Rice Black-streaked Dwarf Virus Infection Research Articles

The miR184-3p targets neuron-specific ecdysone inducible protein 78 to promote rice black streaked dwarf virus propagation in its planthopper vector.

MicroRNAs (miRNAs) are non-coding RNAs that play a pivotal role in antiviral infection. The miR184-3p has been identified to promote rice black streaked dwarf virus (RBSDV) infection in vector Laodelphax striatellus, whether it targets other genes of L. striatellus to modulate RBSDV propagation remains unknown. We first analyzed the expression profiles of miR184-3p and its role in regulating RBSDV infection in L. striatellus. Then the candidate genes expression of miR184-3p were systemically analyzed with gain and loss function of miR184-3p, and the interaction of candidate gene, ecdysone inducible protein 78 (Eip78) with miR184-3p was verified by dual luciferase reporter assay. We found Eip78 is evolutionary conserved among agricultural pests and predominantly expressed in the central nervous system (CNS) of L. striatellus. Knockdown of Eip78 effectively increased RBSDV propagation and transmission. Blockade with Eip78 antibody or injection with Eip78 protein could significantly regulate RBSDV infection. Further analysis revealed that knockdown of Eip78 specifically suppresses RBSDV infection in the head part but not in the body part of L. striatellus. Besides, knockdown of ecdysone receptor (EcR) notably restricted Eip78 expression and increased RBSDV accumulation in L. striatellus. Taken together, we identified a novel target gene of miR184-3p, Eip78, a member of the ecdysone signaling pathway, and revealed the anti-RBSDV role of Eip78 in the CNS of L. striatellus. These results shed light on the interaction mechanisms of miRNAs, virus and ecdysone signaling pathway in insect vector. © 2024 Society of Chemical Industry.

MicroRNA750-3p Targets Processing of Precursor 7 to Suppress Rice Black-Streaked Dwarf Virus Propagation in Vector Laodelphax striatellus.

MicroRNAs (miRNAs) are non-coding RNAs, which, as members of the RNA interference pathway, play a pivotal role in antiviral infection. Almost 80% of plant viruses are transmitted by insect vectors; however, little is known about the interaction of the miRNAs of insect vectors with plant viruses. Here, we took rice black-streaked dwarf virus (RBSDV), a devastating virus to rice production in eastern Asia, and the small brown planthopper, (SBPH, Laodelphax striatellus) as a model to investigate the role of microRNA750-3p (miR750-3p) in regulating viral transmission. Our results showed that Ls-miR750-3p was downregulated in RBSDV-infected SBPH and predominately expressed in the midgut of SBPH. Injection with miR750-3p agomir significantly reduced viral accumulation, and the injection with the miR750-3p inhibitor, antagomir-750-3p, dramatically promoted the viral accumulation in SBPH, as detected using RT-qPCR and Western blotting. The processing of precursor 7 (POP7), a subunit of RNase P and RNase MRP, was screened, identified, and verified using a dual luciferase reporter assay as one target of miR750-3p. Knockdown of POP7 notably increased RBSDV viral propagation in SBPH and then increased the viral transmission rate by SBPH. Taken together, our data indicate that miR750-3p targets POP7 to suppress RBSDV infection in its insect vector. These results enriched the role of POP7 in modulating virus infection in host insects and shared new insight into the function of miRNAs in plant virus and insect vector interaction.

The miR-184-3p promotes rice black-streaked dwarf virus infection by suppressing Ken in Laodelphax striatellus (Fallén).

MicroRNAs (miRNAs) play a key role in various biological processes by influencing the translation of target messenger RNAs (mRNAs) through post-transcriptional regulation. The miR-184-3p has been identified as an abundant conserved miRNA in insects. However, less is known about its functions in insect-plant virus interactions. The function of miR-184-3p in regulation of plant viral infection in insects was investigated using a rice black-streaked dwarf virus (RBSDV) and Laodelphax striatellus (Fallén) interaction system. We found that the expression of miR-184-3p increased in L. striatellus after RBSDV infection. Injection of miR-184-3p mimics increased RBSDV accumulation, while treatment with miR-184-3p antagomirs inhibits the viral accumulation in L. striatellus. Ken, a zinc finger protein, was identified as a target of miR-184-3p. Knockdown of Ken increased the virus accumulation and promoted RBSDV transmission by L. striatellus. This study demonstrates that RBSDV infection induces the expression of miR-184-3p in its insect vector L. striatellus. The miR-184-3p targets Ken to promote RBSDV accumulation and transmission. These findings provide a new insight into the function of the miRNAs in regulating plant viral infection in its insect vector. © 2023 Society of Chemical Industry.

A Rice Receptor-like Protein Negatively Regulates Rice Resistance to Southern Rice Black-Streaked Dwarf Virus Infection.

