Showing papers in "Annual Review of Plant Biology in 2005"
TL;DR: Identification of ABA metabolic genes has revealed that multiple metabolic steps are differentially regulated to fine-tune the ABA level at both transcriptional and post-transcriptional levels.
Abstract: The level of abscisic acid (ABAabscisic acid) in any particular tissue in a plant is determined by the rate of biosynthesis and catabolism of the hormone. Therefore, identifying all the genes involved in the metabolism is essential for a complete understanding of how this hormone directs plant growth and development. To date, almost all the biosynthetic genes have been identified through the isolation of auxotrophic mutants. On the other hand, among several ABA catabolic pathways, current genomic approaches revealed that Arabidopsis CYP707A genes encode ABA 8′-hydroxylases, which catalyze the first committed step in the predominant ABA catabolic pathway. Identification of ABA metabolic genes has revealed that multiple metabolic steps are differentially regulated to fine-tune the ABA level at both transcriptional and post-transcriptional levels. Furthermore, recent ongoing studies have given new insights into the regulation and site of ABA metabolism in relation to its physiological roles.
1,890 citations
TL;DR: In this article, the authors discuss the diversity of CCMs, their evolutionary origins, and the role of the environment in CCM modulation, and a multitude of environmental factors can exert regulatory effects on the expression of the CCM components.
Abstract: The evolution of organisms capable of oxygenic photosynthesis paralleled a long-term reduction in atmospheric CO2 and the increase in O2. Consequently, the competition between O2 and CO2 for the active sites of RUBISCO became more and more restrictive to the rate of photosynthesis. In coping with this situation, many algae and some higher plants acquired mechanisms that use energy to increase the CO2 concentrations (CO2 concentrating mechanisms, CCMs) in the proximity of RUBISCO. A number of CCM variants are now found among the different groups of algae. Modulating the CCMs may be crucial in the energetic and nutritional budgets of a cell, and a multitude of environmental factors can exert regulatory effects on the expression of the CCM components. We discuss the diversity of CCMs, their evolutionary origins, and the role of the environment in CCM modulation.
1,232 citations
TL;DR: Using a variety of approaches, researchers have begun to unravel the exquisite control mechanisms exerted by cells specialized for CaOx formation that include the machinery for uptake and accumulation of Ca, oxalic acid biosynthetic pathways, and regulation of crystal growth.
Abstract: Calcium oxalate (CaOx) crystals are distributed among all taxonomic levels of photosynthetic organisms from small algae to angiosperms and giant gymnosperms. Accumulation of crystals by these organisms can be substantial. Major functions of CaOx crystal formation in plants include high-capacity calcium (Ca) regulation and protection against herbivory. Ultrastructural and developmental analyses have demonstrated that this biomineralization process is not a simple random physical-chemical precipitation of endogenously synthesized oxalic acid and environmentally derived Ca. Instead, crystals are formed in specific shapes and sizes. Genetic regulation of CaOx formation is indicated by constancy of crystal morphology within species, cell specialization, and the remarkable coordination of crystal growth and cell expansion. Using a variety of approaches, researchers have begun to unravel the exquisite control mechanisms exerted by cells specialized for CaOx formation that include the machinery for uptake and accumulation of Ca, oxalic acid biosynthetic pathways, and regulation of crystal growth.
993 citations
TL;DR: Research in areas currently under exploration promises to provide a fuller understanding of the role redox plays in cellular processes, and to further the application of this knowledge to technology and medicine.
