- Home
- A-Z Publications
- Annual Review of Plant Biology
- Previous Issues
- Volume 51, 2000
Annual Review of Plant Biology - Volume 51, 2000
Volume 51, 2000
- Review Articles
-
-
-
BIOTIN METABOLISM IN PLANTS
Vol. 51 (2000), pp. 17–47More Less▪ AbstractBiotin is an essential cofactor for a small number of enzymes involved mainly in the transfer of CO2 during HCO−3-dependent carboxylation reactions. This review highlights progress in plant biotin research by focusing on the four major areas of recent investigation: the structure, enzymology, and localization of two important biotinylated proteins (methylcrotonoyl-CoA carboxylase involved in the catabolism of leucine and noncyclic isoprenoids; acetyl-CoA carboxylase isoforms involved in a number of biosynthetic pathways); the biosynthesis of biotin; the biotinylation of biotin-dependent carboxylases, including the characterization of biotin holocarboxylase synthetase isoforms; and the detailed characterization of a novel, seed-specific biotinylated protein. A central challenge for plant biotin research is to determine in molecular terms how plant cells regulate the flow of biotin to sustain the biotinylation of biotin-dependent carboxylases during biosynthetic reactions.
-
-
-
SUGAR-INDUCED SIGNAL TRANSDUCTION IN PLANTS
Vol. 51 (2000), pp. 49–81More Less▪ AbstractSugars have important signaling functions throughout all stages of the plant's life cycle. This review presents our current understanding of the different mechanisms of sugar sensing and sugar-induced signal transduction, including the experimental approaches used. In plants separate sensing systems are present for hexose and sucrose. Hexokinase-dependent and -independent hexose sensing systems can further be distinguished. There has been progress in understanding the signal transduction cascade by analyzing the function of the SNF1 kinase complex and the regulatory PRL1 protein. The role of sugar signaling in seed development and in seed germination is discussed, especially with respect to the various mechanisms by which sugar signaling controls gene expression. Finally, recent literature on interacting signal transduction cascades is discussed, with particular emphasis on the ethylene and ABA signal transduction pathways.
-
-
-
THE CHLOROPLAST ATP SYNTHASE: A Rotary Enzyme?
Vol. 51 (2000), pp. 83–109More Less▪ AbstractThe chloroplast adenosine triphosphate (ATP) synthase is located in the thylakoid membrane and synthesizes ATP from adenosine diphosphate and inorganic phosphate at the expense of the electrochemical proton gradient formed by light-dependent electron flow. The structure, activities, and mechanism of the chloroplast ATP synthase are discussed. Emphasis is given to the inherent structural asymmetry of the ATP synthase and to the implication of this asymmetry to the mechanism of ATP synthesis and hydrolysis. A critical evaluation of the evidence in support of and against the notion that one part of the enzyme rotates with respect to other parts during catalytic turnover is presented. It is concluded that although rotation can occur, whether it is required for activity of the ATP synthase has not been established unequivocally.
-
-
-
NONPHOTOSYNTHETIC METABOLISM IN PLASTIDS
H. E. Neuhaus, and M. J. EmesVol. 51 (2000), pp. 111–140More Less▪ AbstractNonphotosynthetic plastids are important sites for the biosynthesis of starch, fatty acids, and the assimilation of nitrogen into amino acids in a wide range of plant tissues. Unlike chloroplasts, all the metabolites for these processes have to be imported, or generated by oxidative metabolism within the organelle. The aim of this review is to summarize our present understanding of the anabolic pathways involved, the requirement for import of precursors from the cytosol, the provision of energy for biosynthesis, and the interaction between pathways that share common intermediates. We emphasize the temporal and developmental regulation of events, and the variation in mechanisms employed by different species that produce the same end products.
