Plant Anaerobic Stress as a Novel Trend in Ecological Physiology,Biochemistry, and Molecular Biology: 1. Establishment of a New Scientific Discipline

This review attempted to follow the establishment of a novel branch of biology arisen at the interfaces between plant physiology, biochemistry, and molecular biology—plant anaerobic stress. Most attention was given to the early period of these investigations, the activity of the members of International Society for Plant Anaerobiosis in particular, and the contribution of Russian scientists, who played a significant role at that time in the establishment and international recognition of this new trend. In this connection, the following points are considered: (1) Crawford's metabolic theory, which could not withstand experimental verification but induced an active discussion, thus stimulating further investigations in this field; (2) a concept of two main strategies of plant adaptation to anaerobic stress (true and apparent adaptation), which was put forward based on the following experimental data: (a) a discovery of a paradoxical phenomenon of hyper-sensitivity, but not hyper-resistance to anoxia, of the flood-tolerant plant roots (“apparent” tolerance); (b) the elucidation of the physiological role of oxygen transported from aerated organs of flood-tolerant plants to the roots inhabiting anaerobic environment; (c) demonstration of the key role of both energy metabolism, and (d) substrate providing for glycolysis and ethanolic fermentation in plants manifesting “true” tolerance to oxygen deprivation; (3) the discovery of plant stress proteins; and finally (4) pH-stat theory put forward by Davies.     

Biology and Biochemistry of Plant Phospholipases

Phospholipases are a complex group of enzymes that hydrolyze phospholipids. The plant phospholipase family is composed of multiple members with varying positional specificity, and each type is represented by multiple isoforms distinguishable by their structural, catalytic, and physiological characteristics. A large number of phospholipase genes and gene families have been identified and the biochemical properties of several members have been characterized, revealing considerable molecular and catalytic diversity. Forward and reverse genetics has further revealed that phospholipases are widely involved in physiological processes including lipid metabolism, cell signaling, and responses to biotic and abiotic stresses. Such studies have highlighted the potential biotechnological value of phospholipases as targets for improving stress tolerance. The catalytic diversity of various phospholipase isoforms is also of increasing interest for industrial biocatalysis. This review focuses on recently acquired information on biochemical, molecular and functional aspects of plant phospholipases.     

中国植物激素研究: 过去、现在和未来

为了迎接2006年10月在北京召开的“植物激素与绿色革命”香山会议, 使其更具影响力, 本刊组织了一期“植物激素专辑”。本文作为此专辑的序言, 对我国在该领域研究作了概述和评论, 以帮助读者全面地了解我国在该领域的研究历史、现状和未来发展趋势。本文回顾了中国植物激素研究在二十世纪八十年代之前的工作发展历程中的重要成果, 主要集中在生理学研究方面的成果。随着植物分子遗传学技术与原理的不断成熟以及我国经济的飞速发展, 特别是研究队伍的迅速成长, 我国科学家近年来在植物激素代谢调控、转运及激素信号转导等领域取得了重要进展, 特别是激素受体基因分离鉴定、激素控制株型以及激素间的相互作用等方面取得的突破性进展。基于国际植物激素总体研究前沿和我国优势领域, 我们展望提出了我国在植物激素研究领域的未来发展方向与趋势。     

Insights into the molecular dynamics of plant light-harvesting proteins in vivo

To understand physiological processes at the molecular level, new techniques are needed to determine the details of protein structure and dynamics in intact systems. We describe a specific example of such an approach, involving differential analysis of the carotenoid resonance Raman signal in the plant photosynthetic membrane. Carotenoids play important roles in the photosynthetic membrane and are particularly vital to photoprotective regulatory mechanisms. Our methodology selectively revealed the details of associations between specific carotenoid molecules and specific protein binding sites. Changes in the molecular configuration of these cofactors associated with alterations in the physiological state of the photosynthetic system were observed. This approach can be applied to a wide range of complex biological systems, whenever a protein with a light-absorbing cofactor is involved.     

