scholarly journals The bacterial type III-secreted protein AvrRps4 is a bipartite effector

2017 ◽  
Author(s):  
◽  
Morgan K. Halane
Keyword(s):  
Cell Death ◽  
Immune System ◽  
Resistance Genes ◽  
Pathogenic Bacteria ◽  
Global Climate ◽  
Plant Cells ◽  
Effector Proteins ◽  
Effector Domain ◽  
Cell Death Response ◽  
The Face

Like humans, plants have an immune system to protect themselves against invading pathogens. Unlike humans, however, the plant immune system is inborn and genetically predetermined by resistance genes. Pathogenic bacteria secrete proteins (effectors) into plant cells which manipulate the host cell, often to the benefit of the pathogen. The proteins encoded by resistance genes in resistant plants can specifically detect these effectors and ramp up a potent immune response, often resulting in cell death. By studying these effector proteins and how hosts can recognize them we hope to generate novel, durable methods to protect economically important plants from devastating pathogens. With a rapidly growing population in the face of global climate change it is more important than ever to protect the plants which we all use for food, fiber, and fuel. The effector AvrRps4 is recognized by the protein pair RPS4/RRS1. After delivery into plant cells AvrRps4 is processed into two parts (AvrRps4N and AvrRps4C). AvrRps4C was shown to trigger a cell death response in turnip and has been the most well-studied domain of AvrRps4. My research shows that AvrRps4N is also a functional effector domain. In some plants, in the absence of AvrRps4C, it enhances bacterial virulence. In resistant plants it enhances immunity in the presence of AvrRps4C. Finally, I show that AvrRps4N alone can trigger cell death on some plants, further confirming its role as a bona fide effector domain.

Cadmium‐mediated toxicity in plant cells is associated with the DCD / NRP ‐mediated cell death response

2021 ◽  
Author(s):  
Iana Pedro Silva Quadros ◽  
Nayara Nolasco Madeira ◽  
Virgílio Adriano Pereira Loriato ◽  
Thaina Fernanda Fillietaz Saia ◽  
Jéssica Coutinho Silva ◽  
...  
Keyword(s):  
Cell Death ◽  
Plant Cells ◽  
Cell Death Response

scholarly journals Identification and Functional Analysis of AopN, an Acidovorax Citrulli Effector that Induces Programmed Cell Death in Plants

2020 ◽  
Vol 21 (17) ◽  
pp. 6050 ◽  
Author(s):  
Xiaoxiao Zhang ◽  
Mei Zhao ◽  
Jie Jiang ◽  
Linlin Yang ◽  
Yuwen Yang ◽  
...  
Keyword(s):  
Functional Analysis ◽  
Cell Death ◽  
Programmed Cell Death ◽  
Pathogenic Bacteria ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Economic Losses ◽  
Homologous Protein ◽  
Acidovorax Citrulli ◽  
Effector Triggered Immunity

Bacterial fruit blotch (BFB), caused by Acidovorax citrulli, seriously affects watermelon and other cucurbit crops, resulting in significant economic losses. However, the pathogenicity mechanism of A. citrulli is not well understood. Plant pathogenic bacteria often suppress the plant immune response by secreting effector proteins. Thus, identifying A. citrulli effector proteins and determining their functions may improve our understanding of the underlying pathogenetic mechanisms. In this study, a novel effector, AopN, which is localized on the cell membrane of Nicotiana benthamiana, was identified. The functional analysis revealed that AopN significantly inhibited the flg22-induced reactive oxygen species burst. AopN induced a programmed cell death (PCD) response. Unlike its homologous protein, the ability of AopN to induce PCD was dependent on two motifs of unknown functions (including DUP4129 and Cpta_toxin), but was not dependent on LXXLL domain. More importantly, the virulence of the aopN mutant of A. citrulli in N. benthamiana significantly decreased, indicating that it was a core effector. Further analysis revealed that AopN interacted with watermelon ClHIPP and ClLTP, which responds to A. citrulli strain Aac5 infection at the transcription level. Collectively, these findings indicate that AopN suppresses plant immunity and activates the effector-triggered immunity pathway.