-
-
-
PATHWAYS AND REGULATION OF SULFUR METABOLISM REVEALED THROUGH MOLECULAR AND GENETIC STUDIES
Vol. 51 (2000), pp. 141–165More Less▪ AbstractSulfur is essential for life. Its oxidation state is in constant flux as it circulates through the global sulfur cycle. Plants play a key role in the cycle since they are primary producers of organic sulfur compounds. They are able to couple photosynthesis to the reduction of sulfate, assimilation into cysteine, and further metabolism into methionine, glutathione, and many other compounds. The activity of the sulfur assimilation pathway responds dynamically to changes in sulfur supply and to environmental conditions that alter the need for reduced sulfur. Molecular genetic analysis has allowed many of the enzymes and regulatory mechanisms involved in the process to be defined. This review focuses on recent advances in the field of plant sulfur metabolism. It also emphasizes areas about which little is known, including transport and recycling/degradation of sulfur compounds.
-
-
-
(TRANS)GENE SILENCING IN PLANTS: How Many Mechanisms?
M. Fagard, and H. VaucheretVol. 51 (2000), pp. 167–194More Less▪ AbstractEpigenetic silencing of transgenes and endogenous genes can occur at the transcriptional level (TGS) or at the posttranscriptional level (PTGS). Because they can be induced by transgenes and viruses, TGS and PTGS probably reflect alternative (although not exclusive) responses to two important stress factors that the plant's genome has to face: the stable integration of additional DNA into chromosomes and the extrachromosomal replication of a viral genome. TGS, which results from the impairment of transcription initiation through methylation and/or chromatin condensation, could derive from the mechanisms by which transposed copies of mobile elements and T-DNA insertions are tamed. PTGS, which results from the degradation of mRNA when aberrant sense, antisense, or double-stranded forms of RNA are produced, could derive from the process of recovery by which cells eliminate pathogens (RNA viruses) or their undesirable products (RNA encoded by DNA viruses). Mechanisms involving DNA-DNA, DNA-RNA, or RNA-RNA interactions are discussed to explain the various pathways for triggering (trans)gene silencing in plants.
-
-
-
CEREAL CHROMOSOME STRUCTURE, EVOLUTION, AND PAIRING
Vol. 51 (2000), pp. 195–222More Less▪ AbstractThe determination of the order of genes along cereal chromosomes indicates that the cereals can be described as a single genetic system. Such a framework provides an opportunity to combine data generated from the studies on different cereals, enables chromosome evolution to be traced, and sheds light on key structures involved in cereal chromosome pairing. Centromeric and telomeric regions have been highlighted as important in these processes.
-
-
-
AGROBACTERIUMAND PLANT GENES INVOLVED IN T-DNA TRANSFER AND INTEGRATION
Vol. 51 (2000), pp. 223–256More Less▪ AbstractThe phytopathogenic bacterium Agrobacterium tumefaciens genetically transforms plants by transferring a portion of the resident Ti-plasmid, the T-DNA, to the plant. Accompanying the T-DNA into the plant cell is a number of virulence (Vir) proteins. These proteins may aid in T-DNA transfer, nuclear targeting, and integration into the plant genome. Other virulence proteins on the bacterial surface form a pilus through which the T-DNA and the transferred proteins may translocate. Although the roles of these virulence proteins within the bacterium are relatively well understood, less is known about their roles in the plant cell. In addition, the role of plant-encoded proteins in the transformation process is virtually unknown. In this article, I review what is currently known about the functions of virulence and plant proteins in several aspects of the Agrobacterium transformation process.
-
-
-
SIGNALING TO THE ACTIN CYTOSKELETON IN PLANTS
Vol. 51 (2000), pp. 257–288More Less▪ AbstractPlants have developed finely tuned, cellular mechanisms to respond to a variety of intrinsic and extrinsic stimuli. In several examples, these responses necessitate rearrangements of the cytoplasm that are coordinated by a network of actin microfilaments and microtubules, dynamic polymers collectively known as the cytoskeleton. This review focuses on five different cellular responses in which the actin cytoskeleton redistributes following extracellular stimulation: pollen tube tip growth and the self-incompatibility response; root hair responses to bacterial nodulation factors; light-mediated plastid positioning; nonhost resistance to fungal attack; and guard cell shape and turgor changes. For each of these systems, there is reasonable knowledge about what signals induce the plant response and the function(s) of the actin rearrangement. This review aims to build beyond a description of cytoskeletal changes and look at specific actin-binding proteins that have been implicated as effectors of each response, as sites of action for second messengers, and as fundamental coordinators of actin dynamics.