DELLA 蛋白在植物生长发育中的作用

DELLA蛋白作为GA信号转导通路中起抑制作用的转录因子,是一类定位在核内的生长抑制蛋白,可以直接与植物体内关键转录因子的蛋白互作,进而在许多植物信号活动中发挥核心作用。该文对近年来国内外有关模式植物及果树、蔬菜、花卉、粮食作物等植物DELLA蛋白基因家族的鉴定、时空表达模式、蛋白结构、参与的GA信号转导机理、与光敏色素互作因子PIF及F box蛋白的互作及DELLA蛋白在植物种子萌发、形态建成、豆科植物根瘤菌共生、气孔关闭、植物抗逆反应等过程中的重要作用等方面的研究进展进行综述,并比较了DELLA蛋白基因家族在不同物种中的差异,对其今后的研究热点和方向进行了展望,为进一步探讨DELLA蛋白的功能提供信息。     

Digital Single-Cell Analysis of Plant Organ Development Using 3DCellAtlas

Diverse molecular networks underlying plant growth and development are rapidly being uncovered. Integrating these data into the spatial and temporal context of dynamic organ growth remains a technical challenge. We developed 3DCellAtlas, an integrative computational pipeline that semiautomatically identifies cell types and quantifies both 3D cellular anisotropy and reporter abundance at single-cell resolution across whole plant organs. Cell identification is no less than 97.8% accurate and does not require transgenic lineage markers or reference atlases. Cell positions within organs are defined using an internal indexing system generating cellular level organ atlases where data from multiple samples can be integrated. Using this approach, we quantified the organ-wide cell-type-specific 3D cellular anisotropy driving Arabidopsis thaliana hypocotyl elongation. The impact ethylene has on hypocotyl 3D cell anisotropy identified the preferential growth of endodermis in response to this hormone. The spatiotemporal dynamics of the endogenous DELLA protein RGA, expansin gene EXPA3, and cell expansion was quantified within distinct cell types of Arabidopsis roots. A significant regulatory relationship between RGA, EXPA3, and growth was present in the epidermis and endodermis. The use of single-cell analyses of plant development enables the dynamics of diverse regulatory networks to be integrated with 3D organ growth.     

Molecular Evolution of the Plant R Regulatory Gene Family

Anthocyanin pigmentation patterns in different plant species are controlled in part by members of the myc-like R regulatory gene family. We have examined the molecular evolution of this gene family in seven plant species. Three regions of the R protein show sequence conservation between monocot and dicot R genes. These regions encode the basic helix-loop-helix domain, as well as conserved N-terminal and C-terminal domains; mean replacement rates for these conserved regions are 1.02 X 10(-9) nonsynonymous nucleotide substitutions per site per year. More than one-half of the protein, however, is diverging rapidly, with nonsynonymous substitution rates of 4.08 X 10(-9) substitutions per site per year. Detailed analysis of R homologs within the grasses (Poaceae) confirm that these variable regions are indeed evolving faster than the flanking conserved domains. Both nucleotide substitutions and small insertion/deletions contribute to the diversification of the variable regions within these regulatory genes. These results demonstrate that large tracts of sequence in these regulatory loci are evolving at a fairly rapid rate.     

The Physiology, Genetics and Molecular Biology of Plant Aluminum Resistance and Toxicity

Aluminum (Al) toxicity is the primary factor limiting crop production on acidic soils (pH values of 5 or below), and because 50% of the world’s potentially arable lands are acidic, Al toxicity is a very important limitation to worldwide crop production. This review examines our current understanding of mechanisms of Al toxicity, as well as the physiological, genetic and molecular basis for Al resistance. Al resistance can be achieved by mechanisms that facilitate Al exclusion from the root apex (Al exclusion) and/or by mechanisms that confer the ability of plants to tolerate Al in the plant symplasm (Al tolerance). Compelling evidence has been presented in the literature for a resistance mechanism based on exclusion of Al due to Al-activated carboxylate release from the growing root tip. More recently, researchers have provided support for an additional Al-resistance mechanism involving internal detoxification of Al with carboxylate ligands (deprotonated organic acids) and the sequestration of the Al-carboxylate complexes in the vacuole. This is a field that is entering a phase of new discovery, as researchers are on the verge of identifying some of the genes that contribute to Al resistance in plants. The identification and characterization of Al resistance genes will not only greatly advance our understanding of Al-resistance mechanisms, but more importantly, will be the source of new molecular resources that researchers will use to develop improved crops better suited for cultivation on acid soils.     

