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Book Molecular and Genetic Analysis of NIMI dependent and Independent Induced Defense Response Pathways in Arabidopsis Thaliana

Download or read book Molecular and Genetic Analysis of NIMI dependent and Independent Induced Defense Response Pathways in Arabidopsis Thaliana written by Han Suk Kim and published by . This book was released on 2002 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Molecular and Genetic Analysis of NIM1 dependent and Independent Induced Defense Response Pathways in Arabidopsis Thaliana

Download or read book Molecular and Genetic Analysis of NIM1 dependent and Independent Induced Defense Response Pathways in Arabidopsis Thaliana written by Han Suk Kim and published by . This book was released on 2002 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the genetic screen, I identified five s & barbelow;uppressors o & barbelow;f n & barbelow;im1-1 (son) mutants that displayed varying levels of resistance to P. parasitica. The most resistant suppressor mutant, son1, did not induce any known SAR-defense related gene. I chose son1 for further molecular and genetic characterizations. Map-based cloning of SON1 revealed that it encodes a novel protein with an F-box motif, which has been associated with the SCF ubiquitin ligase complex involved in the ubiquitin-proteosome pathway.

Book Analysis of the Roles of Salicyclic Acid and NIM1 NPR1 in Arabidopsis Thaliana Pathogen Defense

Download or read book Analysis of the Roles of Salicyclic Acid and NIM1 NPR1 in Arabidopsis Thaliana Pathogen Defense written by Gregory James Rairdan and published by . This book was released on 2002 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plants have highly regulated signal transduction networks that control a rapid and potent antagonistic response to pathogenic organisms. I sought to better define these defense networks with respect to two molecules known to be important in plant defense: salicylic acid (SA) and the NIM1/NPR1 protein. I have used the model crucifer, Arabidopsis thaliana, to further define the role that these molecules play in race-specific resistance to Peronospora parasitica, and Pseudomonas syringae, oomycetic and bacterial pathogens, respectively. Plant resistance (R) genes encode proteins that initiate rapid, local, race-specific resistance against pathogens expressing a cognate avirulence (avr) gene. In Arabidopsis, most known R proteins contain leucine-rich repeats and a nucleotide binding domain, in combination with either a coiled-coiled domain or a Toll-Interleukin-1-homologous domain at their amino terminus. I tested if SA and/or NIM1/NPR1 was necessary for these two types of R genes to confer resistance to P. parasitica or P. syringae. The R genes RPM1, RPS2, RPS4, and RPP8 all required SA, but not NIM1/NPR1 for effective resistance, while RPP5 required both. These experiments, in addition to previous data, showed that there are defense responses which operated independently of NIM1/NPR1 and SA. We attempted to define some of the proteins important to NIM1/NPR1 and SA-independent defense responses by identifying genes that are expressed in response to pathogens, in SA-depleted (NahG) or nim1/npr1 mutant plants. Using cDNA-AFLP, we identified genes that are induced in wild-type, nim1 and NahG (SA-depleted) plants, genes induced in wild-type and nim1 plants, but not NahG plants, and genes induced only in wild-type plants. We further analyzed the expression of these genes to define their regulatory requirements, and determine whether these requirements varied according to the stimulus. We chose one SA-dependent, NIM1/NPR1-independently regulated gene, NIR1, for further study. I generated transgenic Arabidopsis expressing NIR1 promoter::GUS reporter construct and studied spatial NIR1-promoter-regulated expression in wild-type and npr1-2 backgrounds. In an effort to understand the role played by NIR genes, a mutagenized population of NIR1p::GUS npr1-2 plants was screened to identify mutants that underexpressed NIR1, and possible other NIR genes. One mutant, nue1 (N & barbelow;IR1-u & barbelow;ndere & barbelow;xpresser) was identified and characterized.

Book Activation of Arabidopsis Thalianad Defense Response Pathways by Oligogalacturonides and Flagellin