-
-
-
CYTOSKELETAL PERSPECTIVES ON ROOT GROWTH AND MORPHOGENESIS
Vol. 51 (2000), pp. 289–322More Less▪ AbstractGrowth and development of all plant cells and organs relies on a fully functional cytoskeleton comprised principally of microtubules and microfilaments. These two polymeric macromolecules, because of their location within the cell, confer structure upon, and convey information to, the peripheral regions of the cytoplasm where much of cellular growth is controlled and the formation of cellular identity takes place. Other ancillary molecules, such as motor proteins, are also important in assisting the cytoskeleton to participate in this front-line work of cellular development.
Roots provide not only a ready source of cells for fundamental analyses of the cytoskeleton, but the formative zone at their apices also provides a locale whereby experimental studies can be made of how the cytoskeleton permits cells to communicate between themselves and to cooperate with growth-regulating information supplied from the apoplasm.
-
-
-
THE GREAT ESCAPE: Phloem Transport and Unloading of Macromolecules1
Vol. 51 (2000), pp. 323–347More Less▪ AbstractThe phloem of higher plants translocates a diverse range of macromolecules including proteins, RNAs, and pathogens. This review considers the origin and destination of such macromolecules. A survey of the literature reveals that the majority of phloem-mobile macromolecules are synthesized within companion cells and enter the sieve elements through the branched plasmodesmata that connect these cells. Examples of systemic macromolecules that originate outside the companion cell are rare and are restricted to viral and subviral pathogens and putative RNA gene-silencing signals, all of which involve a relay system in which the macromolecule is amplified in each successive cell along the pathway to companion cells. Evidence is presented that xenobiotic macromolecules may enter the sieve element by a default pathway as they do not possess the necessary signals for retention in the sieve element–companion cell complex. Several sink tissues possess plasmodesmata with a high-molecular-size exclusion limit, potentially allowing the nonspecific escape of a wide range of small (<50-kDa) macromolecules from the phloem. Larger macromolecules and systemic mRNAs appear to require facilitated transport through sink plasmodesmata. The fate of phloem-mobile macromolecules is considered in relation to current models of long-distance signaling in plants.
-
-
-
DEVELOPMENT OF SYMMETRY IN PLANTS
Vol. 51 (2000), pp. 349–370More Less▪ AbstractPlant development involves specification and elaboration of axes of asymmetry. The apical-basal and inside-outside axes arise in embryogenesis, and are probably oriented maternally. They are maintained during growth post-germination and interact to establish novel axes of asymmetry in flowers and lateral organs (such as leaves). Whereas the genetic control of axis elaboration is now partially understood in embryos, floral meristems, and organs, the underlying mechanisms of axis specification remain largely obscure. Less functionally significant aspects of plant asymmetry (e.g. the handedness of spiral phyllotaxy) may originate in random events and therefore have no genetic control.
-
-
-
PLANT THIOREDOXIN SYSTEMS REVISITED
Vol. 51 (2000), pp. 371–400More Less▪ AbstractThioredoxins, the ubiquitous small proteins with a redox active disulfide bridge, are important regulatory elements in plant metabolism. Initially recognized as regulatory proteins in the reversible light activation of key photosynthetic enzymes, they have subsequently been found in the cytoplasm and in mitochondria. The various plant thioredoxins are different in structure and function. Depending on their intracellular location they are reduced enzymatically by an NADP-dependent or by a ferredoxin (light)-dependent reductase and transmit the regulatory signal to selected target enzymes through disulfide/dithiol interchange reactions. In this review we summarize recent developments that have provided new insights into the structures of several components and into the mechanism of action of the thioredoxin systems in plants.