The Physiology of Plant Integrity

The original concept of the plant integration system is presented and exemplified by the data from the studies of the regulatory controls that mediate the effects of red light (R) on the growth of etiolated maize seedlings. The integrity of higher-plant behavior depends on the functional activity and interaction of the dominant (control center). In vegetating plants as the simplest case, these centers include the shoot apex and the distal part of the root comprising the sensory tissues, the zones of the synthesis of specific hormones, and the zones of high morphogenetic and sink capacities. The system of propagating electric signals is usually devoid of the permanent generation centers. The dominant centers recognize the external and internal signals and induce the development of polarity (the bioelectric and physiological gradients), canalized connections (the conducting bundles), and oscillations. Trophic, hormonal, and electrophysiological signals of intercellular regulation are propagated along the conducting bundles and affect the intracellular membrane, metabolic, and genic control systems. The regulatory controls comprise the receptor cells recognizing the external and internal signals, the tissues of connection channels, the effector cells, and the feedback loop elements. When three-day-old etiolated maize (Zea maysL.) seedlings are treated with red light (RL), the photosignal is recognized by the phytochrome in the cells of the mesocotyl intercalary meristem; as a result, the positive biopotential is prolonged in these cells and in the coleoptilar node. An electric field (the receptor potential) thus produced would hamper, by electroosmosis, IAA transport from the coleoptile into the mesocotyl and in this way, would drastically inhibit the growth of the latter and temporarily promote the growth of the former. The primary leaves, also recognize R, as a result R promotes cell growth and the synthesis of gibberellins. The Ukhtomskii's principle of the dominant is used to interpret the plant ability for switching over its physiological systems in response to specific signals.     

GTP-Binding Regulatory Proteins in Higher Plant Cells

The exsitence of GTP-binding regulatory proteins (for short term, often refered as G-proteins) in higher plant cells is certain. G-proteins are classified into two groups based on their molecular structures, which are the heterotrimeric G-proteins (big G-proteins) that contain three different subunits and the small G-proteins that have only one subunit (monomeric G-proteins). All G-proteins are characterized by their properties to bind with and hydrolyze GTP, by which G-proteins function as transmembrane and intracellular signalling molecules. As a distinguished participant in signal transduction, G-proteins directly and/or indirectly regulate a number of physiological processes, such as regulation of phytochrome-related physiological processes and gene expression, involvement in blue-light response, K+-channel regulation, stomatal movement, hormone regulation, protein phosphrylation dephosphorylation, etc. Although G-proteins in plant cells have not been purified, the genes for a subunit of heterotrimeric G-proteins have been cloned. More evidences for the importance of G-proteins in plant signalling processes are rapidly accumulating.     

植物HY5蛋白结构与功能的研究进展

HY5（LONG HYPOCOTYL 5）为光形态建成的正调控因子,是光调控植物发育的分子开关。在光诱导的基因表达中,HY5调控着植物基因组中上千基因的表达,它既可以单独调控相关基因的表达,也可以与其他调控因子一起共同调控相关基因的表达。HY5蛋白除了在光形态建成中起作用外,还在植物激素的信号传递过程中起着极其重要的作用,它整合了光信号传递和植物激素的信号传递。本综述简要介绍HY5蛋白的结构、生理功能及其分子机制等方面有关的进展。     

Molecular Genetics and Developmental Physiology: Implications for Designing Better Forest Crops

