The Immunity Regulator BAK1 Contributes to Resistance Against Diverse RNA Viruses

The plant's innate immune system detects potential biotic threats through recognition of microbe-associated molecular patterns (MAMPs) or danger-associated molecular patterns (DAMPs) by pattern recognition receptors (PRR). A central regulator of pattern-triggered immunity (PTI) is the BRI1-associated kinase 1 (BAK1), which undergoes complex formation with PRR upon ligand binding. Although viral patterns inducing PTI are well known from animal systems, nothing similar has been reported for plants. Rather, antiviral defense in plants is thought to be mediated by post-transcriptional gene silencing of viral RNA or through effector-triggered immunity, i.e., recognition of virus-specific effectors by resistance proteins. Nevertheless, infection by compatible viruses can also lead to the induction of defense gene expression, indicating that plants may also recognize viruses through PTI. Here, we show that PTI, or at least the presence of the regulator BAK1, is important for antiviral defense of Arabidopsis plants. Arabidopsis bak1 mutants show increased susceptibility to three different RNA viruses during compatible interactions. Furthermore, crude viral extracts but not purified virions induce several PTI marker responses in a BAK1-dependent manner. Overall, we conclude that BAK1-dependent PTI contributes to antiviral resistance in plants.

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Binding and processing of small dsRNA molecules by the class 1 RNase III protein encoded by sweet potato chlorotic stunt virus

Journal of General Virology ◽

10.1099/vir.0.058693-0 ◽

2014 ◽

Vol 95 (2) ◽

pp. 486-495 ◽

Cited By ~ 8

Author(s):

Isabel Weinheimer ◽

Kajohn Boonrod ◽

Mirko Moser ◽

Michael Wassenegger ◽

Gabi Krczal ◽

...

Keyword(s):

Sweet Potato ◽

Transcriptional Gene Silencing ◽

Specific Class ◽

Dependent Manner ◽

Small Interfering Rnas ◽

Rnase Iii ◽

Potato Plants ◽

Post Transcriptional Gene Silencing ◽

Class 1

Sweet potato chlorotic stunt virus (SPCSV; genus Crinivirus, family Closteroviridae) causes heavy yield losses in sweet potato plants co-infected with other viruses. The dsRNA-specific class 1 RNase III–like endoribonuclease (RNase3) encoded by SPCSV suppresses post-transcriptional gene silencing and eliminates antiviral defence in sweet potato plants in an endoribonuclease activity-dependent manner. RNase3 can cleave long dsRNA molecules, synthetic small interfering RNAs (siRNAs), and plant- and virus-derived siRNAs extracted from sweet potato plants. In this study, conditions for efficient expression and purification of enzymically active recombinant RNase3 were established. Similar to bacterial class 1 RNase III enzymes, RNase3-Ala (a dsRNA cleavage-deficient mutant) bound to and processed double-stranded siRNA (ds-siRNA) as a dimer. The results support the classification of SPCSV RNase3 as a class 1 RNase III enzyme. There is little information about the specificity of RNase III enzymes on small dsRNAs. In vitro assays indicated that ds-siRNAs and microRNAs (miRNAs) with a regular A-form conformation were cleaved by RNase3, but asymmetrical bulges, extensive mismatches and 2′-O-methylation of ds-siRNA and miRNA interfered with processing. Whereas Mg2+ was the cation that best supported the catalytic activity of RNase3, binding of 21 nt small dsRNA molecules was most efficient in the presence of Mn2+. Processing of long dsRNA by RNase3 was efficient at pH 7.5 and 8.5, whereas ds-siRNA was processed more efficiently at pH 8.5. The results revealed factors that influence binding and processing of small dsRNA substrates by class 1 RNase III in vitro or make them unsuitable for processing by the enzyme.

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RNA viruses as inducers, suppressors and targets of post-transcriptional gene silencing

Plant Gene Silencing ◽

10.1007/978-94-011-4183-3_13 ◽

2000 ◽

pp. 175-186 ◽

Cited By ~ 1

Author(s):

Rajendra Marathe ◽

Radhamani Anandalakshmi ◽

Trent H. Smith ◽

Gail J. Pruss ◽

Vicki B. Vance

Keyword(s):

Gene Silencing ◽

Rna Viruses ◽

Transcriptional Gene Silencing ◽

Post Transcriptional Gene Silencing

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Breaking Bad News: Dynamic Molecular Mechanisms of Wound Response in Plants

Frontiers in Plant Science ◽

10.3389/fpls.2020.610445 ◽

2020 ◽

Vol 11 ◽

Author(s):

Isaac Vega-Muñoz ◽

Dalia Duran-Flores ◽

Álvaro Daniel Fernández-Fernández ◽

Jefri Heyman ◽

Andrés Ritter ◽

...