Download or read book Activation of Arabidopsis Thalianad Defense Response Pathways by Oligogalacturonides and Flagellin written by Carine Denoux and published by . This book was released on 2009 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pathogen attacks are perceived in Arabidopsis thaliana through recognition of pathogen- or microbe- associated molecular patterns (PAMPs/MAMPs). Although the study of various elicitors has revealed significant overlaps in defense response, the degrees of similarity/difference between MAMPs are not well defined. Oligogalacturonides (OGs), plant cell wall-derived elicitors, induce a wide range of defenses responses. Transcript profiling of Arabidopsis seedlings treated with OGs indicates that the response to OGs involves a transient response in the regulation of many genes. Among the genes, two cytochrome P450s, CYP81F2 and CYP82C3, are significantly induced shortly after OGs treatment. Monitoring the expression of these genes in a variety of defense-related mutants suggests that their rapid induction, mediated by OGs is independent of SA, JA, or Et signaling pathways. These reporter genes are also highly expressed in response to other MAMPs, including lipopolysaccharide (LPS), flagellin (Flg22), or chitin. Additional transcriptional analysis was carried out with OGs and pathogensynthesized flagellin (Flg22), two very different elicitors. Both triggered a fast and transient response that are similar. This response is characterized by activation of the early stages of multiple defense signaling pathways, particularly JA-associated processes. However, the response to Flg22 is stronger in the number of genes differentially expressed and the amplitude of change. The magnitude of genes induction was in both cases dose-dependent, but, even at very high concentrations, OGs did not induce as many genes as Flg22. Moreover, activation of senescence processes, SA-dependent secretory pathway genes, and PR1 expression was only observed with Flg22 elicitation. These results suggest a lower threshold for activation of early responses than for sustained late innate immune defenses. Induction of the Arabidopsis CYP81F2 gene is part of the early induced response to elicitors (OGs and Flg22). CYP81F2 gene expression is independent of the SA-, JAand Et-signaling pathways. CYP81F2 seems to catalyze the 4 methoxylation of indolic glucosinolates, which is required for callose formation in response to Flg22.

Book Plant Cellular Signaling in Response to Wounding Or Caterpillar Herbivory

Download or read book Plant Cellular Signaling in Response to Wounding Or Caterpillar Herbivory written by Jamuna Paudel and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Plants have complex signaling networks in response to wounding or caterpillar herbivory. The phytohormone jasmonic acid (JA) mediates the principal plant defense response pathway against caterpillar herbivory. However, some larval species manipulate host plant responses leading to the attenuation of this induced resistance (IR). Although the exact mechanism of the insect subversion of JA-mediated IR is not clearly understood, effectors in the labial salivary secretions of generalist Noctuid caterpillars, such as Spodoptera exigua, are known to activate the salicylic acid (SA)-mediated pathway that antagonize JA responses. Since the caterpillar labial saliva contains significant levels of oxido-reductive enzymes, such as glucose oxidase, it can manipulate cellular redox balance in plant tissues. Similarly, these effectors may activate the ethylene (ET) pathway leading to the modulation of JA pathway. The early cellular response to herbivory by 4th instar S. exigua caterpillars with intact and impaired labial saliva secretions was compared. Labial saliva helps maintain a reductive cellular environment in Arabidopsis thaliana leaves. Labial saliva-specific expression of the marker genes of the JA/ET- and SA-pathways was observed in A. thaliana and that was alleviated in glutathione-compromised pad2.1 or tga2/5/6 mutant plants. Also, caterpillar labial saliva modulated the expression of ET-dependent genes, ERF1 and AtHEL, in a glutathione-independent manner. Therefore, labial saliva of the caterpillar modulates the expression of defense-related genes in SA/NPR1-, glutathione-dependent or ET-, glutathione-independent manner. In comparison, cellular oxidative stress is elevated in the legume Medicago truncatula after caterpillar herbivory. The labial saliva-specific induction of the stress response is alleviated in the ET-insensitive skl mutant suggesting that ET is needed for this response. JA- and JA/ET- pathway marker genes are differentially expressed upon caterpillar herbivory in an ET-independent way. However, labial saliva-specific induction of the SA marker gene and suppression of trypsin inhibitor require ET perception suggesting that caterpillar labial saliva attenuates the JA-pathway by activating the SA pathway and ET modulates these responses. The role of caterpillar labial saliva in the plant defense signaling network was further explored by identifying differences in the post-translational modifications of nuclear proteins. Of the four proteins identified, the transcription factor, AtABF3, showed labial saliva-specific post-translational modification. In Arabidopsis plants subjected to herbivory by caterpillars with impaired labial saliva secretions, AtABF3 is nitrosylated at Cys420 and phosphorylated at Ser431. Since the expression of its downstream target gene, AtWRKY40, is also elevated in this plant, labial saliva-specific post-translational modification may play a role in the modulation of host defense response. As the levels of atmospheric carbon dioxide (CO2) are predicted to double in the next fifty years, the current scenario of plant stress response and, thus, the accumulation of defensive metabolites are expected to alter. Along with the increase of photosynthetic efficiency at elevated CO2, the plant's nitrogen use efficiency will be affected. Thus, plant responses to mechanical wounding at different levels of CO2 (ambient and elevated) and nitrogen fertilization (nitrate-limited and sufficient) were studied. At ambient CO2, mechanical wounding induced a jasmonates (JAs) burst and increased foliar glucosinolate (GSL) levels in Arabidopsis; however, at elevated CO2 conditions, this wound-responsive increase of JAs and GSLs are only observed under nitrate-stress conditions. Although MYB transcription factors that regulate both aliphatic or indole GSL biosynthesis are induced in response to wounding, a general shift from aliphatic GSL to indole GSL is observed in wounded Arabidopis leaves." --