Current tree biology related to tree genetics and breeding has two important developments that have not well been integrated in the literature. The first is the physiological and biochemical dissection of plant yield, whereas the second is the genetic mapping based on molecular markers, such as RFLPs, RAPDs, AFLPs, and microsatellites. Genetic mapping has revolutionized traditional quantitative genetic analysis by which the genetic variation of a character is described in terms of its mean and (co)variance without the knowledge of the underlying genes. By integrating physiological and developmental studies of yield traits, genetic mapping can provide a unique means for detecting key QTL that play important roles in affecting tree growth and metabolism. The incorporation of these QTL into commercial populations through gene transformation or marker-assisted selection will move current breeding programs strictly based on an empirism to an approach that is mechanistically oriented. In this review, we discuss how plant physiology and development are merged with genetic mapping to formulate the strategy of molecular breeding in which superior forest crops are selected at the gene level. It is anticipated that this novel breeding strategy can potentially provide major breakthroughs for tree breeding.     

Protein Kinases in Neutrophils: A Review

In chemotactic factor-stimulated neutrophils, rapid increases of intracellular levels of cyclic AMP, calcium, and diacylglycerol have been observed and may be linked to protein kinase activation. The study of the physiological role and regulation of protein kinases in the neutrophil and the identification of their substrates has provided valuable information on the molecular mechanism of neutrophil activation. The focus of this review is on those aspects of protein kinases that are relevant to neutrophil activation and on the substrate proteins for these protein kinases. The possible role of protein phosphorylation in neutrophil function is also discussed.     

白桦BpERF98基因的遗传转化及非生物胁迫应答反应

非生物胁迫严重影响植物的生长发育,植物通过内部的分子调控机制抵御这种伤害,其中转录因子发挥了至关重要的作用。从野生型白桦（Betula platyphylla）叶片克隆BpERF98基因,通过农杆菌介导法获得过表达BpERF98的转基因白桦植株。测量转基因白桦和野生型白桦在低温、冻害和盐胁迫下的生理指标并进行差异性分析。通过分析发现,在非生物胁迫下转基因白桦的丙二醛含量及相对电导率均低于野生型株系,且转基因株系SOD和POD活性的增长明显高于野生型株系。结果表明,过表达BpERF98基因可以提高白桦对非生物胁迫的抵御能力,这为研究白桦在非生物胁迫下形成的分子机制及白桦抗性分子育种提供了依据。     

Combined application of methods to taxonomic identification of Saccharomyces strains in fermenting botrytized grape must

AIMS: Although numerous physiological and molecular methods have been proposed for yeast taxonomy, the unambiguous separation of Saccharomyces sensu stricto species in natural samples is still an incompletely resolved issue. In this study the power of various methods was compared in the identification of strains isolated from fermenting botrytized grape musts. METHODS AND RESULTS: Conventional taxonomic and physiological tests and molecular methods developed for rapid identification were used. CONCLUSIONS: None of the methods tested was sufficiently powerful. However, the combination of electrophoretic karyotyping and the PCR-RFLP of MET2 with growth tests at 10 and 37 degrees C provided results sufficient for species identification of Saccharomyces wine strains which were not interspecific hybrids or recombinants. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed combination of molecular and physiological methods allows specific taxonomic identification and separation of Saccharomyces wine strains without extensive genetic and molecular analysis. The proposed combined approach can also identify hybrids and recombinants.     