Keyword(s):

Molecular Mechanisms ◽

Wound Response ◽

Surrounding Tissue ◽

Defense Gene Expression ◽

Defense Gene ◽

Breaking Bad ◽

Damage Recognition ◽

Pathogen Colonization ◽

Recognition And Response ◽

Molecular Patterns

Recognition and repair of damaged tissue are an integral part of life. The failure of cells and tissues to appropriately respond to damage can lead to severe dysfunction and disease. Therefore, it is essential that we understand the molecular pathways of wound recognition and response. In this review, we aim to provide a broad overview of the molecular mechanisms underlying the fate of damaged cells and damage recognition in plants. Damaged cells release the so-called damage associated molecular patterns to warn the surrounding tissue. Local signaling through calcium (Ca2+), reactive oxygen species (ROS), and hormones, such as jasmonic acid, activates defense gene expression and local reinforcement of cell walls to seal off the wound and prevent evaporation and pathogen colonization. Depending on the severity of damage, Ca2+, ROS, and electrical signals can also spread throughout the plant to elicit a systemic defense response. Special emphasis is placed on the spatiotemporal dimension in order to obtain a mechanistic understanding of wound signaling in plants.

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Antiviral innate immune response of RNA interference

The Journal of Infection in Developing Countries ◽

10.3855/jidc.4187 ◽

2014 ◽

Vol 8 (07) ◽

pp. 804-810 ◽

Cited By ~ 8

Author(s):

Abubaker Sidahmed ◽

Shaza Abdalla ◽

Salahedin Mahmud ◽

Bruce Wilkie

Keyword(s):

Immune Response ◽

Rna Interference ◽

Viral Infection ◽

Gene Silencing ◽

Immune Defense ◽

Innate Immune ◽

Transcriptional Gene Silencing ◽

Antiviral Defense ◽

Post Transcriptional Gene Silencing ◽

Short Period

RNA interference (RNAi) is an ancient, natural process conserved among species from different kingdoms. RNAi is a transcriptional and post-transcriptional gene silencing mechanism in which, double-stranded RNA or hairpin RNA is cleaved by an RNase III-type enzyme called Dicer into small interfering RNA duplex. This subsequently directs sequence-specific, homology dependent, Watson-Crick base-pairing post-transcriptional gene silencing by binding to its complementary RNA and initiating its elimination through degradation or by persuading translational inhibition. In plants, worms, and insects, RNAi is the main and strong antiviral defense mechanism. It is clear that RNAi silencing, contributes in restriction of viral infection in vertebrates. In a short period, RNAi has progressed to become a significant experimental tool for the analysis of gene function and target validation in mammalian systems. In addition, RNA silencing has then been found to be involved in translational repression, transcriptional inhibition, and DNA degradation. RNAi machinery required for robust RNAi-mediated antiviral response are conserved throughout evolution in mammals and plays a crucial role in antiviral defense of invertebrates, but despite these important functions RNAi contribution to mammalian antiviral innate immune defense has been underestimated and disputed. In this article, we review the literature concerning the roles of RNAi as components of innate immune system in mammals and how, the RNAi is currently one of the most hopeful new advances toward disease therapy. This review highlights the potential of RNAi as a therapeutic strategy for viral infection and gene regulation to modulate host immune response to viral infection.

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Functional dissection of the ARGONAUTE7 promoter

10.1101/392910 ◽

2018 ◽

Author(s):

J. Steen Hoyer ◽

Jose L. Pruneda-Paz ◽

Ghislain Breton ◽

Mariah A. Hassert ◽

Emily E. Holcomb ◽

...

Keyword(s):

Binding Sites ◽

Rna Silencing ◽

Leaf Shape ◽

Effector Proteins ◽

Transcriptional Gene Silencing ◽

Antiviral Defense ◽

Post Transcriptional Gene Silencing ◽

And Function ◽

Central Effector ◽

Ranked List

AbstractARGONAUTES are the central effector proteins of RNA silencing which bind target transcripts in a small RNA-guided manner. Arabidopsis thaliana has ten ARGONAUTE (AGO) genes, with specialized roles in RNA-directed DNA methylation, post-transcriptional gene silencing, and antiviral defense. To better understand specialization among AGO genes at the level of transcriptional regulation we tested a library of 1497 transcription factors for binding to the promoters of AGO1, AGO10, and AGO7 using yeast 1-hybrid assays. A ranked list of candidate DNA-binding TFs revealed binding of the AGO7 promoter by a number of proteins in two families: the miR156-regulated SPL family and the miR319-regulated TCP family, both of which have roles in developmental timing and leaf morphology. Possible functions for SPL and TCP binding are unclear: we showed that these binding sites are not required for the polar expression pattern of AGO7, nor for the function of AGO7 in leaf shape. Normal AGO7 transcription levels and function appear to depend instead on an adjacent 124-bp region. Progress in understanding the structure of this promoter may aid efforts to understand how the conserved AGO7-triggered TAS3 pathway functions in timing and polarity.

