Gene Expression and Regulation of Higher Plants Under Soil Water Stress

Higher plants not only provide human beings renewable food, building materials and energy, but also play the most important role in keeping a stable environment on earth. Plants differ from animals in many aspects, but the important is that plants are more easily influenced by environment than animals. Plants have a series of fine mechanisms for responding to environmental changes, which has been established during their long-period evolution and artificial domestication. The machinery related to molecular biology is the most important basis. The elucidation of it will extremely and purposefully promote the sustainable utilization of plant resources and make the best use of its current potential under different scales. This molecular mechanism at least includes drought signal recognition (input), signal transduction (many cascade biochemical reactions are involved in this process), signal output, signal responses and phenotype realization, which is a multi-dimension network system and contains many levels of gene expression and regulation. We will focus on the physiological and molecular adaptive machinery of plants under soil water stress and draw a possible blueprint for it. Meanwhile, the issues and perspectives are also discussed. We conclude that biological measures is the basic solution to solving various types of issues in relation to sustainable development and the plant measures is the eventual way.Key Words: Higher plants, soil water stress, gene regulatory network, drought, anti-drought gene resources, signal, ion homeostasis, physiological mechanisms.     

胁迫条件下高等植物体内脯氨酸代谢及调节的研究进展

概述胁迫处理对Ｐｒｏ 代谢调节机理的研究近况，从分子水平上分析了胁迫下Ｐｒｏ 积累的原因，初步提出Ｐｒｏ 与多胺的相互关系     

Glutathione as an Antioxidant and Regulatory Molecule in Plants Under Abiotic Stress Conditions

The glutathione (GSH)/glutathione disulfide (GSSG) redox couple is involved in several physiologic processes in plants under both optimal and stress conditions. It participates in the maintenance of redox homeostasis in the cells. The redox state of the GSH/GSSG couple is defined by its reducing capacity and the half-cell reduction potential, and differs in the various organs, tissues, cells, and compartments, changing during the growth and development of the plants. When characterizing this redox couple, the synthesis, degradation, oxidation, and transport of GSH and its conjugation with the sulfhydryl groups of other compounds should be considered. Under optimal growth conditions, the high GSH/GSSG ratio results in a reducing environment in the cells which maintains the appropriate structure and activity of protein molecules because of the inhibition of the formation of intermolecular disulfide bridges. In response to abiotic stresses, the GSH/GSSG ratio decreases due to the oxidation of GSH during the detoxification of reactive oxygen species (ROS) and changes in its metabolism. The lower GSH/GSSG ratio activates various defense mechanisms through a redox signalling pathway, which includes several oxidants, antioxidants, and stress hormones. In addition, GSH may control gene expression and the activity of proteins through glutathionylation and thiol-disulfide conversion. This review discusses the size and redox state of the GSH pool, including their regulation, their role in redox signalling and defense processes, and the changes caused by abiotic stress.     

植物萜类次生代谢及其调控

植物次生代谢在植物生长发育、环境适应、抵御病虫害等方面发挥着重要作用,这些天然产物组成地球上最丰富的有机化合物的宝库．萜类是植物代谢产物中种类最多的一类,具有重要的生理和生态功能,一些成分还有应用价值．近十几年来,人们在萜类化合物的分离、鉴定、应用、生物合成、相关基因与基因族、酶蛋白结构和功能、代谢调控以及代谢工程等各方面取得了重大进展．本文概述了植物萜类化合物代谢及其调控领域的研究进展与发展趋势．     

Sucrose Metabolism in Bean Plants Under Water Deficit

The effects of water stress on sucrose metabolism were evaluatedin bean plants of Tacarigua variety grown for 25 d. Decreasingwater potential and relative water content were observed. Waterstress effects resulted in a decrease of sucrose phosphate synthase(SPS) in both total (substrate saturating conditions) and Pi-insensitive(substrate limiting conditions plus inorganic phosphate) activities.The SPS Pi-insensitive activity was lower than the total SPSactivity, but the decrease in activity induced by water deficitwas relatively lower in the Pi-insensitive; however the activationstate increased during the water deficit period. An increasein sucrose synthase activity increased the activities of bothneutral and acid invertases at moderate water stress (–0·8MPa) and decreased activities at severe water stress(–1·45 MPa). The activity values of neutral invertasewere lower than those for the acid invertase. The starch/sucroseratio decreased and the ratio of total glucose/total fructoseincreased. These results indicate a relevant physiological roleof SPS in bean plants under water stress. Key words: Acid invertase, sucrose phosphate synthase, sucrose synthase     

Linking Plants Functioning to Adaptive Responses Under Heat Stress Conditions: A Mechanistic Review

Journal of Plant Growth Regulation - The general circulation models estimated an average increase in global surface temperature about 4 °C (2.9 to 5.5 °C). Escalating...     