Abstract: Initially discovered in the context of photosynthesis, regulation by change in the redox state of thiol groups (S-S 2SH) is now known to occur throughout biology. Several systems, each linking a hydrogen donor to an intermediary disulfide protein, act to effect changes that alter the activity of target proteins: the ferredoxin/thioredoxin system, comprised of reduced ferredoxin, a thioredoxin, and the enzyme, ferredoxin-thioredoxin reductase; the NADP/thioredoxin system, including NADPH, a thioredoxin, and NADP-thioredoxin reductase; and the glutathione/glutaredoxin system, composed of reduced glutathione and a glutaredoxin. A related disulfide protein, protein disulfide isomerase (PDI) acts in protein assembly. Regulation linked to plastoquinone and signaling induced by reactive oxygen species (ROS) and other agents are also being actively investigated. Progress made on these systems has linked redox to the regulation of an increasing number of processes not only in plants, but in other types of organisms as well. Research in areas currently under exploration promises to provide a fuller understanding of the role redox plays in cellular processes, and to further the application of this knowledge to technology and medicine.
856 citations
TL;DR: Recent advances in the understanding of three distinct SI mechanisms, each controlled by two separate determinant genes at the S-locus are discussed.
Abstract: Sexual reproduction in many flowering plants involves self-incompatibility (SIself-incompatibility), which is one of the most important systems to prevent inbreeding. In many species, the self-/nonself-recognition of SI is controlled by a single polymorphic locus, the S-locus. Molecular dissection of the S-locus revealed that SI represents not one system, but a collection of divergent mechanisms. Here, we discuss recent advances in the understanding of three distinct SI mechanisms, each controlled by two separate determinant genes at the S-locus. In the Brassicaceae, the determinant genes encode a pollen ligand and its stigmatic receptor kinase; their interaction induces incompatible signaling(s) within the stigma papilla cells. In the Solanaceae-type SI, the determinants are a ribonuclease and an F-box protein, suggesting the involvement of RNA and protein degradation in the system. In the Papaveraceae, the only identified female determinant induces a Ca2+-dependent signaling network that ultimately resu...
602 citations
TL;DR: In flowering plants, male reproductive development requires the formation of the stamen, including the differentiation of anther tissues, which develops into pollen grains, relying on both sporophytic and gametophytic gene functions.
Abstract: In flowering plants, male reproductive development requires the formation of the stamen, including the differentiation of anther tissues. Within the anther, male meiosis produces microspores, which further develop into pollen grains, relying on both sporophytic and gametophytic gene functions. The mature pollen is released when the anther dehisces, allowing pollination to occur. Molecular studies have identified a large number of genes that are expressed during stamen and pollen development. Genetic analyses have demonstrated the function of some of these genes in specifying stamen identity, regulating anther cell division and differentiation, controlling male meiosis, supporting pollen development, and promoting anther dehiscence. These genes encode a variety of proteins, including transcriptional regulators, signal transduction proteins, regulators of protein degradation, and enzymes for the biosynthesis of hormones. Although much has been learned in recent decades, much more awaits to be discovered and understood; the future of the study of plant male reproduction remains bright and exciting with the ever-growing tool kits and rapidly expanding information and resources for gene function studies.
573 citations
TL;DR: Transgenic legumes with changed metabolic pathways and seed composition provide suitable models to study pathway regulation and metabolic control and desirable improvements of seed quality and yield may be achieved.
Abstract: Legume seed development is characterized by progressive differentiation of organs and tissues resulting in developmental gradients. The whole process is prone to metabolic control, and distinct metabolite profiles specify the differentiation state. Whereas early embryo growth is mainly maternally controlled, the transition into maturation implies a switch to filial control. A signaling network involving sugars, ABA, and SnRK1 kinases governs maturation. Processes of maturation are activated by changing oxygen/energy levels and/or a changing nutrient state, which trigger responses at the level of transcription and protein phosphorylation. This way seed metabolism becomes adapted to altering conditions. In maturing cotyledons photoheterotrophic metabolism improves internal oxygen supply and biosynthetic fluxes and influences assimilate partitioning. Transgenic legumes with changed metabolic pathways and seed composition provide suitable models to study pathway regulation and metabolic control. At the same time, desirable improvements of seed quality and yield may be achieved.
496 citations
TL;DR: This review discusses recent progress in identifying plant-specific CaM-binding proteins and their roles in response to biotic and abiotic stresses and development.
