Heat tolerance in plants: An overview

▪ Abstract Many plants increase in freezing tolerance upon exposure to low nonfreezing temperatures, a phenomenon known as cold acclimation. In this review, recent advances in determining the nature and function of genes with roles in freezing tolerance and the mechanisms involved in low temperature gene regulation and signal transduction are described. One of the important conclusions to emerge from these studies is that cold acclimation includes the expression of certain cold-induced genes that function to stabilize membranes against freeze-induced injury. In addition, a family of Arabidopsis transcription factors, the CBF/DREB1 proteins, have been identified that control the expression of a regulon of cold-induced genes that increase plant freezing tolerance. These results along with many of the others summarized here further our understanding of the basic mechanisms that plants have evolved to survive freezing temperatures. In addition, the findings have potential practical applications as freezing te...

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PLANT COLD ACCLIMATION: Freezing Tolerance Genes and Regulatory Mechanisms

Plant cold acclimation: Freezing tolerance genes and regulatory mechanisms

Cold, salinity and drought stresses: an overview.

MUCKE aims to mine a large volume of images, to structure them conceptually and to use this conceptual structuring in order to improve large-scale image retrieval. The last decade witnessed important progress concerning low-level image representations. However, there are a number problems which need to be solved in order to unleash the full potential of image mining in applications. The central problem with low-level representations is the mismatch between them and the human interpretation of image content. This problem can be instantiated, for instance, by the incapability of existing descriptors to capture spatial relationships between the concepts represented or by their incapability to convey an explanation of why two images are similar in a content-based image retrieval framework. We start by assessing existing local descriptors for image classification and by proposing to use co-occurrence matrices to better capture spatial relationships in images. The main focus in MUCKE is on cleaning large scale Web image corpora and on proposing image representations which are closer to the human interpretation of images. Consequently, we introduce methods which tackle these two problems and compare results to state of the art methods. Note: some aspects of this deliverable are withheld at this time as they are pending review. Please contact the authors for a preview.

http://ieeexplore.ieee.org/iel2/4524/12820/00592460.pdf

Image Processing

▪ Abstract Temperature stresses experienced by plants can be classified into three types: those occurring at (a) temperatures below freezing, (b) low temperatures above freezing, and (c) high temperatures. This review outlines how biological substances that are deeply related to these stresses, such as heat-shock proteins, glycinebetaine as a compatible solute, membrane lipids, etc., and also detoxifiers of active oxygen species, contribute to temperature stress tolerance in plants. Also presented here are the uses of genetic engineering techniques to improve the adaptability of plants to temperature stress by altering the levels and composition of these substances in the living organism. Finally, the future prospects for molecular breeding are discussed.

ACCLIMATIVE RESPONSE TO TEMPERATURE STRESS IN HIGHER PLANTS: Approaches of Gene Engineering for Temperature Tolerance