-
-
-
SELENIUM IN HIGHER PLANTS
Vol. 51 (2000), pp. 401–432More Less▪ AbstractPlants vary considerably in their physiological response to selenium (Se). Some plant species growing on seleniferous soils are Se tolerant and accumulate very high concentrations of Se (Se accumulators), but most plants are Se nonaccumulators and are Se-sensitive. This review summarizes knowledge of the physiology and biochemistry of both types of plants, particularly with regard to Se uptake and transport, biochemical pathways of assimilation, volatilization and incorporation into proteins, and mechanisms of toxicity and tolerance. Molecular approaches are providing new insights into the role of sulfate transporters and sulfur assimilation enzymes in selenate uptake and metabolism, as well as the question of Se essentiality in plants. Recent advances in our understanding of the plant's ability to metabolize Se into volatile Se forms (phytovolatilization) are discussed, along with the application of phytoremediation for the cleanup of Se contaminated environments.
-
-
-
DIVERSITY AND REGULATION OF PLANT Ca2+ PUMPS: Insights from Expression in Yeast
Vol. 51 (2000), pp. 433–462More Less▪ AbstractThe spatial and temporal regulation of calcium concentration in plant cells depends on the coordinate activities of channels and active transporters located on different organelles and membranes. Several Ca2+ pumps have been identified and characterized by functional expression of plant genes in a yeast mutant (K616). This expression system has opened the way to a genetic and biochemical characterization of the regulatory and catalytic features of diverse Ca2+ pumps. Plant Ca2+-ATPases fall into two major types: AtECA1 represents one of four or more members of the type IIA (ER-type) Ca2+-ATPases in Arabidopsis, and AtACA2 is one of seven or more members of the type IIB (PM-type) Ca2+-ATPases that are regulated by a novel amino terminal domain. Type IIB pumps are widely distributed on membranes, including the PM (plasma membrane), vacuole, and ER (endoplasmic reticulum). The regulatory domain serves multiple functions, including autoinhibition, calmodulin binding, and sites for modification by phosphorylation. This domain, however, is considerably diverse among several type IIB ATPases, suggesting that the pumps are differentially regulated. Understanding of Ca2+ transporters at the molecular level is providing insights into their roles in signaling networks and in regulating fundamental processes of cell biology.
-
-
-
PLANT CELLULAR AND MOLECULAR RESPONSES TO HIGH SALINITY
Vol. 51 (2000), pp. 463–499More Less▪ AbstractPlant responses to salinity stress are reviewed with emphasis on molecular mechanisms of signal transduction and on the physiological consequences of altered gene expression that affect biochemical reactions downstream of stress sensing. We make extensive use of comparisons with model organisms, halophytic plants, and yeast, which provide a paradigm for many responses to salinity exhibited by stress-sensitive plants. Among biochemical responses, we emphasize osmolyte biosynthesis and function, water flux control, and membrane transport of ions for maintenance and re-establishment of homeostasis. The advances in understanding the effectiveness of stress responses, and distinctions between pathology and adaptive advantage, are increasingly based on transgenic plant and mutant analyses, in particular the analysis of Arabidopsis mutants defective in elements of stress signal transduction pathways. We summarize evidence for plant stress signaling systems, some of which have components analogous to those that regulate osmotic stress responses of yeast. There is evidence also of signaling cascades that are not known to exist in the unicellular eukaryote, some that presumably function in intercellular coordination or regulation of effector genes in a cell-/tissue-specific context required for tolerance of plants. A complex set of stress-responsive transcription factors is emerging. The imminent availability of genomic DNA sequences and global and cell-specific transcript expression data, combined with determinant identification based on gain- and loss-of-function molecular genetics, will provide the infrastructure for functional physiological dissection of salt tolerance determinants in an organismal context. Furthermore, protein interaction analysis and evaluation of allelism, additivity, and epistasis allow determination of ordered relationships between stress signaling components. Finally, genetic activation and suppression screens will lead inevitably to an understanding of the interrelationships of the multiple signaling systems that control stress-adaptive responses in plants.