scholarly journals Ralstonia solanacearum Type III Effector RipAY Is a Glutathione-Degrading Enzyme That Is Activated by Plant Cytosolic Thioredoxins and Suppresses Plant Immunity

mBio ◽  
2016 ◽  
Vol 7 (2) ◽  
Author(s):  
Takafumi Mukaihara ◽  
Tadashi Hatanaka ◽  
Masahito Nakano ◽  
Kenji Oda
Keyword(s):  
Immune System ◽  
Ralstonia Solanacearum ◽  
Plant Immunity ◽  
Plant Cells ◽  
Effector Proteins ◽  
Yeast Cells ◽  
Yeast Growth ◽  
Type Iii Effector ◽  
Plant Immune System ◽  
Degradation Activity

ABSTRACT The plant pathogen Ralstonia solanacearum uses a large repertoire of type III effector proteins to succeed in infection. To clarify the function of effector proteins in host eukaryote cells, we expressed effectors in yeast cells and identified seven effector proteins that interfere with yeast growth. One of the effector proteins, RipAY, was found to share homology with the ChaC family proteins that function as γ-glutamyl cyclotransferases, which degrade glutathione (GSH), a tripeptide that plays important roles in the plant immune system. RipAY significantly inhibited yeast growth and simultaneously induced rapid GSH depletion when expressed in yeast cells. The in vitro GSH degradation activity of RipAY is specifically activated by eukaryotic factors in the yeast and plant extracts. Biochemical purification of the yeast protein identified that RipAY is activated by thioredoxin TRX2. On the other hand, RipAY was not activated by bacterial thioredoxins. Interestingly, RipAY was activated by plant h -type thioredoxins that exist in large amounts in the plant cytosol, but not by chloroplastic m -, f -, x -, y - and z -type thioredoxins, in a thiol-independent manner. The transient expression of RipAY decreased the GSH level in plant cells and affected the flg22-triggered production of reactive oxygen species (ROS) and expression of pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) marker genes in Nicotiana benthamiana leaves. These results indicate that RipAY is activated by host cytosolic thioredoxins and degrades GSH specifically in plant cells to suppress plant immunity. IMPORTANCE Ralstonia solanacearum is the causal agent of bacterial wilt disease of plants. This pathogen injects virulence effector proteins into host cells to suppress disease resistance responses of plants. In this article, we report a biochemical activity of R. solanacearum effector protein RipAY. RipAY can degrade GSH, a tripeptide that plays important roles in the plant immune system, with its γ-glutamyl cyclotransferase activity. The high GSH degradation activity of RipAY is considered to be a good weapon for this bacterium to suppress plant immunity. However, GSH also plays important roles in bacterial tolerance to various stresses and growth. Interestingly, RipAY has an excellent safety mechanism to prevent unwanted firing of its enzyme activity in bacterial cells because RipAY is specifically activated by host eukaryotic thioredoxins. This study also reveals a novel host plant protein acting as a molecular switch for effector activation.

scholarly journals The Potential Role of Lithium as an Antiviral Agent against SARS-CoV-2 via Membrane Depolarization: Review and Hypothesis

2021 ◽  
Vol 89 (1) ◽  
pp. 11
Author(s):  
Abdallah Barjas Qaswal ◽  
Aiman Suleiman ◽  
Hasan Guzu ◽  
Taima’a Harb ◽  
Bashir Atiyat
Keyword(s):  
Cell Death ◽  
Immune System ◽  
Antiviral Agent ◽  
Membrane Depolarization ◽  
The Body ◽  
Pyrin Domain ◽  
The Face ◽  
Preclinical And Clinical Studies ◽  
Receptor Family