ACCLIMATIVE RESPONSE TO TEMPERATURE STRESS IN HIGHER PLANTS: Approaches of

The stomata on the undersides of leaves control the exchange of carbon dioxide and water between plants and the atmosphere. Stomatal pore aperture is regulated by transport of ions and metabolites across guard-cell membranes. Perhaps surprisingly, until now no plant plasma membrane anion channel subunits have been cloned — and the homologues of animal anion channels have been shown not to encode functional ion channels in plants. Now two groups working independently have identified a protein that is an essential component for S-type anion channel function and is required for stomatal closure in response to a variety of physiological and stress stimuli. Termed SLAC1, it is a distant homologue of fungal and bacterial dicarboxylate/malic acid transport proteins. One of two related studies that describe the identification of a protein which is an essential component for S-type anion channel function and is required for stomatal closure in response to a variety of physiological and stress stimuli including carbon dioxide and ozone. The continuing rise in atmospheric [CO2] is predicted to have diverse and dramatic effects on the productivity of agriculture, plant ecosystems and gas exchange1,2,3. Stomatal pores in the epidermis provide gates for the exchange of CO2 and water between plants and the atmosphere, processes vital to plant life4,5,6. Increased [CO2] has been shown to enhance anion channel activity7 proposed to mediate efflux of osmoregulatory anions (Cl– and malate2–) from guard cells during stomatal closure8,9. However, the genes encoding anion efflux channels in plant plasma membranes remain unknown. Here we report the isolation of an Arabidopsis gene, SLAC1 (SLOW ANION CHANNEL-ASSOCIATED 1, At1g12480), which mediates CO2 sensitivity in regulation of plant gas exchange. The SLAC1 protein is a distant homologue of bacterial and fungal C4-dicarboxylate transporters, and is localized specifically to the plasma membrane of guard cells. It belongs to a protein family that in Arabidopsis consists of four structurally related members that are common in their plasma membrane localization, but show distinct tissue-specific expression patterns. The loss-of-function mutation in SLAC1 was accompanied by an over-accumulation of the osmoregulatory anions in guard cell protoplasts. Guard-cell-specific expression of SLAC1 or its family members resulted in restoration of the wild-type stomatal responses, including CO2 sensitivity, and also in the dissipation of the over-accumulated anions. These results suggest that SLAC1-family proteins have an evolutionarily conserved function that is required for the maintenance of organic/inorganic anion homeostasis on the cellular level.

CO2 regulator SLAC1 and its homologues are essential for anion homeostasis in plant cells

Reactive oxygen species (ROS) produced by NADPH oxidase play critical roles in various cellular activities, including plant innate immunity response. In contrast with the large multiprotein NADPH oxidase complex of phagocytes, in plants, only the homologs of the catalytic subunit gp91phox and the cytosolic regulator small GTPase Rac are found. Plant homologs of the gp91phox subunit are known as Rboh (for respiratory burst oxidase homolog). Although numerous Rboh have been isolated in plants, the regulation of enzymatic activity remains unknown. All rboh genes identified to date possess a conserved N-terminal extension that contains two Ca2+ binding EF-hand motifs. Previously, we ascertained that a small GTPase Rac (Os Rac1) enhanced pathogen-associated molecular pattern–induced ROS production and resistance to pathogens in rice (Oryza sativa). In this study, using yeast two-hybrid assay, we found that interaction between Rac GTPases and the N-terminal extension is ubiquitous and that a substantial part of the N-terminal region of Rboh, including the two EF-hand motifs, is required for the interaction. The direct Rac–Rboh interaction was supported by further studies using in vitro pull-down assay, a nuclear magnetic resonance titration experiment, and in vivo fluorescence resonance energy transfer (FRET) microscopy. The FRET analysis also suggests that cytosolic Ca2+ concentration may regulate Rac–Rboh interaction in a dynamic manner. Furthermore, transient coexpression of Os Rac1 and rbohB enhanced ROS production in Nicotiana benthamiana, suggesting that direct Rac–Rboh interaction may activate NADPH oxidase activity in plants. Taken together, the results suggest that cytosolic Ca2+ concentration may modulate NADPH oxidase activity by regulating the interaction between Rac GTPase and Rboh.

Regulation of Rice NADPH Oxidase by Binding of Rac GTPase to Its N-Terminal Extension

The chloroplast membrane of higher plants contains an unusually high concentration of trienoic fatty acids Plants grown in colder temperatures have a higher content of trienoic fatty acids Transgenic tobacco plants in which the gene encoding chloroplast omega-3 fatty acid desaturase, which synthesizes trienoic fatty acids, was silenced contained a lower level of trienoic fatty acids than wild-type plants and were better able to acclimate to higher temperatures

https://science.sciencemag.org/content/sci/287/5452/476.full.pdf

Koh Iba

Papers

ACCLIMATIVE RESPONSE TO TEMPERATURE STRESS IN HIGHER PLANTS: Approaches of Gene Engineering for Temperature Tolerance

ACCLIMATIVE RESPONSE TO TEMPERATURE STRESS IN HIGHER PLANTS: Approaches of

CO2 regulator SLAC1 and its homologues are essential for anion homeostasis in plant cells

Regulation of Rice NADPH Oxidase by Binding of Rac GTPase to Its N-Terminal Extension

Trienoic Fatty Acids and Plant Tolerance of High Temperature