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Phosphatidylcholines from Pieris brassicae eggs activate an immune response in Arabidopsis

eLife ◽

10.7554/elife.60293 ◽

2020 ◽

Vol 9 ◽

Author(s):

Elia Stahl ◽

Théo Brillatz ◽

Emerson Ferreira Queiroz ◽

Laurence Marcourt ◽

André Schmiesing ◽

...

Keyword(s):

Pieris Brassicae ◽

Fatty Acyl ◽

Cell Surface Receptor ◽

Ligand Specificity ◽

Defense Gene Expression ◽

Insect Eggs ◽

Defense Gene ◽

Surface Receptor ◽

Acyl Chains ◽

Molecular Patterns

Recognition of conserved microbial molecules activates immune responses in plants, a process termed pattern-triggered immunity (PTI). Similarly, insect eggs trigger defenses that impede egg development or attract predators, but information on the nature of egg-associated elicitors is scarce. We performed an unbiased bioactivity-guided fractionation of eggs of the butterfly Pieris brassicae. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry of active fractions led to the identification of phosphatidylcholines (PCs). PCs are released from insect eggs, and they induce salicylic acid and H2O2 accumulation, defense gene expression and cell death in Arabidopsis, all of which constitute a hallmark of PTI. Active PCs contain primarily C16 to C18-fatty acyl chains with various levels of desaturation, suggesting a relatively broad ligand specificity of cell-surface receptor(s). The finding of PCs as egg-associated molecular patterns (EAMPs) illustrates the acute ability of plants to detect conserved immunogenic patterns from their enemies, even from seemingly passive structures such as eggs.

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Molecular Crosstalk Between PAMP-Triggered Immunity and Photosynthesis

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-11-11-0301 ◽

2012 ◽

Vol 25 (8) ◽

pp. 1083-1092 ◽

Cited By ~ 97

Author(s):

Vera Göhre ◽

Alexandra M. E. Jones ◽

Jan Sklenář ◽

Silke Robatzek ◽

Andreas P. M. Weber

Keyword(s):

Defense Responses ◽

Innate Immune ◽

Energy Costs ◽

Defense Gene Expression ◽

Defense Gene ◽

Fluorescence Measurements ◽

Species Production ◽

Molecular Patterns ◽

Intrinsic Component ◽

Molecular Crosstalk

The innate immune system allows plants to respond to potential pathogens in an appropriate manner while minimizing damage and energy costs. Photosynthesis provides a sustained energy supply and, therefore, has to be integrated into the defense against pathogens. Although changes in photosynthetic activity during infection have been described, a detailed and conclusive characterization is lacking. Here, we addressed whether activation of early defense responses by pathogen-associated molecular patterns (PAMPs) triggers changes in photosynthesis. Using proteomics and chlorophyll fluorescence measurements, we show that activation of defense by PAMPs leads to a rapid decrease in nonphotochemical quenching (NPQ). Conversely, NPQ also influences several responses of PAMP-triggered immunity. In a mutant impaired in NPQ, apoplastic reactive oxygen species production is enhanced and defense gene expression is differentially affected. Although induction of the early defense markers WRKY22 and WRKY29 is enhanced, induction of the late markers PR1 and PR5 is completely abolished. We propose that regulation of NPQ is an intrinsic component of the plant's defense program.

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Trigger and suppression of antiviral defenses by grapevine Pinot gris virus (GPGV): novel insights into virus-host interaction

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-04-21-0078-r ◽

2021 ◽

Author(s):

Giulia Tarquini ◽

Laura Pagliari ◽

Paolo Ermacora ◽

Rita Musetti ◽

Giuseppe Firrao

Keyword(s):

Rna Silencing ◽

Infectious Clone ◽

Transcriptional Gene Silencing ◽

Antiviral Defense ◽

Small Interfering Rnas ◽

Host Interaction ◽

Post Transcriptional Gene Silencing ◽

Gene Expression Analyses ◽

Grapevine Pinot Gris Virus

Grapevine Pinot gris virus (GPGV) is an emerging trichovirus that has been putatively associated with a novel grapevine disease known as grapevine leaf mottling and deformation (GLMD). Yet the role of GPGV in GLMD disease is poorly understood since it has been detected both in symptomatic and symptomless grapevines. We exploited a recently constructed GPGV infectious clone (pRI::GPGV-vir) to induce an antiviral response in Nicotiana benthamiana plants. In silico prediction of virus-derived small interfering RNAs (vsiRNAs) and gene expression analyses revealed the involvement of DCL4, AGO5 and RDR6 genes during GPGV infection, suggesting the activation of the post-transcriptional gene-silencing (PTGS) pathway as a plant antiviral defense. PTGS suppression assays in transgenic N. benthamiana 16c plants revealed the ability of the GPGV coat protein to suppress RNA silencing. This work provides novel insights on the interaction between GPGV and its host, revealing the ability of the virus to trigger and suppress antiviral RNA silencing.

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