Transgenic plants tolerant to abiotic stresses

The publications containing data on the generation and study of transgenic plants tolerant to various types of abiotic stresses were analyzed. Mechanisms of plant protection against stresses and genes encoding a wide spectrum of compounds that confer the ability to survive under stress conditions, which cause inhibition of development and are even lethal to control plants are also discussed.     

血红素氧合酶与动脉粥样硬化

血红素氧合酶(HO)通过降解血红素产生一氧化碳(CO)、胆绿素和铁离子。CO是继一氧化氮(NO)之后发现的另一种具有重要生理作用的气体分子,具有调节血管张力、抑制血管平滑肌细胞增殖、抑制血小板聚集等效应;胆绿素和铁蛋白具有抗氧化和细胞保护作用。具有可诱导性的HO-1在心血管疾病尤其是在动脉粥样硬化及血管成形术后再狭窄中有重要的病理生理意义。HO-1的调控可能成为动脉粥样硬化防治的新手段。     

Cytokinin action in response to abiotic and biotic stresses in plants

The phytohormone cytokinin was originally discovered as a regulator of cell division. Later, it was described to be involved in regulating numerous processes in plant growth and development including meristem activity, tissue patterning, and organ size. More recently, diverse functions for cytokinin in the response to abiotic and biotic stresses have been reported. Cytokinin is required for the defence against high light stress and to protect plants from a novel type of abiotic stress caused by an altered photoperiod. Additionally, cytokinin has a role in the response to temperature, drought, osmotic, salt, and nutrient stress. Similarly, the full response to certain plant pathogens and herbivores requires a functional cytokinin signalling pathway. Conversely, different types of stress impact cytokinin homeostasis. The diverse functions of cytokinin in responses to stress and crosstalk with other hormones are described. Its emerging roles as a priming agent and as a regulator of growth‐defence trade‐offs are discussed.     

Heme oxygenase induction

The effect of repeated parenteral administration of aluminum (Al) was investigated to determine if a relationship exists between the severity of anemia and increase in hepatic heme oxygenase activity. Female Swiss Webster mice were dosed for 11 d with 50 mg Al/kg, as Al lactate, and sodium lactate was given to control mice. On d 12, hematocrit, hemoglobin, blood smears, hepatic heme oxygenase activity, and cytochrome P450 levels were assessed. Significant decreases in hematocrit (39.1±0.7 vs 43.1±0.3% in controls) and hemoglobin (13.1±0.4 vs 14.2±0.2 g/dL in controls) were produced by Al administration. Blood smears from Al-treated mice consistently showed smaller, more irregular red cells. Cytochrome P450 content was significantly decreased (0.443±0.043 vs 0.665±0.055 nmol/mg) whereas hepatic heme oxygenase activity was significantly increased (2.75±0.34 vs 1.66±0.20 nmol/mg/h) in Al-treated animals. The production of mild anemia by parenteral aluminum correlated significantly with the increase in heme oxygenase activity, which, although only 66% greater than in control, preceded a significant loss of cytochrome P450. The increased heme oxygenase activity, with subsequent increased destruction of heme and/or heme proteins is discussed as a possible mechanism for the microcytic, hypochromic anemia associated with Al overload.     

Brassinosteroids and their role in response of plants to abiotic stresses

Brassinosteroids (BRs) are polyhydroxylated steroidal plant hormones that play pivotal role in the regulation of various plant growth and development processes. BR biosynthetic or signaling mutants clearly indicate that these plant steroids are essential for regulating a variety of physiological processes including cellular expansion and proliferation, vascular differentiation, male fertility, timing senescence, and leaf development. Moreover, BRs regulate the expression of hundreds of genes, affect the activity of numerous metabolic pathways, and help to control overall developmental programs leading to morphogenesis. On the other hand, the potential application of BRs in agriculture to improve growth and yield under various stress conditions including drought, salinity, extreme temperatures, and heavy metal (Cd, Cu, Al, and Ni) toxicity, is of immense significance as these stresses severely hamper the normal metabolism of plants. Keeping in mind the multifaceted role of BRs, an attempt has been made to cover the various aspects mediated by BRs particularly under stress conditions and a possible mechanism of action of BRs has also been suggested.     