Abstract: CalmodulinCaM is a ubiquitous Ca2+ sensor protein (16 to 18 kD) with no catalytic activity that can, upon binding Ca2+, activate target proteins involved in various cellular processes. The CaM prototype is comprised of two globular domains connected with a long flexible helix. Each globular domain contains a pair of intimately linked EF hands. One EF hand motif is composed of a specialized helix-loop-helix structure that binds one molecule of Ca2+. (CaMcalmodulin) is the most prominent Ca2+ transducer in eukaryotic cells, regulating the activity of numerous proteins with diverse cellular functions. Many features of CaM and its downstream targets are similar in plants and other eukaryotes. However, plants possess a unique set of CaM-related proteins, and several unique CaM target proteins. This review discusses recent progress in identifying plant-specific CaM-binding proteins and their roles in response to biotic and abiotic stresses and development. The review also addresses aspects emerging from recent ...
379 citations
TL;DR: New studies dissecting the molecular and biochemical action of TTSS effectors show that these proteins contribute to bacterial pathogenicity by interfering with plant defense signal transduction.
Abstract: Phytopathogenic bacteria use the type III secretion system (TTSS) to inject effector proteins into plant cells. This system is essential for bacteria to multiply in plant tissue and to promote the development of disease symptoms. Until recently, little was known about the function of TTSS effectors in bacterial-plant interactions. New studies dissecting the molecular and biochemical action of TTSS effectors show that these proteins contribute to bacterial pathogenicity by interfering with plant defense signal transduction. These investigations provide us with a fresh view of how bacteria manipulate plant physiology to colonize their hosts.
323 citations
TL;DR: This work has demonstrated that covalent modifications of histones in the chromatin of target loci are part of the molecular mechanism by which certain repressors are silenced during vernalization.
Abstract: Exposure to the prolonged cold of winter is an important environmental cue that favors flowering in the spring in many types of plants. The process by which exposure to cold promotes flowering is known as vernalization. In Arabidopsis and certain cereals, the block to flowering in plants that have not been vernalized is due to the expression of flowering repressors. The promotion of flowering is due to the cold-mediated suppression of these repressors. Recent work has demonstrated that covalent modifications of histones in the chromatin of target loci are part of the molecular mechanism by which certain repressors are silenced during vernalization.
244 citations
TL;DR: The availability of fully sequenced plant genomes, the progress in bioinformatics to predict membrane transporters localized in plastids, and the development of highly sensitive proteomics techniques open new avenues toward identifying additional, to date unknown, plastid envelope membrane transportters.
Abstract: Plastids are metabolically extraordinarily active and versatile organelles that are found in all plant cells with the exception of angiosperm pollen grains. Many of the plastid-localized biochemical pathways depend on precursors from the cytosol and, in turn, many cytosolic pathways depend on the supply of precursor molecules from the plastid stroma. Hence, a massive traffic of metabolites occurs across the permeability barrier between plastids and cytosol that is called the plastid envelope membrane. Many of the known plastid envelope solute transporters have been identified by biochemical purification and peptide sequencing. This approach is of limited use for less abundant proteins and for proteins of plastid subtypes that are difficult to isolate in preparative amounts. Hence, the majority of plastid envelope membrane transporters are not yet identified at the molecular level. The availability of fully sequenced plant genomes, the progress in bioinformatics to predict membrane transporters localized in plastids, and the development of highly sensitive proteomics techniques open new avenues toward identifying additional, to date unknown, plastid envelope membrane transporters.
TL;DR: This review focuses on membrane and cytoskeleton dynamics in cell plate formation and expansion during somatic cytokinesis in plants.