Book Molecular Biological and Genetic Characterization of Synthetic Elicitor Activity in Arabidopsis Thaliana

Download or read book Molecular Biological and Genetic Characterization of Synthetic Elicitor Activity in Arabidopsis Thaliana written by Yasemin Bektas and published by . This book was released on 2015 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: DPMP is one of the strongest synthetic elicitors that were identified by our screening. It also exhibited hormesis effect at low doses and induces disease resistance at high doses. Its activity is fully dependent on NPR1 and partially dependent on WRKY70. Interestingly, two separate moieties of DPMP can independently induce immune responses. While their direct targets in plant defense are still yet to be defined, it is clear that they are powerful tools to dissect plant defense networks as well as develop novel pesticide alternatives

Book Genetic and Molecular Analysis of Disease Resistance in Arabidopsis Thaliana

Download or read book Genetic and Molecular Analysis of Disease Resistance in Arabidopsis Thaliana written by Karen Sue Century and published by . This book was released on 1996 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Arabidopsis Thaliana Class II TGA Transcription Factors are Essential Activators of Jasmonic Acid ethylene induced Defense Responses

Download or read book Arabidopsis Thaliana Class II TGA Transcription Factors are Essential Activators of Jasmonic Acid ethylene induced Defense Responses written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The three closely related Arabidopsis basic leucine zipper (bZIP) transcription factors TGA2, TGA5 and TGA6 are required for the establishment of the salicylic acid (SA)-dependent plant defense response systemic acquired resistance, which is effective against biotrophic pathogens. Here we show that the same transcription factors are essential for the activation of jasmonic acid (JA)- and ethylene (ET)-dependent defense mechanisms that counteract necrotrophic pathogens: the tga256 triple mutant is impaired in JA/ET-induced PDF1.2 and b-CHI expression, which correlates with a higher susceptibility against the necrotroph Botrytis cinerea. JA/ET induction of the trans-activators ERF1 and ORA59, which act upstream of PDF1.2, was slightly increased (ERF1) or unaffected (ORA59). PDF1.2 expression can be restored in the tga256 mutant by increased expression of ORA59, as observed in the tga256 jin1 quadruple mutant, which lacks the transcription factor JIN1/AtMYC2 that functions as a negative regulator of the JA/ET-dependent anti-fungal defense program. Whereas JA/ET-induced PDF1.2 expression is strongly suppressed by SA in wild-type plants, no negative effect of SA on PDF1.2 expression was observed in the tga256 jin1 quadruple mutant. These results imply that the antagonistic effects of TGA factors and JIN1/AtMYC2 on the JA/ET pathway are necessary to evoke the SA-mediated suppression of JA/ET-induced defense responses.