The roles of selenium in protecting plants against abiotic stresses

Selenium (Se), an essential element for animals and humans, has also been found to be beneficial to plants. In some countries around the world, such as China and Egypt, Se deficiency in the diet is a common problem. To counteract this problem, Se compounds have been used to increase the Se content in the edible parts of crops, through foliar sprays or base application of fertilizers. Se has also been shown to counteract various abiotic stresses induced in plants by cold, drought, high light, water, salinity and heavy metals (metalloids) (HMs), but the associated mechanisms are rather complicated and still remain to be fully elucidated. In this paper, we have focused on reviewing the effects of Se on HM-induced stress in plants, with an emphasis on the potential roles of Se compounds (e.g., selenite and selenate) in conferring tolerance against abiotic stresses. Numerous studies have implicated Se in the following mechanisms: the regulation of reactive oxygen species (ROS) and antioxidants, the inhibition of uptake and translocation of HM, changes in the speciation of HM and finally, rebuilding of the cell membrane and chloroplast structures and recovery of the photosynthetic system. In addition, two other mechanisms may be involved along with the established ones described above. Firstly, it may affect by regulating the uptake and redistribution of elements essential in the antioxidative systems or in maintaining the ion balance and structural integrity of the cell. Secondly, it may interfere with electron transport by affecting the assembly of the photosynthesis complexes. Future relevant studies should be increasingly focused on the changes in the cellular distribution of HM, the formation of Se–HM complexes, the substitution of S by the incorporation of Se into Se-Fe clusters and the relationships between Se, Fe, S and lipid peroxidation.     

Heme oxygenase and the kidney

Heme plays a significant pathogenic role in several diseases involving the kidney. The cellular content of heme, derived either from the delivery of filtered heme proteins such as hemoglobin and myoglobin, or from the breakdown of ubiquitous intracellular heme proteins, is regulated via the heme oxygenase enzyme system. Heme oxygenases catalyze the rate-limiting step in heme degradation, resulting in the formation of iron, carbon monoxide, and biliverdin, which is subsequently converted to bilirubin by biliverdin reductase. Recent attention has focused on the biological effects of product(s) of this enzymatic reaction, which have important antioxidant, anti-inflammatory, and cytoprotective functions. Three isoforms of heme oxygenase (HO) enzyme have been described: an inducible isoform, HO-1, and two constitutively expressed isoforms, HO-2 and HO-3. Induction of HO-1 occurs as an adaptive and beneficial response to several injurious stimuli, and has been implicated in many clinically relevant disease states including atherosclerosis, transplant rejection, endotoxic shock, hypertension, acute lung injury, acute renal injury, as well as others. This review will focus predominantly on the role of HO-1 in the kidney.     

Heme oxygenase and heme degradation

The microsomal heme oxygenase system consists of heme oxygenase (HO) and NADPH-cytochrome P450 reductase, and plays a key role in the physiological catabolism of heme which yields biliverdin, carbon monoxide, and iron as the final products. Heme degradation proceeds essentially as a series of autocatalytic oxidation reactions involving heme bound to HO. Large amounts of HO proteins from human and rat can now be prepared in truncated soluble form, and the crystal structures of some HO proteins have been determined. These advances have greatly facilitated the understanding of the mechanisms of individual steps of the HO reaction. HO can be induced in animals by the administration of heme or several other substances; the induction is shown to involve Bach1, a translational repressor. The induced HO is assumed to have cytoprotective effects. An uninducible HO isozyme, HO-2, has been identified, so the authentic HO is now called HO-1. HOs are also widely distributed in invertebrates, higher plants, algae, and bacteria, and function in various ways according to the needs of individual species.     