Abstract: Cytokinesis partitions the cytoplasm between two or more nuclei. In higher plants, cytokinesis is initiated by cytoskeleton-assisted targeted delivery of membrane vesicles to the plane of cell division, followed by local membrane fusion to generate tubulo-vesicular networks. This initial phase of cytokinesis is essentially the same in diverse modes of plant cytokinesis whereas the subsequent transformation of the tubulovesicular networks into the partitioning membrane may be different between systems. This review focuses on membrane and cytoskeleton dynamics in cell plate formation and expansion during somatic cytokinesis.
TL;DR: This work discusses plant orthologs of mammalian-trafficking proteins involved in endocytotic cycling and progress in identifying distinct endosomal populations marked by the small GTPases Ara6 and Ara7 as well as recently described examples of apparent cycling of plasma membrane proteins.
Abstract: Plasma membrane protein internalization and recycling mechanisms in plants share many features with other eukaryotic organisms. However, functional and structural differences at the cellular and organismal level mandate specialized mechanisms for uptake, sorting, trafficking, and recycling in plants. Recent evidence of plasma membrane cycling of members of the PIN auxin efflux facilitator family and the KAT1 inwardly rectifying potassium channel demonstrates that endocytotic cycling of some form occurs in plants. However, the mechanisms underlying protein internalization and the signals that stimulate endocytosis of proteins from the cell-environment interface are poorly understood. Here we summarize what is known of endocytotic cycling in animals and compare those mechanisms with what is known in plants. We discuss plant orthologs of mammalian-trafficking proteins involved in endocytotic cycling. The use of the styryl dye FM4-64 to define the course of endocytotic uptake and the fungal toxin brefeldin A ...
TL;DR: Many examples of these processes are now available for three important gene families involved in production of volatile metabolites: the small molecule O-methyltransferases, the acyl transferases, and the terpene synthases.
Abstract: The world is filled with flavors and scents, which are the result of volatile compounds produced and emitted by plants These specialized metabolitesA metabolite, usually a small molecule, which is not a building block of proteins, lipids, or sugars, but that plays another role in the organism Usually, but not always, its occurrence is restricted are the products of specific metabolic pathways The terpenoid, fatty acid, and phenylpropanoid pathways contribute greatly to production of volatile compounds Mechanisms that lead to evolution of volatile production in plants include gene duplication and divergence, convergent evolution, repeated evolutionThis occurs when a new and identical (or very similar) genetic function arises independently in the same gene family from two or more orthologous or paralogous genes that did not share the same function, and alteration of gene expression, caused by a number of factors, followed by change in enzyme specificity Many examples of these processes are now availa
TL;DR: A large number of factors and protein complexes are now known to be involved in regulating the dynamic states of chromatin structure, and their biological functions and molecular mechanisms are beginning to be revealed.
Abstract: During the development of a multicellular organism, cell differentiation involves activation and repression of transcription programs that must be stably maintained during subsequent cell divisions. Chromatin remodeling plays a crucial role in regulating chromatin states that conserve transcription programs and provide a mechanism for chromatin states to be maintained as cells proliferate, a process referred to as epigenetic inheritance. A large number of factors and protein complexes are now known to be involved in regulating the dynamic states of chromatin structure. Their biological functions and molecular mechanisms are beginning to be revealed.
TL;DR: This review focuses on the use of inteins in plants as a split-gene technique to reconstitute the activity of a transgene product with the goal of limiting the spread of transgenes from a genetically modified plant to a weedy relative.
Abstract: Protein splicing elements, termed inteins, have been discovered in all the domains of life. Basic research on inteins has led to a greater understanding of how they mediate the protein splicing process. Because inteins are natural protein engineering elements they have been harnessed for use in a number of applications, including protein purification, protein semisynthesis, and in vivo and in vitro protein modifications. This review focuses on the use of inteins in plants. A split-gene technique utilizes inteins to reconstitute the activity of a transgene product with the goal of limiting the spread of transgenes from a genetically modified plant to a weedy relative. Furthermore, merging the intein tag for protein purification with the large protein yields possible with plants has the potential to produce pharmaceutically important proteins. Finally, relevant techniques that may be used in plants in the future are discussed.
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