Book Genetic and Biochemical Analysis of Innate Immunity in Arabidopsis Thaliana

Download or read book Genetic and Biochemical Analysis of Innate Immunity in Arabidopsis Thaliana written by Cheng Cheng and published by . This book was released on 2014 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: Perception of evolutionarily conserved pathogen-associated molecular patterns (PAMPs) elicits rapid and profound transcriptional reprogramming in hosts and activates defense to pathogen attack. The molecular signaling networks underlying this plant pattern-triggered immunity (PTI) remain fragmented. We identified a series of mutants with altered pFRK1::LUC activity were identified and named as Arabidopsis genes governing immune gene expression (aggie) through forward genetic screening. Map-based cloning identified Aggie1 as encoding Arabidopsis C-terminal domain (CTD) phosphatase-like 3 (CPL3), a homolog of yeast FCP1 phosphatase that dephosphorylates the CTD of RNA polymerase II (RNAPII) during the transcription cycle. MAMP perception induced a rapid and transient CTD phosphorylation in Arabidopsis, underlying the modulation of CTD phosphorylation dynamics controlling plant immune responsive gene expression. Aggie1/CPL3 specifically dephosphorylated Ser2 of the CTD in vivo and in vitro and preferentially interacted with phosphorylated CTD. Transcriptional analysis indicates that cpl3 showed overall enhanced flg22-mediated transcription responses. Thus, Aggie1 negatively regulates immune responsive gene expression essential for suppression of pathogen growth by modulating the phosphorylation status of RNAPII CTD. Cyclin-dependent kinases C (CDKC) functions as RNAPII kinases. Interestingly, we also found the silencing of cdkc1 and cdkc2 in wild type reduced flg22-mediated transcription responses and the plants were more susceptible to Pseudomonas syringae DC3000, suggesting their positive role in PAMP-triggered immunity. Temperature fluctuation is a key determinant for microbial invasion into the host and for host evasion of the microbe. In contrast to mammals that maintain constant body temperature, plant internal temperature oscillates on a daily basis. It remains elusive how plants operate inducible defenses in response to temperature fluctuation. We report that ambient temperature changes lead to pronounced shifts of two distinct plant immune responses: pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI). Plants preferentially activate ETI signaling at relatively lower temperatures (10~23 ̊C), whereas they switch to PTI signaling at moderately elevated temperatures (23~32 ̊C). The Arabidopsis arp6 and hta9hta11 mutants, phenocopying plants grown at the elevated temperatures, exhibit enhanced PTI and yet reduced ETI responses. As the secretion of bacterial effectors favors low temperatures whereas bacteria multiply vigorously at elevated temperatures accompanied with increased MAMP production, our findings suggest that temperature oscillation might have driven dynamic co-evolution of distinct plant immune signaling responding to pathogen physiological changes. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151817

Book Identification and Characterization of Arabidopsis Toxicos En Levadura 12

Download or read book Identification and Characterization of Arabidopsis Toxicos En Levadura 12 written by Feng Kong and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plants have evolved complex systems to respond to changes in environmental conditions. Understanding the underlying signal transduction events in the plant response is crucial for greater insight into plant-environment interactions and to establish transgenic strategies to improve stress tolerance in crops. The aim of this dissertation was to identify and characterize the Arabidopsis Toxicos en Levadura 12 (ATL12) gene and explore the role of ATL12 in defense against powdery mildew and in salt stress tolerance. ATL12 encodes a conserved C3HC4 RING-type protein that has E3 ubiquitin ligase activity. Subcellular co-localization assays indicate that ATL12 localizes to the plasma membrane. Compared to Columbia wild-type, mutants in atl12 are more susceptible to fungal infection, whereas overexpression of ATL12 increased resistance to the fungus. Mutants of atl12 display a decreased seed germination rate, a reduction in root length growth, and a higher survival rate under high salt conditions. QRT-PCR studies showed that ATL12 is highly induced by chitin at early time points and its expression is linked to the activation of the MAPK cascade, pointing to the possible role of ATL12 in the early hypersensitive response and the local plant response to fungal pathogens. Additionally, the expression of respiratory burst oxidase homolog protein D/F was also found to decrease in the atl12 mutant, while the expression of ATL12 was not affected in atrbohd and atrbohf mutants. Together these data suggest that chitin-induced ATL12 expression is also linked to NADPH oxidase AtRBOHD/F-driven ROS production. ATL12 is also salt-inducible, and its expression is up-regulated at late stages in response to NaCl stress. Over-expression of ATL12 increases the expression of the salt stress-associated genes SOS1 and SOS2, and the ABA-dependent genes RD29B and RAB18. Further the expression of ATL12 was up-regulated after treatment with salicylic acid and jasmonic acid, indicating a possible role for ATL12 in plant hormone-mediated defense responses. In summary, these results indicate that ATL12 is involved in crosstalk between the SA-, JA-, chitin-induced MAPK, and NADPH oxidase-mediated defense responses against fungal pathogens and that it modulates salt stress responses through an ABA-dependent pathway and intensifying the ROS response in Arabidopsis thaliana.

Book Mechanisms and Consequences of Crosstalk Among Plant Defense Pathways Encoding Resistance to Pathogens and Herbivores

Download or read book Mechanisms and Consequences of Crosstalk Among Plant Defense Pathways Encoding Resistance to Pathogens and Herbivores written by Adam Kaveh Bahrami and published by . This book was released on 2007 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1 introduces the plant defense system from a historical perspective, focusing on the discovery of induced resistance and prior evidence for crosstalk among signaling pathways encoding resistance to pathogens and herbivores.