Characterization of protein-protein interactions between rice viruses and vector insects

Planthoppers are the most notorious rice pests,because they transmit various rice viruses in a persistent-propagative manner.Protein–protein interactions(PPIs)between virus and vector are crucial for virus transmission by vector insects.However,the number of known PPIs for pairs of rice viruses and planthoppers is restricted by low throughput research methods.In this study,we applied DeNovo,a virus-host sequence-based PPI predictor,to predict potential PPIs at a genome-wide scale between three planthoppers and five rice viruses.PPIs were identified at two different confidence thresholds,referred to as low and high modes.The number of PPIs for the five planthopper-virus pairs ranged from 506 to 1985 in the low mode and from 1254 to 4286 in the high mode.After eliminating the“one-too-many”redundant interacting information,the PPIs with unique planthopper proteins were reduced to 343–724 in the low mode and 758–1671 in the high mode.Homologous analysis showed that 11 sets and 31 sets of homologous planthopper proteins were shared by all planthopper-virus interactions in the two modes,indicating that they are potential conserved vector factors essential for transmission of rice viruses.Ten PPIs between small brown planthopper and rice stripe virus(RSV)were verified using glutathione-S-transferase(GST)/His-pull down or co-immunoprecipitation assay.Five of the ten PPIs were proven positive,and three of the five SBPH proteins were confirmed to interact with RSV.The predicted PPIs provide new clues for further studies of the complicated relationship between rice viruses and their vector insects.

Ecology and management of Bactericera cockerelli and Candidatus Liberibacter solanacearum in New Zealand

The psyllid Bactericera cockerelli was first reported in New Zealand in 2006 and spread quickly throughout all potato growing regions.In 2009,B.cockerelli was associated with the plant pathogenic bacterium Candidatus Liberibacter solanacearum,the putative causal agent of zebra chip disease in potato.Both the psyllid and the bacterium have non-crop host plants which can serve as reservoirs when the crop is not available.Growers apply different management strategies that fit integrated pest management programmes to manage B.cockerelli and subsequently lower incidence of zebra chip disease in potato crops.Despite best management efforts,complete control of B.cockerelli and zero incidence of zebra chip disease are not achievable at the current time.

Cotton (Gossypium hirsutum L.) Boll Rot and Associated Microorganisms in South Texas Fields

A rise in cotton boll rot in south Texas has been generally associated with increased yield losses. Here, we measured boll rot incidence during two growing seasons (2011 and 2012) at a south Texas (Kleberg County) research farm Variety Trial and in producer fields. The Variety Trial was conducted to compare boll rot susceptibility between five current cultivars. The commercial fields surveyed were located along the Coastal Bend (Wharton County) and Rio Grande Valley regions (Cameron and Willacy Counties). Bolls with evidence of external damage potentially inflicted by piercing-sucking insect vectors were dissected for disease detection and plated for microorganism isolation and characterization. Microbial isolates were putatively identified based on standard fatty acid methyl ester profile analysis. In the Variety Trial, the highest incidence of disease occurred in July for both growing seasons, and significant differences in susceptibility to boll rot between cultivars were determined (P Bacillus spp. as a potential and prevalent causative agent(s).

Autophagy mediates a direct synergistic interaction during cotransmission of two distinct arboviruses by insect vectors

Multiple viral infections in insect vectors with synergistic effects are common in nature,but the underlying mechanism remains elusive.Here,we find that rice gall dwarf reovirus(RGDV)facilitates the transmission of rice stripe mosaic rhabdovirus(RSMV)by co-infected leafhopper vectors.RSMV nucleoprotein(N)alone activates complete anti-viral autophagy,while RGDV nonstructural protein Pns11 alone induces pro-viral incomplete autophagy.In co-infected vectors,RSMVexploits Pns11-induced autophagosomes to assemble enveloped virions via N-Pns11-ATG5 interaction.Furthermore,RSMV could effectively propagate in Sf9 cells.Expression of Pns11 in Sf9 cells or leafhopper vectors causes the recruitment of N from the ER to Pns11-induced autophagosomes and inhibits N-induced complete autophagic flux,finally facilitating RSMV propagation.In summary,these results demonstrate a previously unappreciated role of autophagy in the regulation of the direct synergistic interaction during co-transmission of two distinct arboviruses by insect vectors and reveal the functional importance of virus-induced autophagosomes in rhabdovirus assembly.

