Viral RNA polymerase as a SUMOylation decoy inhibits RNA quality control to promote potyvirus infection.

Potyvirids are the largest group of plant RNA viruses. Pelota, a core component of RNA quality controls (RQC), promotes the degradation of potyvirids' genomic RNA by recognizing a specific GA motif. Here we demonstrate that the viral RNA-dependent RNA polymerase, NIb, acts as a SUMOylation decoy to effectively reduce Pelota SUMOylation by competing with SCE1 to inhibit Pelota-mediated RQC.

Coupling clearing and hybridization chain reaction approaches to investigate gene expression in organs inside intact insect heads.

Detecting RNA molecules within their natural environment inside intact arthropods has long been challenging, particularly in small organisms covered by a tanned and pigmented cuticle. Here, we have developed a methodology that enables high-resolution analysis of the spatial distribution of transcripts of interest without having to dissect tiny organs or tissues, thereby preserving their integrity. We have combined an in situ amplification approach based on hybridization chain reaction, which enhances the signal-to-noise ratio, and a clearing approach that allows the visualization of inner organs beneath the cuticle.

Role of Acrostyle Cuticular Proteins in the Retention of an Aphid Salivary Effector.

To avoid the activation of plant defenses and ensure sustained feeding, aphids are assumed to use their mouthparts to deliver effectors into plant cells. A recent study has shown that effectors detected near feeding sites are differentially distributed in plant tissues. However, the precise process of effector delivery into specific plant compartments is unknown.

Transcriptomic, proteomic and ultrastructural studies on salinity-tolerant Aedes aegypti in the context of rising sea levels and arboviral disease epidemiology.

Background: Aedes aegypti mosquito, the principal global vector of arboviral diseases, lays eggs and undergoes larval and pupal development to become adult mosquitoes in fresh water (FW). It has recently been observed to develop in coastal brackish water (BW) habitats of up to 50% sea water, and such salinity tolerance shown to be an inheritable trait. Genomics of salinity tolerance in Ae.

Insect Mouthpart Transcriptome Unveils Extension of Cuticular Protein Repertoire and Complex Organization.

Insects have developed intriguing cuticles with very specific structures and functions, including microstructures governing their interactions with transmitted microbes, such as in aphid mouthparts harboring virus receptors within such microstructures. Here, we provide the first transcriptome analysis of an insect mouthpart cuticle ("retort organs" [ROs], the stylets' precursors). This analysis defined stylets as a complex composite material.

An integrated protocol for targeted mutagenesis with CRISPR-Cas9 system in the pea aphid.

CRISPR-Cas9 technology is a very efficient functional analysis tool and has been developed in several insects to edit their genome through injection of eggs with guide RNAs targeting coding sequences of genes of interest. However, its implementation in aphids is more challenging. Aphids are major pests of crops worldwide that alternate during their life cycle between clonality and sexual reproduction.

Insect cuticular proteins and their role in transmission of phytoviruses.

Many viruses of agricultural importance are transmitted to host plants via insect vectors. Characterizing virus-vector interactions at the molecular level is essential if we are to fully understand the transmission mechanisms involved and develop new strategies to control viral spread. Hitherto, insect proteins involved in virus transmission have been characterized only poorly.

Identification of Plant Virus Receptor Candidates in the Stylets of Their Aphid Vectors.

Plant viruses transmitted by insects cause tremendous losses in most important crops around the world. The identification of receptors of plant viruses within their insect vectors is a key challenge to understanding the mechanisms of transmission and offers an avenue for future alternative control strategies to limit viral spread. We here report the identification of two cuticular proteins within aphid mouthparts, and we provide experimental support for the role of one of them in the transmission of a noncirculative virus.

Fasting alters aphid probing behaviour but does not universally increase the transmission rate of non-circulative viruses.

A fasting period prior to non-circulative virus acquisition has been shown to increase the rate of transmission by aphids. However, this effect has only been studied for a few virus-vector combinations, and there are contradictory results in the literature as to the role of fasting on virus acquisition. We analysed the influence of fasting on the transmission of three non-circulative viruses, , and , by two aphid vector species: Sulzer (Hemiptera: Aphididae) and Glover (Hemiptera: Aphididae).

Plant infection by two different viruses induce contrasting changes of vectors fitness and behavior.

Insect-vectored plant viruses can induce changes in plant phenotypes, thus influencing plant-vector interactions in a way that may promote their dispersal according to their mode of transmission (i.e., circulative vs.

Proteomic composition of the acrostyle: Novel approaches to identify cuticular proteins involved in virus-insect interactions.

The acrostyle is a distinct anatomical region present on the cuticle at the inner face of the common food/salivary canal at the tip of aphid maxillary stylets. This conserved structure is of particular interest as it harbors the protein receptors of at least 1 plant virus, Cauliflower mosaic virus, and presumably has other roles in plant-insect interactions. Previously we reported immunolabeling of a highly conserved motif of cuticular proteins from the CPR family (named for the presence of a Rebers and Riddiford consensus) within the acrostyle.

Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species.

Background: The prevailing paradigm of host-parasite evolution is that arms races lead to increasing specialisation via genetic adaptation. Insect herbivores are no exception and the majority have evolved to colonise a small number of closely related host species. Remarkably, the green peach aphid, Myzus persicae, colonises plant species across 40 families and single M.

The genomes of many yam species contain transcriptionally active endogenous geminiviral sequences that may be functionally expressed.

Endogenous viral sequences are essentially 'fossil records' that can sometimes reveal the genomic features of long extinct virus species. Although numerous known instances exist of single-stranded DNA (ssDNA) genomes becoming stably integrated within the genomes of bacteria and animals, there remain very few examples of such integration events in plants. The best studied of these events are those which yielded the geminivirus-related DNA elements found within the nuclear genomes of various species.

Localizing viruses in their insect vectors.

The mechanisms and impacts of the transmission of plant viruses by insect vectors have been studied for more than a century. The virus route within the insect vector is amply documented in many cases, but the identity, the biochemical properties, and the structure of the actual molecules (or molecule domains) ensuring compatibility between them remain obscure. Increased efforts are required both to identify receptors of plant viruses at various sites in the vector body and to design competing compounds capable of hindering transmission.

New research horizons in vector-transmission of plant viruses.

Understanding the mechanisms controlling vector-transmission of plant viruses requires integrating information from at least three different viewpoints: virus-vector interactions, plant-vector interactions and virus-plant interactions. While some of these aspects have been covered by past and present investigations, others have been bypassed completely, because of technical bottlenecks or conceptual lacunas. Here, we highlight recent advances and needs in hitherto poorly documented aspects of vector transmission, such as characterization of the vector molecules responsible for initial viral recognition, and the role of vector saliva in inoculation and initial onset of infection in a new plant.

[Transmission of a complex: not so simple. The case of Cauliflower mosaic virus].

Transmission by a vector is a common feature among viruses, especially plant viruses. While animal arboviruses infect literally their vector ("biological transmission"), plant viruses are mostly transmitted "mechanically". This mode of transmission is seemingly quite simple - the virus contaminates the vector mouthparts and subsequently is mechanically inoculated into new healthy hosts.

Aphids as transport devices for plant viruses.

Plant viruses have evolved a wide array of strategies to ensure efficient transfer from one host to the next. Any organism feeding on infected plants and traveling between plants can potentially act as a virus transport device. Such organisms, designated vectors, are found among parasitic fungi, root nematodes and plant-feeding arthropods, particularly insects.

Structural insights into the molecular mechanisms of cauliflower mosaic virus transmission by its insect vector.

Cauliflower mosaic virus (CaMV) is transmitted from plant to plant through a seemingly simple interaction with insect vectors. This process involves an aphid receptor and two viral proteins, P2 and P3. P2 binds to both the aphid receptor and P3, itself tightly associated with the virus particle, with the ensemble forming a transmissible viral complex.

The "acrostyle": a newly described anatomical structure in aphid stylets.

The recent demonstration that a plant virus could be retained on protein receptors located exclusively in a small area inside the common duct at the tip of aphid maxillary stylets indicated the possible existence of a distinct anatomical structure at this level. Since no distinct feature within the common duct of any aphid species has ever been reported in the literature, we first carefully re-examined the distal extremity of the maxillary stylets of Acyrthosiphon pisum using transmission- and scanning-electron microscopy. Here, we describe an area of the cuticle surface displaying a different structure that is limited to a "band" paving the bottom of the common duct in each opposing maxillary stylet.

A role for plant microtubules in the formation of transmission-specific inclusion bodies of Cauliflower mosaic virus.

Interactions between microtubules and viruses play important roles in viral infection. The best-characterized examples involve transport of animal viruses by microtubules to the nucleus or other intracellular destinations. In plant viruses, most work to date has focused on interaction between viral movement proteins and the cytoskeleton, which is thought to be involved in viral cell-to-cell spread.

A protein key to plant virus transmission at the tip of the insect vector stylet.

Hundreds of species of plant viruses, many of them economically important, are transmitted by noncirculative vector transmission (acquisition by attachment of virions to vector mouthparts and inoculation by subsequent release), but virus receptors within the vector remain elusive. Here we report evidence for the existence, precise location, and chemical nature of the first receptor for a noncirculative virus, cauliflower mosaic virus, in its insect vector. Electron microscopy revealed virus-like particles in a previously undescribed anatomical zone at the extreme tip of the aphid maxillary stylets.

A single amino acid position in the helper component of cauliflower mosaic virus can change the spectrum of transmitting vector species.

Viruses frequently use insect vectors to effect rapid spread through host populations. In plant viruses, vector transmission is the major mode of transmission, used by nearly 80% of species described to date. Despite the importance of this phenomenon in epidemiology, the specificity of the virus-vector relationship is poorly understood at both the molecular and the evolutionary level, and very limited data are available on the precise viral protein motifs that control specificity.