Studies on potential treatments of Coronavirus Disease 2019 (COVID-19) are important to improve the global situation in the face of the pandemic. This review proposes lithium as a potential drug to treat COVID-19. Our hypothesis states that lithium can suppress NOD-like receptor family pyrin domain containing-3 (NLRP3) inflammasome activity, inhibit cell death, and exhibit immunomodulation via membrane depolarization. Our hypothesis was formulated after finding consistent correlations between these actions and membrane depolarization induced by lithium. Eventually, lithium could serve to mitigate the NLRP3-mediated cytokine storm, which is allegedly reported to be the inciting event of a series of retrogressive events associated with mortality from COVID-19. It could also inhibit cell death and modulate the immune system to attenuate its release, clear the virus from the body, and interrupt the cycle of immune-system dysregulation. Therefore, these effects are presumed to improve the morbidity and mortality of COVID-19 patients. As the numbers of COVID-19 cases and deaths continue to rise exponentially without a clear consensus on potential therapeutic agents, urgent conduction of preclinical and clinical studies to prove the efficacy and safety of lithium is reasonable.

scholarly journals Harpins, Multifunctional Proteins Secreted by Gram-Negative Plant-Pathogenic Bacteria

2013 ◽  
Vol 26 (10) ◽  
pp. 1115-1122 ◽  
Author(s):  
Min-Seon Choi ◽  
Wooki Kim ◽  
Chanhui Lee ◽  
Chang-Sik Oh
Keyword(s):  
Plant Growth ◽  
Pathogenic Bacteria ◽  
Plant Cells ◽  
Defense Responses ◽  
Effector Proteins ◽  
Gram Negative ◽  
Plant Pathogenic Bacteria ◽  
Heat Stable ◽  
Functional Aspects ◽  
A Cell

Harpins are glycine-rich and heat-stable proteins that are secreted through type III secretion system in gram-negative plant-pathogenic bacteria. Many studies show that these proteins are mostly targeted to the extracellular space of plant tissues, unlike bacterial effector proteins that act inside the plant cells. Over the two decades since the first harpin of pathogen origin, HrpN of Erwinia amylovora, was reported in 1992 as a cell-free elicitor of hypersensitive response (HR), diverse functional aspects of harpins have been determined. Some harpins were shown to have virulence activity, probably because of their involvement in the translocation of effector proteins into plant cytoplasm. Based on this function, harpins are now considered to be translocators. Their abilities of pore formation in the artificial membrane, binding to lipid components, and oligomerization are consistent with this idea. When harpins are applied to plants directly or expressed in plant cells, these proteins trigger diverse beneficial responses such as induction of defense responses against diverse pathogens and insects and enhancement of plant growth. Therefore, in this review, we will summarize the functions of harpins as virulence factors (or translocators) of bacterial pathogens, elicitors of HR and immune responses, and plant growth enhancers.

scholarly journals Identification of novel Ralstonia solanacearum type III effector proteins through translocation analysis of hrpB-regulated gene products

Microbiology ◽  
2009 ◽  
Vol 155 (7) ◽  
pp. 2235-2244 ◽  
Author(s):  
Takafumi Mukaihara ◽  
Naoyuki Tamura
Keyword(s):  
Ralstonia Solanacearum ◽  
Pathogenic Bacteria ◽  
Tandem Repeats ◽  
Plant Cells ◽  
Secretion System ◽  
Effector Proteins ◽  
Gene Products ◽  
Type Iii Effector ◽  
Type Iii ◽  
Effector Genes

The Hrp type III secretion system (TTSS) is essential for the pathogenicity of Ralstonia solanacearum on host plants. Hrp TTSS is a specialized secretion system that injects virulence proteins, the so-called type III effector proteins, into plant cells. In R. solanacearum, the expression of Hrp TTSS-related genes is regulated by an AraC-type transcriptional activator, HrpB. We have identified 30 hrpB-regulated hpx ( hrpB-dependent expression) genes and three well-known hrpB-regulated genes, popA, popB and popC, as candidate effector genes in R. solanacearum strain RS1000. In this study, we newly cloned 11 additional candidate effector genes that share homology with known hpx genes from R. solanacearum RS1000. Using a Cya reporter system, we investigated the translocation of these 44 gene products into plant cells via the Hrp TTSS and identified 34 effector proteins. These include three effector families composed of more than four members, namely the Hpx4, Hpx30 and GALA families. The Hpx30 family effectors are 2200–2500 aa in size and appear to be the largest class of effector proteins among animal- and plant-pathogenic bacteria. Members of this family contain 12–18 tandem repeats of a novel 42 aa motif, designated SKWP repeats.

