Southern rice black-streaked dwarf virus induces incomplete autophagy for persistence in gut epithelial cells of its vector insect

Characterizing the impact of CPSF30 gene disruption on TuMV infection in Arabidopsis thaliana

CPSF30, a key polyadenylation factor, also serves as an m6A reader, playing a crucial role in determining RNA fate post-transcription. While its homologs mammals are known to be vital for viral replication and immune evasion, the full scope of CPSF30 in plant, particular in viral regulation, remains less explored. Our study demonstrates that CPSF30 significantly facilitates the infection of turnip mosaic virus (TuMV) in Arabidopsis thaliana, as evidenced by infection experiments on the engineered cpsf30 mutant. Among the two isoforms, CPSF30-L, which were characterized with m6A binding activity, emerged as the primary isoform responding to TuMV infection. Analysis of m6A components revealed potential involvement of the m6A machinery in regulating TuMV infection. In contrast, CPSF30-S exhibited distinct subcellular localization, coalescing with P-body markers (AtDCP1 and AtDCP2) in cytoplasmic granules, suggesting divergent regulatory mechanisms between the isoforms. Furthermore, comprehensive mRNA-Seq and miRNA-Seq analysis of Col-0 and cpsf30 mutants revealed global transcriptional reprogramming, highlighting CPSF30's role in selectively modulating gene expression during TuMV infection. In conclusion, this research underscores CPSF30's critical role in the TuMV lifecycle and sets the stage for further exploration of its function in plant viral regulation.

Exploring the shared pathogenic strategies of independently evolved effectors across distinct plant viruses

Plants have developed very diverse strategies to defend themselves against viral pathogens, among which plant hormones play pivotal roles. In response, some viruses have also deployed multifunctional viral effectors that effectively hijack key component hubs to counter or evade plant immune surveillance. Although significant progress has been made toward understanding counter-defense strategies that manipulate plant hormone regulatory molecules, these efforts have often been limited to an individual virus or specific host target/pathway. This review provides new insights into broad-spectrum antiviral responses in rice triggered by key components of phytohormone signaling, and highlights the common features of counter-defense strategies employed by distinct rice-infecting RNA viruses. These strategies involve the secretion of multifunctional virulence effectors that target the sophisticated phytohormone system, dampening immune responses by engaging with the same host targets. Additionally, the review provides an in-depth exploration of various viral effectors, emphasizing tertiary structure-based research and shared host targets. Understanding these conserved characteristics in detail may pave the way for molecular drug design, opening new opportunities to enhance broad-spectrum antiviral trials through precise engineering.

Ben-JNK signaling is required for host mortality during Periplaneta fuliginosa densovirus infection

BACKGROUND

Cockroaches are widely acknowledged as significant vectors of pathogenic microorganisms. The Periplaneta fuliginosa densovirus (PfDNV) infects the smoky-brown cockroach P. fuliginosa and causes host mortality, which identifies the PfDNV as a species-specific and environmentally friendly biopesticide. However, although the biochemical characterization of PfDNV has been extensively studied, the immune response against PfDNV remains largely unclear.

RESULTS

Here, we investigated the replication of PfDNV and its associated pathological phenotype in the foregut and hindgut. Consequently, we dissected and performed transcriptome sequencing on the foregut, midgut, and hindgut separately. We revealed the up-regulation of immune response signaling pathway c-Jun N-terminal kinase (JNK) and apoptosis in response to viral infection. Furthermore, knockdown of the JNK upstream gene Ben resulted in a decrease in virus titer and delayed host mortality.

CONCLUSION

Taken together, our findings provide evidence that the Ben-JNK signaling plays a crucial role in PfDNV infection, leading to excessive apoptosis in intestinal tissues and ultimately resulting in the death of the host. Our results indicated that the host response to PfDNV fosters viral infection, thereby increasing host lethality. This underscores the potential of PfDNV as a viable, environmentally friendly biopesticide. © 2024 Society of Chemical Industry.

Dual Guardians of Immunity: FoRab10 and FoRab29 in Frankliniella occidentalis Confer Resistance to Tomato Spotted Wilt Orthotospovirus

Rab GTPase is critical for autophagy processes and is implicated in insect immunity against viruses. In this study, we aimed to investigate the role of FoRabs in the autophagic regulation of antiviral defense against tomato spotted wilt orthotospovirus (TSWV) in Frankliniella occidentalis. Transcriptome analysis revealed the downregulation of FoRabs in viruliferous nymph and adults of F. occidentalis in response to TSWV infection. Manipulation of autophagy levels with 3-MA and Rapa treatments resulted in a 5- to 15-fold increase and a 38-64% decrease in viral titers, respectively. Additionally, interference with FoRab10 in nymphs and FoRab29 in adults led to a 20-90% downregulation of autophagy-related genes, a decrease in ATG8-II (an autophagy marker protein), and an increase in the TSWV titers by 1.5- to 2.5-fold and 1.3- to 2.0-fold, respectively. In addition, the leaf disk and the living plant methods revealed increased transmission rates of 20.8-41.6 and 68.3-88.3%, respectively. In conclusion, FoRab10 and FoRab29 play a role in the autophagic regulation of the antiviral defense in F. occidentalis nymphs and adults against TSWV, respectively. These findings offer insights into the intricate immune mechanisms functional in F. occidentalis against TSWV, suggesting potential targeted strategies for F. occidentalis and TSWV management.