-
-
-
GROWTH RETARDANTS: Effects on Gibberellin Biosynthesis and Other Metabolic Pathways
Vol. 51 (2000), pp. 501–531More Less▪ AbstractPlant growth retardants are applied in agronomic and horticultural crops to reduce unwanted longitudinal shoot growth without lowering plant productivity. Most growth retardants act by inhibiting gibberellin (GA) biosynthesis. To date, four different types of such inhibitors are known: (a) Onium compounds, such as chlormequat chloride, mepiquat chloride, chlorphonium, and AMO-1618, which block the cyclases copalyl-diphosphate synthase and ent-kaurene synthase involved in the early steps of GA metabolism. (b) Compounds with an N-containing heterocycle, e.g. ancymidol, flurprimidol, tetcyclacis, paclobutrazol, uniconazole-P, and inabenfide. These retardants block cytochrome P450-dependent monooxygenases, thereby inhibiting oxidation of ent-kaurene into ent-kaurenoic acid. (c) Structural mimics of 2-oxoglutaric acid, which is the co-substrate of dioxygenases that catalyze late steps of GA formation. Acylcyclohexanediones, e.g. prohexadione-Ca and trinexapac-ethyl and daminozide, block particularly 3ß-hydroxylation, thereby inhibiting the formation of highly active GAs from inactive precursors, and (d) 16,17-Dihydro-GA5 and related structures act most likely by mimicking the GA precursor substrate of the same dioxygenases. Enzymes, similar to the ones involved in GA biosynthesis, are also of importance in the formation of abscisic acid, ethylene, sterols, flavonoids, and other plant constituents. Changes in the levels of these compounds found after treatment with growth retardants can mostly be explained by side activities on such enzymes.
-
Previous Volumes
-
Volume 75 (2024)
-
Volume 74 (2023)
-
Volume 73 (2022)
-
Volume 72 (2021)
-
Volume 71 (2020)
-
Volume 70 (2019)
-
Volume 69 (2018)
-
Volume 68 (2017)
-
Volume 67 (2016)
-
Volume 66 (2015)
-
Volume 65 (2014)
-
Volume 64 (2013)
-
Volume 63 (2012)
-
Volume 62 (2011)
-
Volume 61 (2010)
-
Volume 60 (2009)
-
Volume 59 (2008)
-
Volume 58 (2007)
-
Volume 57 (2006)
-
Volume 56 (2005)
-
Volume 55 (2004)
-
Volume 54 (2003)
-
Volume 53 (2002)
-
Volume 52 (2001)
-
Volume 51 (2000)
-
Volume 50 (1999)
-
Volume 49 (1998)
-
Volume 48 (1997)
-
Volume 47 (1996)
-
Volume 46 (1995)
-
Volume 45 (1994)
-
Volume 44 (1993)
-
Volume 43 (1992)
-
Volume 42 (1991)
-
Volume 41 (1990)
-
Volume 40 (1989)
-
Volume 39 (1988)
-
Volume 38 (1987)
-
Volume 37 (1986)
-
Volume 36 (1985)
-
Volume 35 (1984)
-
Volume 34 (1983)
-
Volume 33 (1982)
-
Volume 32 (1981)
-
Volume 31 (1980)
-
Volume 30 (1979)
-
Volume 29 (1978)
-
Volume 28 (1977)
-
Volume 27 (1976)
-
Volume 26 (1975)
-
Volume 25 (1974)
-
Volume 24 (1973)
-
Volume 23 (1972)
-
Volume 22 (1971)
-
Volume 21 (1970)
-
Volume 20 (1969)
-
Volume 19 (1968)
-
Volume 18 (1967)
-
Volume 17 (1966)
-
Volume 16 (1965)
-
Volume 15 (1964)
-
Volume 14 (1963)
-
Volume 13 (1962)
-
Volume 12 (1961)
-
Volume 11 (1960)
-
Volume 10 (1959)
-
Volume 9 (1958)
-
Volume 8 (1957)
-
Volume 7 (1956)
-
Volume 6 (1955)
-
Volume 5 (1954)
-
Volume 4 (1953)
-
Volume 3 (1952)
-
Volume 2 (1951)
-
Volume 1 (1950)
-
Volume 0 (1932)