scholarly journals Intra-strain elicitation and suppression of plant immunity by Ralstonia solanacearum type-III effectors in Nicotiana benthamiana

2019 ◽  
Author(s):  
Yuying Sang ◽  
Wenjia Yu ◽  
Haiyan Zhuang ◽  
Yali Wei ◽  
Lida Derevnina ◽  
...  
Keyword(s):  
Immune System ◽  
Immune Responses ◽  
Ralstonia Solanacearum ◽  
Plant Immunity ◽  
Plant Cells ◽  
Effector Proteins ◽  
Type Iii Effectors ◽  
Plant Immune System ◽  
Successful Infection ◽  
Genes Encoding

AbstractEffector proteins delivered inside plant cells are powerful weapons for bacterial pathogens, but this exposes the pathogen to potential recognition by the plant immune system. Therefore, the effector repertoire of a given pathogen must be balanced for a successful infection. Ralstonia solanacearum is an aggressive pathogen with a large repertoire of secreted effectors. One of these effectors, RipE1, is conserved in most R. solanacearum strains sequenced to date. In this work, we found that RipE1 triggers immunity in N. benthamiana, which requires the immune regulator SGT1, but not EDS1 or NRCs. Interestingly, RipE1-triggered immunity induces the accumulation of salicylic acid (SA) and the overexpression of several genes encoding phenylalanine-ammonia lyases (PALs), suggesting that the unconventional PAL-mediated pathway is responsible for the observed SA biosynthesis. Surprisingly, RipE1 recognition also induces the expression of jasmonic acid (JA)-responsive genes and JA biosynthesis, suggesting that both SA and JA may act cooperatively in response to RipE1. Finally, we found that RipE1 expression leads to the accumulation of glutathione in plant cells, which precedes the activation of immune responses. R. solanacearum encodes another effector, RipAY, which is known to inhibit immune responses by degrading cellular glutathione. Accordingly, we show that RipAY inhibits RipE1-triggered immune responses. This work shows a strategy employed by R. solanacearum to counteract the perception of its effector proteins by the plant immune system.

scholarly journals Lso-HPE1, an Effector of ‘Candidatus Liberibacter solanacearum’, Can Repress Plant Immune Response

2020 ◽  
Vol 110 (3) ◽  
pp. 648-655 ◽  
Author(s):  
Julien G. Levy ◽  
Rachel Gross ◽  
Azucena Mendoza-Herrera ◽  
Xiaotian Tang ◽  
Kevin Babilonia ◽  
...  
Keyword(s):  
Cell Death ◽  
Defense Mechanisms ◽  
Pathogenic Bacteria ◽  
Hypothetical Protein ◽  
Effector Proteins ◽  
Bactericera Cockerelli ◽  
Candidatus Liberibacter Solanacearum ◽  
Candidatus Liberibacter ◽  
Sec Translocon ◽  
Bacterial Effectors