Calcium and Phosphate Regulation of Nitrogen Metabolism in the Cyanobacterium Spirulina platensis Under the High Light Stress

High light stress (40 W/m²)-induced alterations in the nitrogen assimilatory enzymes in Spirulina platensis were studied under the Ca²⁺ and phosphate (Pi)-supplemented as well as starved conditions. Results revealed that activities of nitrate reductase (NR), amino acid transferases (AST/GOT and ALT/GPT), and protease enzymes in the high-light-incubated cells were relatively higher under the Ca²⁺- and Pi-starved conditions. On the contrary, relative rates of glutamine synthetase (GS) and ATPase activities were lower in the Ca²⁺- and Pi-starved cells. But the Spirulina cells under the Ca²⁺- and Pi-added conditions showed enhanced activity of both GS and ATPase enzymes. During the high-light stress, a decline in the GS activity, particularly under the Ca²⁺- and Pi-starved conditions, was indicative of a nitrogen starvation-like condition. This could be one of the reasons for induction of the NR and protease enzymes. A higher rate of GS activity was recorded under both the Ca²⁺- and Pi-supplemented conditions, perhaps owing to the enhanced rate of ATPase activity in such conditions. But a declining pattern of both NR and protease activities in the presence of Ca²⁺ and Pi, despite the higher rate of ATPase activity, might involve some other mechanism like the protein-kinase system. Received: 11 May 2000 / Accepted: 13 June 2000     

Copper Nanoparticle Application Enhances Plant Growth and Grain Yield in Maize Under Drought Stress Conditions

Journal of Plant Growth Regulation - Abiotic stresses, including drought, detrimentally affect the growth and productivity of many economically important crop plants, leading to significant yield...     

植物干旱胁迫信号转导及其调控机制研究进展

干旱是严重限制作物生长及产量的环境因子之一。经过长期的进化,植物形成了一套响应干旱胁迫的信号转导机制,包括对干旱胁迫信号的感知,第二信使的产生,信号转导和信号网络的形成。信号转导的结果是导致相关基因的表达和蛋白的合成,进而引起植物体渗透调节及抗氧化系统的改变,最终使植物适应干旱逆境或增强植物抗旱能力。干旱胁迫通常会促进ROS的积累及其他次级信号分子的产生。MAPK级联途径是真核生物信号转导最为保守的途径,在植物的生长发育及各种胁迫信号的传导中均起着较重要的作用。综述干旱胁迫信号及ROS→MAPK和ROS→Ca2+介导的信号途径,以及信号转导途径的调控机制。     

Growth Control Under Stress: mTOR Regulation through the REDD1-TSC Pathway

Dysregulated signaling by the checkpoint kinase TOR (target of rapamycin) has been linked to numerous human cancers. The tuberous sclerosis tumor suppressors TSC1 and TSC2 form a protein complex that integrates and transmits cellular growth factor and stress signals to negatively regulate TOR activity. Several recent reports have identified the stress response gene REDD1 as an essential regulator of TOR activity through the TSC1/2 complex in both Drosophila and mammalian cells. REDD1 is induced in response both to hypoxia and energy stress, and cells that lack REDD1 exhibit highly defective TOR regulation in response to either of these stress signals. While the precise mechanism of REDD1 function remains to be determined, the finding that REDD1-dependent TOR regulation contributes to cell growth/cell size control in flies and mammals suggests that abnormalities of REDD1-mediated signaling might disrupt energy homeostasis and/or promote tumorigenesis.     

高等植物中异黄酮合成代谢及其调控

异黄酮是植物次级代谢过程中产生的酚类物质,豆科等植物中含量丰富,在动植物体内有着广泛的生理作用。本文综述了高等植物中异黄酮的合成代谢途径及其关键酶以及调控机理。     

Growth Cycle Metabolism of Plants in Relation to Flowering

An examination of the percentages of total carbohydrate, nitrogen (Kjeldahl) and ash has been made at various times in the growth cycle in six plants of varying growth habit. The time of formation of the flower initial in four species (fumitory, leek, radish and yellow water-lily) corresponds to a maximum in the curve showing percentage of total carbohydrate plus percentage of ash in the whole plant. The other two species (pea and bean) make their flower initials very early in the growth cycle, at a time when the amounts of carbohydrate plus ash are high because of the attachment of the plant to the large seed. These two species therefore also make their flower initials at a virtual maximum of carbohydrate plus ash. All six species of plants studied have mobile carbohydrate. The distribution of nutrients after flowering is discussed.     

Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress

Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radical emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.     

Inorganic Nitrogen Metabolism in Barley Roots Under Poorly Aerated Conditions

Nitrate reduction, nitrite reduction, and ammonium assimilationwere measured over c. 24 h in excised sterile barley roots,in air or under low oxygen tensions. Partial anoxia had relativelylittle effect, but the pathway of nitrogen assimilation wasseverely inhibited during complete anoxia, when the uptake ofnitrate ceased. Much of the nitrate which was present in theroots at the time of excision was apparently unavailable forassimilation. None of the reactions of the pathway served inplace of oxygen as an electron acceptor under anaerobic conditions.The concentration of nitrate in the external solution duringgrowth and during the experimental treatments had no directeffect on anaerobic ethanol formation, although an indirecteffect was noted which was due to variations in the carbohydratecontent of the tissue.     

植物抗坏血酸的合成和代谢以及相关酶基因的调控

本文对植物抗坏血酸的生物合成与代谢途径以及相关酶基因调控的研究进展作介绍。     

Regulation of Sucrose Metabolism in Higher Plants: Localization and Regulation of Activity of Key Enzymes

ABSTRACT

Sucrose (Sue) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Sue synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Sue degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.