Heme oxygenase and the cardiovascular-renal system

Heme oxygenase (HO) has been shown to be important for attenuating the overall production of reactive oxygen species (ROS) through its ability to degrade heme and to produce carbon monoxide (CO), biliverdin/bilirubin, and the release of free iron. Excess free heme catalyzes the formation of ROS, which may lead to endothelial cell (EC) dysfunction as seen in numerous pathological conditions including hypertension and diabetes, as well as ischemia/reperfusion injury. The upregulation of HO-1 can be achieved through the use of pharmaceutical agents, such as metalloporphyrins and some HMG-CoA reductase inhibitors. Among other agents, atrial natriretic peptide and donors of nitric oxide (NO) are important modulators of the heme-HO system, either through induction of HO-1 or the biological activity of its products. Gene therapy and gene transfer, including site- and organ-specific targeted gene transfer, have become powerful tools for studying the potential role of HO-1/HO-2 in the treatment of various cardiovascular diseases as well as diabetes. HO-1 induction by pharmacological agents or gene transfer of human HO-1 into endothelial cells (ECs) in vitro increases cell-cycle progression and attenuates Ang II, TNF-, and heme-mediated DNA damage; administration in vivo acts to correct blood pressure elevation following Ang II exposure. Moreover, site-specific delivery of HO-1 to renal structures in spontaneously hypertensive rats (SHR), specifically to the medullary thick ascending limb of the loop of Henle (mTALH), has been shown to normalize blood pressure and provide protection to the mTAL against oxidative injury. In other cardiovascular situations, delivery of human HO-1 to hyperglycemic rats significantly lowers superoxide (O(2)(-)) levels and prevents EC damage and sloughing of vascular EC into the circulation. In addition, administration of human HO-1 to rats in advance of ischemia/reperfusion injury considerably reduces tissue damage. The ability to upregulate HO-1 through pharmacological means or through the use of gene therapy may offer therapeutic strategies for cardiovascular disease in the future. This review discusses the implications of HO-1 delivery during the early stages of cardiovascular system injury or in early vascular pathology and suggests that pharmacological agents that regulate HO activity or HO-1 gene delivery itself may become powerful tools for preventing the onset or progression of certain cardiovascular pathologies.     

Microarray: gateway to unravel the mystery of abiotic stresses in plants

Environmental factors, such as drought, salinity, extreme temperature, ozone poisoning, metal toxicity etc., significantly affect crops. To study these factors and to design a possible remedy, biological experimental data concerning these crops requires the quantification of gene expression and comparative analyses at high throughput level. Development of microarrays is the platform to study the differential expression profiling of the targeted genes. This technology can be applied to gene expression studies, ranging from individual genes to whole genome level. It is now possible to perform the quantification of the differential expression of genes on a glass slide in a single experiment. This review documents recently published reports on the use of microarrays for the identification of genes in different plant species playing their role in different cellular networks under abiotic stresses. The regulation pattern of differentially-expressed genes, individually or in group form, may help us to study different pathways and functions at the cellular and molecular level. These studies can provide us with a lot of useful information to unravel the mystery of abiotic stresses in important crop plants.     

Inhibitors of proteolytic enzymes under abiotic stresses in plants (review)

Data on the role of proteolytic enzyme inhibitors in plant adaptation to various unfavorable environmental abiotic factors--water deficiency, salinization of soil, extreme temperatures, etc.--and also probable functions of proteinases inhibitors in natural plant senescense are considered.     

Heme oxygenase up-regulation under salt stress protects nitrogen metabolism in nodules of soybean plants

The behaviour of enzymes involved in nitrogen metabolism, as well as oxidative stress generation and heme oxygenase gene and protein expression and activity, were analysed in soybean (Glycine max L.) nodules exposed to 50, 100 and 200 mM NaCl concentrations. A significant increase in lipid peroxidation was found with 100 and 200 mM salt treatments. Moreover, superoxide dismutase, catalase and peroxidase activities were decreased under 100 and 200 mM salt. Nitrogenase activity and leghemeoglobin content were diminished and ammonium content increased only under 200 mM NaCl. At 100 mM NaCl, glutamine synthetase (GS) and NADH-glutamate dehydrogenase (GDH) activities were similar to controls, whereas a significant increase (64%) in NADH-glutamate synthase (GOGAT) activity was observed. GS activity did not change at 200 mM salt treatment, but GOGAT and GDH significantly decreased (40 and 50%, respectively). When gene and protein expression of GS and GOGAT were analysed, it was found that they were positively correlated with enzyme activities. In addition, heme oxygenase (HO) activity, protein synthesis and gene expression were significantly increased under 100 mM salt treatment. Our data demonstrated that the up-regulation of HO, as part of antioxidant defence system, could be protecting the soybean nodule nitrogen fixation and assimilation under saline stress conditions.     

