, which has previously been implicated in increased sodium tolerance of the Hal2 homologue from a related fungal species. Transgenic Arabidopsis plants overexpressing this modified SAL1 (mSAL1) showed improved halotolerance and drought tolerance. In a medium with an elevated salt concentration, mSAL1-expressing plants were twice as likely to have roots in a higher length category in comparison with the wild-type Arabidopsis and with plants overexpressing the native SAL1, and had 5% to 10% larger leaf surface area under moderate and severe salt stress, respectively. Similarly, after moderate drought exposure, the mSAL1-expressing plants showed 14% increased dry weight after revitalisation, with no increase in dry weight of the wild-type plants. With severe drought, plants overexpressing native SAL1 had the worst rehydration success, consistent with the recently proposed role of SAL1 in severe drought. This was not observed for plants expressing mSAL1. Therefore, the presence of this fungal META motif sequence is beneficial under conditions of increased salinity and moderate drought, and shows no drawbacks for plant survival under severe drought. This demonstrates that adaptations of extremotolerant fungi should be considered as a valuable resource for improving stress-tolerance in plant breeding in the future.     

The root of ABA action in environmental stress response

The growth and development of plants are influenced by the integration of diverse endogenous and environmental signals. Acting as a mediator of extrinsic signals, the stress hormone, abscisic acid (ABA), has been shown to regulate many aspects of plant development in response to unfavourable environmental stresses, allowing the plant to cope and survive in adverse conditions, such as drought, low or high temperature, or high salinity. Here, we summarize recent evidence on the roles of ABA in environmental stress responses in the Arabidopsis root; and on how ABA crosstalks with other phytohormones to modulate root development and growth in Arabidopsis. We also review literature findings showing that, in response to environmental stresses, ABA affects the root system architecture in other plant species, such as rice.     

油菜素内酯调控作物农艺性状和非生物胁迫响应的研究进展

植物对不利环境的适应依赖于将外部胁迫信号传递到内部信号通路中,在进化过程中形成一系列的胁迫响应机制。其中,油菜素内酯(brassinosteroids, BRs)是一种类固醇激素,广泛参与植物生长发育和逆境响应过程。BRs被包括受体BRI1和共受体BAK1在内的细胞表面受体感知,继而触发信号级联,导致蛋白激酶BIN2的抑制和转录因子BES1/BZR1的激活,BES1/BZR1可直接调控数千个下游响应基因的表达。在模式植物拟南芥中的研究表明,BR的生物合成和信号转导通路成员,特别是BIN2和其下游的转录因子BES1/BZR1,可以被各种环境因子广泛地调节。本文系统总结了BR相关的最新研究进展,对BR的生物合成和信号转导是如何被复杂的环境因子所调节,以及BR与环境因子如何协同调控作物重要农艺性状、冷胁迫和盐胁迫的响应进行了综述。     

Role of Lipase from Community-Associated Methicillin-Resistant Staphylococcus aureus Strain USA300 in Hydrolyzing Triglycerides into Growth-Inhibitory Free Fatty Acids

Part of the human host innate immune response involves the secretion of bactericidal lipids on the skin and delivery of triglycerides into abscesses to control invading pathogens. Two Staphylococcus aureus lipases, named SAL1 and SAL2, were identified in the community-associated methicillin-resistant S. aureus strain USA300, which, presumably, are produced and function to degrade triglycerides to release free fatty acids. We show that the SAL2 lipase is one of the most abundant proteins secreted by USA300 and is proteolytically processed from the 72-kDa proSAL2 to the 44-kDa mature SAL2 by the metalloprotease aureolysin. We show that spent culture supernatants had lipase activity on both short- and long-chain fatty acid substrates and that deletion of gehB, encoding SAL2, resulted in the complete loss of these activities. With the use of gas chromatography-mass spectrometry, we show that SAL2 hydrolyzed trilinolein to linoleic acid, a fatty acid with known antistaphylococcal properties. When added to cultures of USA300, trilinolein and, to a lesser extent, triolein inhibited growth in a SAL2-dependent manner. This effect was shown to be due to the enzymatic activity of SAL2 on these triglycerides, since the catalytically inactive SAL2 Ser412Ala mutant was incapable of hydrolyzing the triglycerides or yielding delayed growth in their presence. Overall, these results reveal that SAL2 hydrolyzes triglycerides of both short- and long-chain fatty acids and that the released free fatty acids have the potential to cause significant delays in growth, depending on the chemical nature of the free fatty acid.     

Interaction of free fatty acids and epinephrine in regulating hepatic glucose production in conscious dogs

To determine the effects of an increase in lipolysis on the glycogenolytic effect of epinephrine (EPI), the catecholamine was infused portally into 18-h-fasted conscious dogs maintained on a pancreatic clamp in the presence [portal (Po)-EPI+FFA, n = 6] and absence (Po-EPI+SAL, n = 6) of peripheral Intralipid infusion. Control groups with high glucose (70% increase) and free fatty acid (FFA; 200% increase; HG+FFA, n = 6) and high glucose alone (HG+SAL, n = 6) were also included. Hepatic sinusoidal EPI levels were elevated (Delta 568 +/- 77 and Delta 527 +/- 37 pg/ml, respectively) in Po-EPI+SAL and EPI+FFA but remained basal in HG+FFA and HG+SAL. Arterial plasma FFA increased from 613 +/- 73 to 1,633 +/- 101 and 746 +/- 112 to 1,898 +/- 237 micromol/l in Po-EPI+FFA and HG+FFA but did not change in EPI+SAL or HG+SAL. Net hepatic glycogenolysis increased from 1.5 +/- 0.3 to 3.1 +/- 0.4 mg x kg(-1) x min(-1) (P < 0.05) by 30 min in response to portal EPI but did not rise (1.8 +/- 0.2 to 2.1 +/- 0.3 mg x kg(-1) x min(-1)) in response to Po-EPI+FFA. Net hepatic glycogenolysis decreased from 1.7 +/- 0.2 to 0.9 +/- 0.2 and 1.6 +/- 0.2 to 0.7 +/- 0.2 mg x kg(-1) x min(-1) by 30 min in HG+FFA and HG+SAL. Hepatic gluconeogenic flux to glucose 6-phosphate increased from 0.6 +/- 0.1 to 1.2 +/- 0.1 mg x kg(-1) x min(-1) (P < 0.05; by 3 h) and 0.7 +/- 0.1 to 1.6 +/- 0.1 mg x kg(-1) x min(-1) (P < 0.05; at 90 min) in HG+FFA and Po-EPI+FFA. The gluconeogenic parameters remained unchanged in the Po-EPI+SAL and HG+SAL groups. In conclusion, increased FFA markedly changed the mechanism by which EPI stimulated hepatic glucose production, suggesting that its overall lipolytic effect may be important in determining its effect on the liver.