‘Candidatus Liberibacter solanacearum’ is a plant pathogen affecting the families Solanaceae and Apiaceae in different parts of the world. ‘Ca. L. solanacearum’ is a Gram-negative, fastidious α-proteobacterium that is vectored by different psyllid species. Plant-pathogenic bacteria are known for interfering with the host physiology or defense mechanisms, often by secreting bacterial effectors. Effector proteins are critical for virulence; therefore, the identification of effectors could help with disease management. In this study, we characterized the Sec-translocon-dependent ‘Ca. L. solanacearum’–hypothetical protein effector 1 (Lso-HPE1). We compared this protein sequence in the different ‘Ca. L. solanacearum’ haplotypes. We predicted the signal peptide and validated its function using Escherichia coli’s alkaline phosphatase fusion assay. Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana demonstrated that Lso-HPE1 from ‘Ca. L. solanacearum’ haplotypes A and B were able to inhibit the induction of cell death in plants. We also compared gene expression of the Lso-HPE1- transcripts in ‘Ca. L. solanacearum’ haplotypes A and B in tomato and in the vector Bactericera cockerelli. This work validates the identification of a Sec-translocon-dependent ‘Ca. L. solanacearum’ protein possibly involved in suppression of plant cell death.

Immunomodulatory Effect of “Dr. M.S. Reddy’s Multiple Mixed Strain Probiotic Therapy” to Cure or Prevent Hospital Acquired (Nosocomial) Infections due to Clostridium difficile (C. diff), other Pathogenic Bacteria, and Autoimmune Diseases

2018 ◽  
Vol 11 (1) ◽  
pp. 3937-3949
Author(s):  
Malireddy S Reddy
Keyword(s):  
Immune System ◽  
Gastrointestinal Tract ◽  
Pathogenic Bacteria ◽  
Molecular Level ◽  
Host Immune System ◽  
Hospital Acquired Infections ◽  
The World ◽  
Probiotic Strains ◽  
The Individual ◽  
Hospital Acquired

The worldwide popularity of Dr. M.S. Reddy’s Multiple Mixed Strain Probiotic Therapy to treat or prevent the hospital acquired infections (nosocomial infections) arose a great interest in the medical community around the world (Reddy and Reddy, 2016; 2017). The following questions were raised on this subject: Does Multiple Mixed Strain Probiotics directly inhibit the pathogenic bacteria (C. diff) in the gastrointestinal tract or indirectly through modulation of the host immune system or both? To be more specific, what is the exact and/or hypothetical mechanism at molecular level behind the breakthrough discovery of Dr. M.S. Reddy’s Multiple Mixed Strain Probiotic Therapy?  To answer these questions, the specific immunomodulation regulatory functions of the individual Probiotic strains (on host) have beenresearched, investigated andoutlined in this article.  A detailed explanation(s) and hypotheses have been proposed outlining the possible cumulativedirect bacteriological and indirect immunomodulatory effects (at the molecular level) of the Multiple Mixed Strain Probiotics used in Dr. M.S. Reddy’s Multiple Mixed Strain Probiotic Therapy to successfully treat C. diff infection.  A detailed scientific and research attempts were made to correlate the Probiotic induced immune activities in relation to the reduction of the symptoms associated with the hospital acquired Clostridium difficile infection during and after the Multiple Mixed Strain Probioitc Therapy.  Results of the clinical trials, microbiological tests on feces, and the clinical blood tests significantly revealed that the reasons for the success of Dr. Reddy’s Multiple Mixed Strain Probiotic Therapy are multifold. Presumably, it is predominantly due to the immunomodulatory effect they have exerted on the host immune system along with the direct inhibition of C. diff bacteria by multiple Probiotics, due to the production of bacteriocins, lactic acid and nutritional competency.In addition, the size of the individual cells of the Probiotic strains in the Multiple Mixed Strain Probiotics and their significant effect on immunomodulation has been thoroughly discussed. Results clearly proved that if Probiotics are absent in the GI tract during C. diff infection, the chances of patient survival is zero.  This is because of the excess immune stimulation and incurable damage to the epithelial cell barrier of the gastrointestinal tract caused by C. diff bacteria.  The results also revealed, without any doubt, as of to-datethe latest discovery of Dr. M.S. Reddy’s Multiple Mixed Strain Probiotic Therapy is the best way to cure the deadly hospital acquired infections affecting millions of people around the world, with high degree of mortality.  This has been attested by several practicng medical professionals and scientists around the world (Reddy and Reddy, 2017).

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