Although there were reports suggesting the involvement of endogenous cAMP in plant defense signaling cascades, there is no direct evidence supporting this notion yet and the detailed mechanism is unclear. In the prese...Although there were reports suggesting the involvement of endogenous cAMP in plant defense signaling cascades, there is no direct evidence supporting this notion yet and the detailed mechanism is unclear. In the present study, we have used pathogenic fungi Verticillium dahliae and Arabidopsis plants as a model system of plant-microb interaction to demonstrate the function of endogenous cAMP in Arabidopsis defense responses. Both V. dahliae inoculation and Verticillium toxins injection induced typical “wilt” symptoms in Arabidopsis seedlings. When either 8-Br-AMP (a membrane permeable cAMP analogue) or salicylic acid (SA) was applied to Arabidopsis, the plants became resistant to V. dahliae toxins. However, addition of 8-Br-AMP did not increase the resistance of Arabidopsis transgenic plants deficient in SA to the toxins, suggesting that cAMP might act upstream of SA in plant defense signaling pathway. Indeed, 8-Br-cAMP and forskolin, an activator of adenylyl cyclase, significantly stimulated the endogenous SA level in plants, whereas DDA, an inhibitor of adenylyl cyclase dramatically reduced toxin-induced SA increase. Both the endog- enous cAMP and SA increased significantly in Arabidopsis seedlings treated with toxins. Furthermore, transcription level of pathogenesis-related protein 1 gene (PR1) was strongly induced by both 8-Br-cAMP and the toxin treatment. Taken together, our data demonstrate that endogenous cAMP is involved in plant defense responses against Verticillium- secreted toxins by regulating the production of the known signal SA in plant defense pathway.展开更多
Phosphorus is one of the macronutrients essential for plant growth and development. Many soils around the world are deficient in phosphate （Pi） which is the form of phosphorus that plants can absorb and utilize. To ...Phosphorus is one of the macronutrients essential for plant growth and development. Many soils around the world are deficient in phosphate （Pi） which is the form of phosphorus that plants can absorb and utilize. To cope with the stress of Pi starvation, plants have evolved many elaborate strategies to enhance the acquisition and utilization of Pi from the environment. These strategies include morphological, biochemical and physiological responses which ultimately enable plants to better survive under low Pi conditions. Though these adaptive responses have been well described because of their ecological and agricultural importance, our studies on the molecular mechanisms underlying these responses are still in their infancy. In the last decade, significant progresses have been made towards the identification of the molecular components which are involved in the control of plant responses to Pi starvation. In this article, we first provide an overview of some major responses of plants to Pi starvation, then summarize what we have known so far about the signaling components involved in these responses, as well as the roles of sugar and phytohormones.展开更多
Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation fact...Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation factor Tu, respectively. Here, Arabidopsis thaliana mutants with changed calcium elevation （cce） in response to fig22 treatment were isolated and characterized. Besides novel mutant alleles of the fig22 receptor, FLS2 （Flagellin-Sensitive 2）, and the receptor-associated kinase, BAK1 （Brassinosteroid receptor 1-Associated Kinase 1）, the new cce mutants can be categorized into two main groups--those with a reduced or an enhanced calcium elevation. Moreover, cce mutants from both groups show differ- ential phenotypes to different sets of MAMPs. Thus, these mutants will facilitate the discovery of novel components in early MAMP signaling and bridge the gaps in current knowledge of calcium signaling during plant-microbe interactions. Last but not least, the screening method is optimized for speed （covering 384 plants in 3 or 10 h） and can be adapted to genetically dissect any other stimuli that induce a change in calcium levels.展开更多
Phosphotidylinositol (PI) can be hydrolyzed into inositol 1,4,5_ trisphosphate/diacylglycerol (IP 3/DAG), the second signalling messengers which can be further phosphorylated by phospholipases to other signalling mole...Phosphotidylinositol (PI) can be hydrolyzed into inositol 1,4,5_ trisphosphate/diacylglycerol (IP 3/DAG), the second signalling messengers which can be further phosphorylated by phospholipases to other signalling molecules, and phosphatidic acid (PA) and lysophosphoglyceride (lysoPI) involved in many signalling cascades. It has been shown that PI signalling pathway and the involved enzymes are critical for plant development and response to environmental factors. Three classes of phospholipases, named PLA 2, PLC and PLD, were classified based on their cleavage sites, and the presence of variants of isoforms indicating their different functions in plant growth/development. The update information of phospholipases with focus on the interaction of plant hormone and environmental factors has been provided.展开更多
Oxidative burst is one of the earliest responses in plant resistance to pathogen attack. Studies indicate that the oxidative burst is composed of two phases. The first burst is weak and biologically nonspecific, where...Oxidative burst is one of the earliest responses in plant resistance to pathogen attack. Studies indicate that the oxidative burst is composed of two phases. The first burst is weak and biologically nonspecific, whereas the phase Ⅱ burst is massive and produced only as an incompatible interaction. The rapid transient production of active oxygen species plays an important role in plant defense strategy against diseases. It involves: 1) antimicrobial activity, 2) substrate for oxidative cross_linking of cell wall, 3) triggering factor of hypersensitive response, 4) mobile signal inducing local and systemic acquired resistance by itself or its derivatives, 5) induction of phytoalexin accumulation, and 6) regulation of gene transcription. Emerging data indicate that the oxidative burst initiates from the activation of NADPH oxidase system resembling that of animal phagocytes. The generation of active oxygen species by a pH_dependent peroxidase is also present in some plants. Further, there is a complete system in plants to regulate the accumulation and scavenging of active oxygen species to protect plants from secondary infection, and at the same time to avoid the oxidative stress.展开更多