Epigenetics, a mode for plants to respond to abiotic stresses

Epigenetics has been becoming a hot topic in recent years.It can be mechanisms that regulate gene expression without changing DNA base sequence.In plants epigenetic regulation has been implicated to be...     

Complex molecular mechanisms determine fitness of plants to biotic and abiotic stresses

The mode of growth and development of plants does not allow them to change their habitat upon stress imposition. Through the course of evolution, plants have acquired complex molecular pathways to deal with abiotic and biotic factors to ensure their survival. The changing climatic conditions have led to unprecedented weather patterns resulting in increased crop losses. Similarly, the spread of pathogens in an era of increasing international trade has resulted in introduction and adaptation of these pathogens to new areas and cause frequent epidemics. There is an increasing need to understand the molecular mechanisms underlying stress responses in plants and envision ways to develop new crop varieties with improved features.

     

Heme oxygenase 1 overexpression increases iron fluxes in caco-2 cells

Heme oxygenase-1 is a microsomal enzyme that, when induced by stress, protects the cells from oxidative injury. Heme oxygenase-1 participates in the cleavage of the heme ring producing biliverdin, CO and ferrous Fe. The released Fe becomes part of intracellular Fe pool and can be stored in ferritin or released by an iron exporter. The mechanism by which heme enters cells is not completely understood, although it had been suggested that it might be internalized by an endocytosis process. In this study, we expressed a full-length Heme oxygenase-1 cDNA in Caco-2 cells and measured intracellular iron content, heme-iron uptake and transport and immunolocalization of heme oxygenase-1 in these cells. We found that heme oxygenasc-1 expressing cells showed increased apical heme iron uptake and transepithelial transport when compared to control cells. These results suggested that heme oxygenase-1 mediates heme iron influx and efflux in intestinal cells.     

Heme oxygenase 1: a novel oncogene in multiple gynecological cancers

Heme oxygenase 1 (HO-1), also known as heat shock protein 32 (HSP32), is a stress-inducible enzyme. In the past, it was believed to participate in maintaining cell homeostasis, reducing oxidative stress damage and exerting anti-apoptotic effects. When exposed to noxious stimulation, the expression of HO-1 in the body will increase, antagonizing these oxidative stresses and protecting our bodies. Recently, many studies showed that HO-1 was also highly-expressed in multiple gynecological cancers (such as ovarian cancer, cervical cancer and endometrial cancer), suggesting that it should be closely related to cell proliferation, metastasis, immune regulation and angiogenesis as an oncogene. This review summarizes the different effects of HO-1 under normal and diseased conditions with a brief discussion of its implications on the diagnosis and treatment of gynecological cancers, aiming to provide a new clue for prevention and treatment of diseases.     

Avenues of the membrane transport system in adaptation of plants to abiotic stresses

Abstract

Abiotic stress imposed by many factors such as: extreme water regimes, adverse temperatures, salinity, and heavy metal contamination result in severe crop yield losses worldwide. Plants must be able to quickly respond to these stresses in order to adapt to their growing conditions and minimize metabolic losses. In this context, transporter proteins play a vital role in regulating stress response mechanisms by facilitating movement of a variety of molecules and ions across the plasma membrane in order to maintain fundamental cellular processes such as ion homeostasis, osmotic adjustment, signal transduction, and detoxification. Aquaporins play a crucial role in alleviating abiotic stress by transporting water and other small molecules to maintain cellular homeostasis. Similarly, other transporter families such as CDF, ZIP, ABC, NHX, HKT, SWEETs, TMTs, and ion channels also contribute to abiotic stress tolerance. Hormones and other signaling molecules are necessary to coordinate responses across different tissues and to precisely regulate molecular trafficking. The present review highlights the current understanding of how membrane transporters orchestrate stress responses in plants. It also provides insights about the importance of these sensing and adaptive mechanisms for ensuring improved sustainable crop production during unfavorable conditions. Finally, this review discusses future prospects for the use of computational tools in constructing signaling networks to improve our understanding of the behavior of transporters under abiotic stress.