非生物胁迫下植物脱水素的研究进展

脱水素是LEA蛋白中的一类,广泛存在于植物的各个组织器官及植物胚胎发育后期.脱水素是植物在受低温、干旱和高盐等非生物逆境胁迫时合成的一类高亲水性保护蛋白,具有保护核酸、胞内蛋白和膜结构免受损害的功能.许多研究已经证实在非生物胁迫下,植物脱水素的表达与积累和植物抗逆性之间存在着紧密的联系.对脱水素的结构、亚细胞定位、基因表达模式及非生物胁迫下脱水素作用的最新研究成果进行了综述.     

脱水素研究进展

脱水素(dehydrin)是植物体内的一种LEA蛋白,能够在植物胚胎发育后期以及逆境下大量表达,广泛存在于植物界。它是具有高度热稳定性的亲水性蛋白,有三类非常保守的区域,即K,Y和S片段。依据这三类片段的组成情况,可将脱水素分为5个基本类别。脱水素可通过多种转运方式定位于植物细胞的不同部位,以行使其功能。其基因的表达存在依赖ABA和不依赖ABA两种途径,并且受到多种环境因素的影响,能稳定细胞膜和许多大分子的结构以避免脱水对细胞造成的伤害。近年来,脱水素的结构和组成、在细胞中的定位及转运、基因的表达与调控、功能与作用机理等方面的研究已取得了很大的进展。     

小麦类脱水素的表达、纯化及多克隆抗体的制备

脱水素在胚胎发育后期累积,外源脱落酸(ABA)、低温、干旱和其他一些环境条件下能诱导脱水素的产生,尽管植物在脱水条件下脱水素广泛存在于细胞中,但其生化功能仍不清楚.为研究小麦在不同时期脱水素基因的表达情况和生物学功能及抗体制备,以小麦幼芽为材料,经干旱胁迫处理后,提取总RNA,通过RT-PCR得到小麦类脱水素基因片段(WZY1-1),再连接至克隆载体PUCM-T,并成功构建重组表达质粒PET-32a( )-wzy1-1,将阳性重组质粒转化于受体菌BL21(DE3)感受态细胞中,经IPTG诱导表达,进行表达产物的聚丙烯酰胺凝胶电泳(SDS-PAGE)检测.结果表明,表达蛋白位于37ku处,小麦类脱水素基因获得高效表达.表达蛋白经Ni2 琼脂糖凝胶亲和层析和透析袋电洗脱法纯化后,对兔子进行免疫,制备的抗血清通过ELISA检测到较高的多克隆抗体效价.蛋白质印迹结果显示,利用纯化的蛋白质制备的兔抗血清可以很好地和所表达的蛋白质带特异性结合,且郑引1号小麦幼苗进行干旱处理,提取粗蛋白,SDS-PAGE,蛋白质印迹检测显示,在分子质量28ku处出现特异的蛋白质条带,这说明所制备的抗血清可以与小麦叶片所表达的dehydrin蛋白特异性结合,证明其具有良好的免疫原性.     

植物冷驯化的分子机理研究进展

植物冷驯化是一个非常复杂的过程,包括植物将感受到的低温信号转变成生化信号,以激活冷诱导基因的启动子,刺激特定的mRNA的转录,并在特定的组织中合成冷驯化蛋白.冷驯化蛋白通过增强膜脂流动性和阻止胞间冰晶形成等方式,以保护细胞免受低温伤害.冷驯化基因的表达以转录后调控为主,也有转录调控.某些冷诱导基因也可受ABA或其他环境胁迫(如高温、干旱、高盐、脱水等)诱导表达.     

植物耐冷性分子机理的研究进展

近年来对植物耐冷性分子机理的研究不断深入。主要体现在以下4个方面：植物的冷敏感性可以通过调节膜脂的不饱和脂肪酸水平得到调控,调节的途径是通过酰脂去饱和酶和甘油-3-磷酸酰基转移酶的作用;利用转基因技术在植物中超表达抗氧化酶基因,如编码SOD、APX、CAT和GR等的基因,可望提高耐冷性;植物低温逆境信号转导的研究表明,ABA不仅是重要的低温逆境信号,而且可调节冷害下基因的表达,Ca^2 是一个主要的第二信使,蛋白激酶途径也参与了植物冷害的信号转导;低温诱导的蛋白或酶类主要有脱水蛋白和热稳定蛋白。     

低温胁迫下草菇甘油‐3‐磷酸酰基转移酶基因表达变化的研究

以草菇低温敏感型V23菌株与耐低温型VH3菌株为试验材料,将二者菌丝体置于冰浴中进行不同时间的低温胁迫处理。首先提取RNA,反转录为cDNA,然后构建含有微管蛋白(tubulin,TUB)基因片段和甘油‐3‐磷酸酰基转移酶(glycerol‐3‐phosphate acyltransferase,GPAT)基因片段的质粒,最终对GPAT基因在低温胁迫不同处理时间下的表达进行定量。结果表明,耐低温型的VH3菌株,在低温处理2h时,GPAT基因相对表达量上升,4h,表达量下降,6h上升,之后逐渐下降。低温敏感型V23菌株,在低温处理2h时,表达量下降,4h,表达量上升,此后逐渐下降;除低温处理4h外,V23菌株的GPAT基因表达量始终低于VH3菌株,初步推测GPAT基因的高表达与草菇的耐低温能力相关。     