Rice stripe mosaic virus hijacks rice heading-related gene to promote the overwintering of its insect vector

Rice stripe mosaic virus (RSMV) is an emerging pathogen which significantly reduces rice yields in the southern region of China. It is transmitted by the leafhopper Recilia dorsalis, which overwinters in rice fields. Our field investigations revealed that RSMV infection causes delayed rice heading, resulting in a large number of green diseased plants remaining in winter rice fields. This creates a favorable environment for leafhoppers and viruses to overwinter, potentially contributing to the rapid spread and epidemic of the disease. Next, we explored the mechanism by which RSMV manipulates the developmental processes of the rice plant. A rice heading-related E3 ubiquitin ligase, Heading date Associated Factor 1 (HAF1), was found to be hijacked by the RSMV-encoded P6. The impairment of HAF1 function affects the ubiquitination and degradation of downstream proteins, HEADING DATE 1 and EARLY FLOWERING3, leading to a delay in rice heading. Our results provide new insights into the development regulation-based molecular interactions between virus and plant, and highlights the importance of understanding virus-vector-plant tripartite interactions for effective disease management strategies.

The Spread of Southern Rice Black-Streaked Dwarf Virus Was Not Caused by Biological Changes in Vector Sogatella furcifera

The pandemic of Southern rice black-streaked dwarf virus (SRBSDV) in and after the late 2000s caused serious yield losses in rice in Southeast and East Asia. This virus was first recorded in China in 2001, but its exclusive vector insect, Sogatella furcifera, occurred there before then. To clarify the evolutionary origin of SRBSDV as the first plant virus transmitted by S. furcifera, we tested virus transmission using three chronological strains of S. furcifera, two of which were established before the first report of SRBSDV. When the strains fed on SRBSDV-infected rice plants were transferred to healthy rice plants, those established in 1989 and 1999 transmitted the virus to rice similarly to the strain established in 2010. SRBSDV quantification by RT-qPCR confirmed virus accumulation in the salivary glands of all three strains. Therefore, SRBSDV transmission by S. furcifera was not caused by biological changes in the vector, but probably by the genetic change of the virus from a closely related Fijivirus, Rice black-streaked dwarf virus, as suggested by ecological and molecular biological comparisons between the two viruses. This result will help us to better understand the evolutionary relationship between plant viruses and their vector insects and to better manage viral disease in rice cropping in Asia.

Introgression of OsAP47 by marker-assisted selection enhanced resistance against southern rice black-streaked dwarf virus disease

Southern rice black-streaked dwarf virus disease (SRBSDVD) is the most destructive viral disease in rice. In order to breeding resistant cultivars, Insertion-Deletion (InDel) markers were developed linked to OsAP47, the first isolated major resistance gene against SRBSDVD. Marker-assisted selection (MAS) was conducted to introduce this gene into the commercial variety. A rice line carrying homozygous resistance allele of OsAP47 was selected and named Kanghei No. 201 (KH201). Evaluated by artificial inoculation, KH201 showed significantly higher resistance than the recurrent parent Suxiu No.867 (SX867). And no significant differences were detected for KH201 in the yield-related components, including spikelets per panicle (SPP), ripened grains per panicle (RGPP), 1000-grain weight (TGW) and panicles per square meter (PPSM), leading to stable theoretical yield. The results indicated that introgression of OsAP47 improved rice resistance and can avoid yield losses produced by SRBSDVD. KH201 was demonstrated as a resistance material that could be used in rice breeding.

Complex interactions among insect viruses-insect vector-arboviruses

Insects are the host or vector of diverse viruses including those that infect vertebrates, plants, and fungi. Insect viruses reside inside their insect hosts and are vertically transmitted from parent to offspring. The insect virus-host relationship is intricate, as these viruses can impact various aspects of insect biology, such as development, reproduction, sex ratios, and immunity. Arthropod-borne viruses (arboviruses) that cause substantial global health or agricultural problems can also be vertically transmitted to insect vector progeny. Multiple infections with insect viruses and arboviruses are common in nature. Such coinfections involve complex interactions, including synergism, dependence, and antagonism. Recent studies have shed light on the influence of insect viruses on the competence of insect vectors for arboviruses. In this review, we focus on the biological effects of insect viruses on the transmission of arboviruses by insects. We also discuss the potential mechanisms by which insect viruses affect the ability of hosts to transmit arboviruses, as well as potential strategies for disease control through manipulation of insect viruses. Analyses of the interactions among insect vectors, insect viruses and arboviruses will provide new opportunities for development of innovative strategies to control arbovirus transmission.