Polyamine-metabolizing enzymes are activated to promote the proper assembly of rice stripe mosaic virus in insect vectors

Both viruses and host cells compete for intracellular polyamines for efficient propagation.Currently,how the key polyamine-metabolizing enzymes,including ornithine decarboxylase 1(ODC1)and its antizyme 1(OAZ1),are activated to co-ordinate viral propagation and polyamine biosynthesis remains unknown.Here,we report that the matrix protein of rice stripe mosaic virus(RSMV),a cytorhabdovirus,directly hijacks OAZ1 to ensure the proper assembly of rigid bacilliform non-enveloped virions in leafhopper vector.Viral matrix protein effectively competes with ODC1 to bind to OAZ1,and thus,the ability of OAZ1 to target and mediate the degradation of ODC1 is significantly inhibited during viral propagation,which finally promotes polyamines production.Thus,OAZ1 and ODC1 are activated to synergistically promote viral persistent propagation and polyamine biosynthesis in viruliferous vectors.Our data suggest that it is a novel mechanism for rhabdovirus to exploit OAZ1 for facilitating viral assembly.

Insect transmission of plant viruses： Multilayered interactions optimize viral propagation

By serving as vectors of transmission, insects play a key role in the infection cycle of many plant viruses. Viruses use sophisticated transmission strategies to overcome the spatial barrier separating plants and the impediment imposed by the plant cell wall. Interactions among insect vectors, viruses, and host plants mediate transmission by integrating all organizational levels, from molecules to populations. Best-examined on the molecular scale are two basic transmission modes wherein virus-vector interactions have been well characterized. Whereas association of virus particles with specific sites in the vector＇s mouthparts or in alimentary tract regions immediately posterior to them is required for noncirculative transmission, the cycle of particles through the vector body is necessary for circulative transmission. Virus transmission is also determined by interactions that are associated with changes in vector feeding behaviors and with alterations in plant host＇s morphology and/or metabolism that favor the attraction or deterrence of vectors. A recent concept in virus-host-vector interactions proposes that when vectors land on infected plants, vector elicitors and effectors ＂inform＂ the plants of the confluence of interacting entities and trigger signaling pathways and plant defenses. Simultaneously, the plant responses may also influence virus acquisition and inoculation by vectors. Over- all, a picture is emerging where transmission depends on multilayered virus-vector-host interactions that define the route of a virus through the vector, and on the manipulation of the host and the vector. These interactions guarantee virus propagation until one or more of the interactants undergo changes through evolution or are halted by environmental interventions.

HEMIPTERAN-TRANSMITTED PLANT VIRUSES: RESEARCH PROGRESS AND CONTROL STRATEGIES

About 80% of plant viruses are transmitted by specific insect vectors, especiallyhemipterans with piercing-sucking mouthparts. Many virus-transmitting insectsare also important crop pests that cause considerable losses in crop production.This review summarizes the latest research findings on the interactions betweenplant viruses and insect vectors and analyzes the key factors affecting insecttransmission of plant viruses from the perspectives of insect immunity, insectfeeding, and insect symbiotic microorganisms. Additionally, by referring to thelatest applications for blocking the transmission of animal viruses, potentialcontrol strategies to prevent the transmission of insect-vectored plant virusesusing RNAi technology, gene editing technology, and CRISPR/Cas9 + gene-driventechnology are discussed.

A reproducible and sensitive method for generating high-quality transcriptomes from single whitefly salivary glands and other low-input tissues

Transcriptomic studies are an important tool for understanding the molecular pathways underlying host plant use by agricultural pests,including vectors of damaging plant pathogens.Thus far,bulk RNA-Seq has been the main approach for non-model insects.This method relies on pooling large numbers of whole organisms or hundreds of individually dissected organs.The latter approach is logistically challenging,may introduce artifacts of handling and storage,and is not compatible with biological replication.Here,we tested an approach to generate transcriptomes of individual salivary glands and other low-input body tissues from whiteflies(Bemisia tabaci MEAM1),which are major vectors of plant viruses.By comparing our outputs to published bulk RNA-Seq datasets for whole whitefly bodies and pools of salivary glands,we demonstrate that this approach recovers similar numbers of transcripts relative to bulk RNA-Seq in a tissue-specific manner,and for some metrics,exceeds performance of bulk tissue RNA-Seq.Libraries generated from individual salivary glands also yielded additional novel transcripts not identified in pooled salivary gland datasets,and had hundreds of enriched transcripts when compared with whole head tissues.Overall,our study demonstrates that it is feasible to produce high quality,replicated transcriptomes of whitefly salivary glands and other low-input tissues.We anticipate that our approach will expand hypothesis-driven research on salivary glands of whiteflies and other Hemiptera,thus enabling novel control strategies to disrupt feeding and virus transmission.