植物耐冷性分子机理的研究进展

近年来对植物耐冷性分子机理的研究不断深入。主要体现在以下4个方面：植物的冷敏感性可以通过调节膜脂的不饱和脂肪酸水平得到调控,调节的途径是通过酰脂去饱和酶和甘油-3-磷酸酰基转移酶的作用;利用转基因技术在植物中超表达抗氧化酶基因,如编码SOD、 APX、CAT和GR等的基因,可望提高耐冷性;植物低温逆境信号转导的研究表明,ABA不仅是重要的低温逆境信号,而且可调节冷害下基因的表达,Ca2+是一个主要的第二信使,蛋白激酶途径也参与了植物冷害的信号转导;低温诱导的蛋白或酶类主要有脱水蛋白和热稳定蛋白。     

低温诱导蛋白及其与植物的耐寒性研究进展

低温诱导蛋白是植物在温度逆境条件下诱导产生的一系列蛋白,以抗冻蛋白、脱水蛋白、热激蛋白和热稳定蛋白较多,而且低温诱导蛋白质一旦在体内形成,植物体就会尽快地适应外界环境,表现出较强的抗逆性.本文对几种主要的低温诱导蛋白——抗冻蛋白、脱水蛋白、热激蛋白和热稳定蛋白的特性及其与植物耐寒性的关系研究进行综述,以期为进一步阐明植物耐寒的分子机制以及提高植物耐寒力研究提供新的思路.     

沙冬青脱水素基因转化紫花苜蓿的耐寒性研究

以紫花苜蓿品种‘中苜2号’为野生型材料,采用农杆菌介导法将沙冬青脱水素基因(dehydrin,AmDHN)导入紫花苜蓿基因组中并获得转基因植株,通过PCR和Southern blot杂交鉴定转基因植株,利用RT-PCR和qRT-PCR检测转基因植株中AmDHN基因及低温胁迫相关基因的表达量,并测定低温胁迫下苜蓿叶片的脯氨酸(Pro)和丙二醛(MDA)含量,从分子水平和生理指标两个层面研究转基因植株的抗寒特性,为进一步获得抗寒性较强的转基因苜蓿新材料提供依据。结果显示:(1)AmDHN基因已整合在转基因苜蓿植株基因组中,而且在不同的转基因株系中AmDHN的表达量也各不相同。(2)低温(4℃)处理后转基因植株中冷胁迫相关基因CBF2、CBF3、ProDH和CAS17的表达量明显高于同期野生对照;CBF2、CBF3和CAS17表达量在冷处理5h后都显著增加并达到最大值,而ProDH表达量在冷处理7d时最高,它们的最高值分别是对照的2.5、4、1.6和3倍左右。(3)苜蓿叶片的Pro和MDA含量均随低温处理时间延长而逐渐增加,转AmDHN基因苜蓿叶片的Pro含量始终高于同期野生型植株,而其MDA含量却始终低于同期野生型植株,且两类植株间差异均在胁迫14d时达到显著水平。因此,推测转AmDHN基因苜蓿中积累的AmDHN蛋白可能对一些酶的活性及膜系统起冷冻保护作用,从而使得转AmDHN基因紫花苜蓿的植株抗寒性提高,同时AmDHN也可能通过调控与低温相关基因的表达间接调节植物的耐低温能力。     

植物抗寒及其基因表达研究进展

植物经过逐渐降低的温度从而提高抗寒能力 ,这个过程被人们称为低温驯化。植物低温驯化过程是一个复杂的生理、生化和能量代谢变化过程 ,这些变化主要包括膜系统的稳定性、可溶性蛋白的积累和小分子渗透物质 ,比如脯氨酸、糖等 ,这些变化中的一些是植物抗寒必需的 ,而另外一些变化不是必需的。主要对冷害和低温生理生化变化、低温诱导表达基因的功能和作用、低温驯化的调节机制及其信号转导方面进行了综述。通过差别筛选 c DNA文库的方法已经鉴定了许多低温诱导表达、进而提高植物抗寒能力的基因 ,其中有脱水素、COR基因和 CBF1转录因子等。低温信号的感受、转导和调节表达是低温驯化的关键环节 ,低温信号的转导过程与干旱胁迫之间具有一定的交叉 ,这为利用 ABA等来提高植物抗寒能力成为可能 ,相信不久的将来人们可以通过提高植物抗寒能力从而增加经济产量成为现实。     

Atypical metabolisms and biochemical cycles imposing the cancerous state on plant cells

The biological, morphological and biochemical characteristics which define plant cancer cells at the end of a neoplasic progression in the absence of pathogens and which distinguish them from tumorous cells are summarized. Such plant cancer cells have in common with animal cancer cells many metabolic disturbances. The present paper reviews the biochemical changes in nitrogen, carbon, sugar and heme metabolisms which contribute to polyamine (PAs) accumulation. It indicates how these changes are interconnected and even form between each other biochemical cycles which likely maintain these cells in their irreversible state. The role of these cycles in the maintenance of such cells under a probable permanent oxidative stress is debated.     