Managing Super Pests: Interplay between Pathogens and Symbionts Informs Biocontrol of Whiteflies

Bemisia tabaci is distributed globally and incurs considerable economic and ecological costs as an agricultural pest and viral vector. The entomopathogenic fungus Metarhizium anisopliae has been known for its insecticidal activity, but its impacts on whiteflies are understudied. We investigated how infection with the semi-persistently transmitted Cucurbit chlorotic yellows virus (CCYV) affects whitefly susceptibility to M. anisopliae exposure. We discovered that viruliferous whiteflies exhibited increased mortality when fungus infection was present compared to non-viruliferous insects. High throughput 16S rRNA sequencing also revealed significant alterations of the whitefly bacterial microbiome diversity and structure due to both CCYV and fungal presence. Specifically, the obligate symbiont Portiera decreased in relative abundance in viruliferous whiteflies exposed to M. anisopliae. Facultative Hamiltonella and Rickettsia symbionts exhibited variability across groups but dominated in fungus-treated non-viruliferous whiteflies. Our results illuminate triangular interplay between pest insects, their pathogens, and symbionts-dynamics which can inform integrated management strategies leveraging biopesticides This work underscores the promise of M. anisopliae for sustainable whitefly control while laying the groundwork for elucidating mechanisms behind microbe-mediated shifts in vector competence.

A viral movement protein targets host catalases for 26S proteasome-mediated degradation to facilitate viral infection and aphid transmission in wheat

The infection of host plants by many different viruses causes reactive oxygen species (ROS) accumulation and yellowing symptoms, but the mechanisms through which plant viruses counteract ROS-mediated immunity to facilitate infection and symptom development have not been fully elucidated. Most plant viruses are transmitted by insect vectors in the field, but the molecular mechanisms underlying virus‒host-insect interactions are unclear. In this study, we investigated the interactions among wheat, barley yellow dwarf virus (BYDV), and its aphid vector and found that the BYDV movement protein (MP) interacts with both wheat catalases (CATs) and the 26S proteasome ubiquitin receptor non-ATPase regulatory subunit 2 homolog (PSMD2) to facilitate the 26S proteasome-mediated degradation of CATs, promoting viral infection, disease symptom development, and aphid transmission. Overexpression of the BYDV MP gene in wheat enhanced the degradation of CATs, which leading to increased accumulation of ROS and thereby enhanced viral infection. Interestingly, transgenic wheat lines overexpressing BYDV MP showed significantly reduced proliferation of wingless aphids and an increased number of winged aphids. Consistent with this observation, silencing of CAT genes also enhanced viral accumulation and reduced the proliferation of wingless aphids but increased the occurrence of winged aphids. In contrast, transgenic wheat plants overexpressing TaCAT1 exhibited the opposite changes and showed increases in grain size and weight upon infection with BYDV. Biochemical assays demonstrated that BYDV MP interacts with PSMD2 and promotes 26S proteasome-mediated degradation of TaCAT1 likely in a ubiquitination-independent manner. Collectively, our study reveals a molecular mechanism by which a plant virus manipulates the ROS production system of host plants to facilitate viral infection and transmission, shedding new light on the sophisticated interactions among viruses, host plants, and insect vectors.

Plant virology in the 21st century in China: Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security. Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years, including basic research and technologies for preventing and controlling plant viral diseases. Here, we review these milestones and advances, including the identification of new crop-infecting viruses, dissection of pathogenic mechanisms of multiple viruses, examination of multilayered interactions among viruses, their host plants, and virus-transmitting arthropod vectors, and in-depth interrogation of plant-encoded resistance and susceptibility determinants. Notably, various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants. We also recommend future plant virology studies in China.

Plant reoviruses hijack autophagy in insect vectors

Plant reoviruses, transmitted only by insect vectors, seriously threaten global cereal production. Understanding how insect vectors efficiently transmit the viruses is key to controlling the viral diseases. Autophagy commonly plays important roles in plant host defense against virus infection, but recent studies have shown that plant reoviruses can hijack the autophagy pathway in insect cells to enable their persistence in the insect and continued transmission to plants. Here, we summarize and discuss new insights on viral activation, evasion, regulation, and manipulation of autophagy within the insect vectors and the role of autophagy in virus survival in insect vectors. Deeper knowledge of the functions of autophagy in vectors may lead to novel strategies for blocking transmission of insect-borne plant viruses.