基金supported by the National Science Foundation of China(Grant No.39930010)a NSFC Fund for Creative Research Groups(Grant No.30421002)to Wei Hua WU
文摘Although there were reports suggesting the involvement of endogenous cAMP in plant defense signaling cascades, there is no direct evidence supporting this notion yet and the detailed mechanism is unclear. In the present study, we have used pathogenic fungi Verticillium dahliae and Arabidopsis plants as a model system of plant-microb interaction to demonstrate the function of endogenous cAMP in Arabidopsis defense responses. Both V. dahliae inoculation and Verticillium toxins injection induced typical “wilt” symptoms in Arabidopsis seedlings. When either 8-Br-AMP (a membrane permeable cAMP analogue) or salicylic acid (SA) was applied to Arabidopsis, the plants became resistant to V. dahliae toxins. However, addition of 8-Br-AMP did not increase the resistance of Arabidopsis transgenic plants deficient in SA to the toxins, suggesting that cAMP might act upstream of SA in plant defense signaling pathway. Indeed, 8-Br-cAMP and forskolin, an activator of adenylyl cyclase, significantly stimulated the endogenous SA level in plants, whereas DDA, an inhibitor of adenylyl cyclase dramatically reduced toxin-induced SA increase. Both the endog- enous cAMP and SA increased significantly in Arabidopsis seedlings treated with toxins. Furthermore, transcription level of pathogenesis-related protein 1 gene (PR1) was strongly induced by both 8-Br-cAMP and the toxin treatment. Taken together, our data demonstrate that endogenous cAMP is involved in plant defense responses against Verticillium- secreted toxins by regulating the production of the known signal SA in plant defense pathway.
文摘Phosphorus is one of the macronutrients essential for plant growth and development. Many soils around the world are deficient in phosphate （Pi） which is the form of phosphorus that plants can absorb and utilize. To cope with the stress of Pi starvation, plants have evolved many elaborate strategies to enhance the acquisition and utilization of Pi from the environment. These strategies include morphological, biochemical and physiological responses which ultimately enable plants to better survive under low Pi conditions. Though these adaptive responses have been well described because of their ecological and agricultural importance, our studies on the molecular mechanisms underlying these responses are still in their infancy. In the last decade, significant progresses have been made towards the identification of the molecular components which are involved in the control of plant responses to Pi starvation. In this article, we first provide an overview of some major responses of plants to Pi starvation, then summarize what we have known so far about the signaling components involved in these responses, as well as the roles of sugar and phytohormones.
基金This work was supported by a Deutsche Forschungsgemeinschaft (DFG) grant，financed by the DFG grant，by the Swiss National Science Foundation grant
文摘Calcium acts as a second messenger for signaling to a variety of stimuli including MAMPs （Microbe-Associated Molecular Patterns）, such as fig22 and elf18 that are derived from bacterial flagellin and elongation factor Tu, respectively. Here, Arabidopsis thaliana mutants with changed calcium elevation （cce） in response to fig22 treatment were isolated and characterized. Besides novel mutant alleles of the fig22 receptor, FLS2 （Flagellin-Sensitive 2）, and the receptor-associated kinase, BAK1 （Brassinosteroid receptor 1-Associated Kinase 1）, the new cce mutants can be categorized into two main groups--those with a reduced or an enhanced calcium elevation. Moreover, cce mutants from both groups show differ- ential phenotypes to different sets of MAMPs. Thus, these mutants will facilitate the discovery of novel components in early MAMP signaling and bridge the gaps in current knowledge of calcium signaling during plant-microbe interactions. Last but not least, the screening method is optimized for speed （covering 384 plants in 3 or 10 h） and can be adapted to genetically dissect any other stimuli that induce a change in calcium levels.
文摘Phosphotidylinositol (PI) can be hydrolyzed into inositol 1,4,5_ trisphosphate/diacylglycerol (IP 3/DAG), the second signalling messengers which can be further phosphorylated by phospholipases to other signalling molecules, and phosphatidic acid (PA) and lysophosphoglyceride (lysoPI) involved in many signalling cascades. It has been shown that PI signalling pathway and the involved enzymes are critical for plant development and response to environmental factors. Three classes of phospholipases, named PLA 2, PLC and PLD, were classified based on their cleavage sites, and the presence of variants of isoforms indicating their different functions in plant growth/development. The update information of phospholipases with focus on the interaction of plant hormone and environmental factors has been provided.
文摘Oxidative burst is one of the earliest responses in plant resistance to pathogen attack. Studies indicate that the oxidative burst is composed of two phases. The first burst is weak and biologically nonspecific, whereas the phase Ⅱ burst is massive and produced only as an incompatible interaction. The rapid transient production of active oxygen species plays an important role in plant defense strategy against diseases. It involves: 1) antimicrobial activity, 2) substrate for oxidative cross_linking of cell wall, 3) triggering factor of hypersensitive response, 4) mobile signal inducing local and systemic acquired resistance by itself or its derivatives, 5) induction of phytoalexin accumulation, and 6) regulation of gene transcription. Emerging data indicate that the oxidative burst initiates from the activation of NADPH oxidase system resembling that of animal phagocytes. The generation of active oxygen species by a pH_dependent peroxidase is also present in some plants. Further, there is a complete system in plants to regulate the accumulation and scavenging of active oxygen species to protect plants from secondary infection, and at the same time to avoid the oxidative stress.