A stage-specific preparation to study the Ca(2+)-triggered fusion steps of exocytosis: rationale and perspectives

Despite groundbreaking work to identify numerous proteins and to focus attention on molecular interactions, the mechanism of calcium-triggered membrane fusion remains unresolved. A major difficulty in such research has been the many overlapping and interacting membrane trafficking steps in the secretory pathway, including those of membrane retrieval. Identifying the specific role(s) of a given protein, beyond its general involvement in exocytosis, has therefore proven problematic. Furthermore, the power of time-resolved optical and electrophysiological assays can be best applied to testing the function of known proteins rather than to the identification of unknown, critical membrane components. The identification of essential membrane constituents requires combined biochemical (molecular) and functional (physiological) analyses. A fully functional, stage-specific physiological membrane preparation would be one direct approach to dissecting the calcium-triggered fusion steps of regulated exocytosis. Herein we review our use of specific minimal membrane preparations consisting of fully primed and docked secretory vesicles, or the isolated vesicles themselves, and characterize the late events of exocytosis, with an aim towards identification of essential molecular components. We have established a functional definition of the fusion complex and its activation by calcium, based on our kinetic analyses. Together with a variety of biochemical and alternate functional assays, we have tested whether the SNARE core complex that is present in our vesicle membranes satisfies the criteria of the functionally defined fusion complex. Rather than a direct fusogenic role, the SNARE complex may promote the calcium sensitivity of fusion, possibly by defining or delimiting a localized, focal membrane fusion site that ensures rapid and efficient exocytosis in vivo.     

Physiology and pathophysiology of nitric oxide in the nervous system,with special mention of the islands of Calleja and the circunventricular organs

Nitric oxide (NO) has been recognized as a key regulatory factor in many physiological processes, including central nervous system function, development, and phatophysiology. NO is produced by a class of enzymes known as NO synthases (NOS) and in normal adult animals only the neuronal isoform (nNOS) is detectable. During cortical development, nNOS was found at E14 in neuroblasts of the marginal zone and its expression raised to a zenith by P5, decreasing afterwards until reaching a steady level by P10. At that time, nNOS was found mainly in pyramidal neurons. Interestingly, the inducible isoform of the enzyme (iNOS) was also active from P3 to P7, but it disappeared almost completely by P20. The neurodegeneration observed during normal aging and following hypoxic accidents seems to be the result of cumulative free radical damage, and excessive production of NO may be at the basis of the cascade. After ischemic events we observed an elevation in the number of neurons expressing nNOS coincident with an elevation in Ca2+-dependent NOS activity for up to 120 min. After this period, nNOS activity began to decrease but it was substituted by a rapid increase in Ca2+-independent activity coincident with the histological appearance of previously undetectable iNOS-immunoreactive neurons. These increases in NO production were accompanied by specific patterns of protein nitration, a process that seems to result in loss of protein function. In particular, we observed a correlation between exposure to ischemia-reperfusion and nitration of cytochrome c. This process was coincident with the exit of the cytochrome from the mitochondria to the surrounding cytoplasm, an early event in neuronal apoptosis. Interestingly, most of the morphological and molecular changes associated with ischemic damage were prevented by treatment with inhibitors of NO production, indicating a clear path in the search for efficacious drugs in the battle against cerebrovascular accidents.     

Regulation of K+ channel activities in plants: from physiological to molecular aspects

Plant voltage-gated channels belonging to the Shaker family participate in sustained K+ transport processes at the cell and whole plant levels, such as K+ uptake from the soil solution, long-distance K+ transport in the xylem and phloem, and K+ fluxes in guard cells during stomatal movements. The attention here is focused on the regulation of these transport systems by protein-protein interactions. Clues to the identity of the regulatory mechanisms have been provided by electrophysiological approaches in planta or in heterologous systems, and through analogies with their animal counterparts. It has been shown that, like their animal homologues, plant voltage-gated channels can assemble as homo- or heterotetramers associating polypeptides encoded by different Shaker genes, and that they can bind auxiliary subunits homologous to those identified in mammals. Furthermore, several regulatory processes (involving, for example, protein kinases and phosphatases, G proteins, 14-3-3s, or syntaxins) might be common to plant and animal Shakers. However, the molecular identification of plant channel partners is still at its beginning. This paper reviews current knowledge on plant K+ channel regulation at the physiological and molecular levels, in the light of the corresponding knowledge in animal cells, and discusses perspectives for the deciphering of regulatory networks in the future.