From binding proteins to hormone receptors?

Phytohormones exert in responsive plant cells specific biochemical and physiological effects. It is a widely held view that phytohormones are first recognized by specific receptors which initiate the transduction of the hormonal signal. While hormone receptors are well studied in many eukaryotes ranging from yeast to man, we are lacking a detailed understanding of phytohormone receptors. Phytohormone binding proteins have been suspected to provide candidates for such receptors. In this review recent progress towards molecular analysis of such proteins and their genes will be summarized.     

Exocytosis in plants

Exocytosis is the final event in the secretory pathway and requires the fusion of the secretory vesicle membrane with the plasma membrane. It results in the release to the outside of vesicle cargo from the cell interior and also the delivery of vesicle membrane and proteins to the plasma membrane. An electrophysiological assay that measures changes in membrane capacitance has recently been used to monitor exocytosis in plants. This complements information derived from earlier light and electron microscope studies, and allows both transient and irreversible fusion of single exocytotic vesicles to be followed with high resolution in protoplasts. It also provides a tool to investigate bulk exocytotic activity in single protoplasts under the influence of cytoplasmic modulators. This research highlights the role of intracellular Ca²⁺, GTP and pressure in the control of exocytosis in plants.In parallel to these functional studies, plant proteins with the potential to regulate exocytosis are being identified by molecular analysis. In this review we describe these electrophysiological and molecular advances, and emphasise the need for parallel biochemical work to provide a complete picture of the mechanisms controlling vesicle fusion at the plasma membrane of plant cells.     

Growth-phase-dependent gene expression profiling of poplar (Populus alba x Populus tremula var. glandulosa) suspension cells

Complex sequences of morphological and biochemical changes occur during the developmental course of a batch plant cell culture. However, little information is available about the changes in gene expression that could explain these changes, because of the difficulties involved in isolating specific cellular events or developmental phases in the overlapping phases of cell growth. In an attempt to obtain such information we have examined the global growth phase-dependent gene expression of poplar cells in suspension cultures by cDNA microarray analysis. Our results reveal that significant changes occur in the expression of genes with functions related to protein synthesis, cell cycling, hormonal responses and cell wall biosynthesis, as cultures progress from initiation to senescence, that are highly correlated with observed developmental and physiological changes in the cells. Genes encoding protein kinases, calmodulin and proteins involved in both ascorbate metabolism and water-limited stress responses also showed strong stage-specific expression patterns. Our report provides fundamental information on molecular mechanisms that control cellular changes throughout the developmental course of poplar cell cultures.     

Higher plant microtubule-associated proteins (MAPs): A survey

Summary— Microtubule-associated proteins (MAPs) are one of the factors which regulate the different properties of microtubules during cell cycle and differentiation. They have been characterized as proteins which promote tubulin assembly in a concentration-dependent manner and bind to the outer surface of the polymers in vitro. Most of our knowledge comes from studies of neural microtubule-associated proteins and recent results highlight their implication in neuronal morphogenesis. In contrast, until recently, few data are available about the proteins that associate with plant tubulins. This is due principally to the fact that plant microtubule-associated proteins cannot be purified by the standard procedures used for neural microtubule-associated proteins. First, we will describe methods which have been used to isolate these proteins in plant cells. We will then discuss the biochemical and immunological properties of the plant microtubule-associated proteins which have been isolated. From these results, putative functions can be proposed for these proteins n the particular plant cytoskeleton activities.     

Characterization of Arabidopsis NEET reveals an ancient role for NEET proteins in iron metabolism

The NEET family is a newly discovered group of proteins involved in a diverse array of biological processes, including autophagy, apoptosis, aging, diabetes, and reactive oxygen homeostasis. They form a novel structure, the NEET fold, in which two protomers intertwine to form a two-domain motif, a cap, and a unique redox-active labile 2Fe-2S cluster binding domain. To accelerate the functional study of NEET proteins, as well as to examine whether they have an evolutionarily conserved role, we identified and characterized a plant NEET protein. Here, we show that the Arabidopsis thaliana At5g51720 protein (At-NEET) displays biochemical, structural, and biophysical characteristics of a NEET protein. Phenotypic characterization of At-NEET revealed a key role for this protein in plant development, senescence, reactive oxygen homeostasis, and Fe metabolism. A role in Fe metabolism was further supported by biochemical and cell biology studies of At-NEET in plant and mammalian cells, as well as mutational analysis of its cluster binding domain. Our findings support the hypothesis that NEET proteins have an ancient role in cells associated with Fe metabolism.