Plants rely on various receptor-like proteins and receptor-like kinases to recognize and defend against invading pathogens. However, research on the role of receptor-like proteins in plant antiviral defense, particularly in rice-virus interactions, is limited. In this study, we identified a receptor-like gene, OsBAP1, which was significantly induced upon infection with southern rice black-streaked dwarf virus (SRBSDV) infection. A viral inoculation assay showed that the OsBAP1 knockout mutant exhibited enhanced resistance to SRBSDV infection, indicating that OsBAP1 plays a negatively regulated role in rice resistance to viral infection. Transcriptome analysis revealed that the genes involved in plant-pathogen interactions, plant hormone signal transduction, oxidation-reduction reactions, and protein phosphorylation pathways were significantly enriched in OsBAP1 mutant plants (osbap1-cas). Quantitative real-time PCR (RT-qPCR) analysis further demonstrated that some defense-related genes were significantly induced during SRBSDV infection in osbap1-cas mutants. Our findings provide new insights into the role of receptor-like proteins in plant immune signaling pathways, and demonstrate that OsBAP1 negatively regulates rice resistance to SRBSDV infection.

The JAK-STAT pathway promotes persistent viral infection by activating apoptosis in insect vectors.

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is an evolutionarily conserved signaling pathway that can regulate various biological processes. However, the role of JAK-STAT pathway in the persistent viral infection in insect vectors has rarely been investigated. Here, using a system that comprised two different plant viruses, Rice stripe virus (RSV) and Rice black-streaked dwarf virus (RBSDV), as well as their insect vector small brown planthopper, we elucidated the regulatory mechanism of JAK-STAT pathway in persistent viral infection. Both RSV and RBSDV infection activated the JAK-STAT pathway and promoted the accumulation of suppressor of cytokine signaling 5 (SOCS5), an E3 ubiquitin ligase regulated by the transcription factor STAT5B. Interestingly, the virus-induced SOCS5 directly interacted with the anti-apoptotic B-cell lymphoma-2 (BCL2) to accelerate the BCL2 degradation through the 26S proteasome pathway. As a result, the activation of apoptosis facilitated persistent viral infection in their vector. Furthermore, STAT5B activation promoted virus amplification, whereas STAT5B suppression inhibited apoptosis and reduced virus accumulation. In summary, our results reveal that virus-induced JAK-STAT pathway regulates apoptosis to promote viral infection, and uncover a new regulatory mechanism of the JAK-STAT pathway in the persistent plant virus transmission by arthropod vectors.

Comparative Proteomic Analyses of Susceptible and Resistant Maize Inbred Lines at the Stage of Enations Forming following Infection by Rice Black-Streaked Dwarf Virus.

Rice black-streaked dwarf virus (RBSDV) is the main pathogen causing maize rough dwarf disease (MRDD) in China. Typical enation symptoms along the abaxial leaf veins prevail in RBSDV-infected maize inbred line B73 (susceptible to RBSDV), but not in X178 (resistant to RBSDV). Observation of the microstructures of epidermal cells and cross section of enations from RBSDV-infected maize leaves found that the increase of epidermal cell and phloem cell numbers is associated with enation formation. To identify proteins associated with enation formation and candidate proteins against RBSDV infection, comparative proteomics between B73 and X178 plants were conducted using isobaric tags for relative and absolute quantitation (iTRAQ) with leaf samples at the enation forming stage. The proteomics data showed that 260 and 316 differentially expressed proteins (DEPs) were identified in B73 and X178, respectively. We found that the majority of DEPs are located in the chloroplast and cytoplasm. Moreover, RBSDV infection resulted in dramatic changes of DEPs enriched by the metabolic process, response to stress and the biosynthetic process. Strikingly, a cell number regulator 10 was significantly down-regulated in RBSDV-infected B73 plants. Altogether, these data will provide value information for future studies to analyze molecular events during both enation formation and resistance mechanism to RBSDV infection.

Functional analysis revealed the involvement of ZmABCB15 in resistance to rice black-streaked dwarf virus infection

BackgroundMaize rough dwarf disease (MRDD), caused by rice black-streaked dwarf virus (RBSDV) belonging to the Fijivirus genus, seriously threatens maize production worldwide. Three susceptible varieties (Ye478, Zheng 58, and Zhengdan 958) and two resistant varieties (P138 and Chang7–2) were used in our study.ResultsA set of ATP-binding cassette subfamily B (ABCB) transporter genes were screened to evaluate their possible involvements in RBSDV resistance. In the present study, ZmABCB15, an ABCB transporter family member, was cloned and functionally identified. Expression analysis showed that ZmABCB15 was significantly induced in the resistant varieties, not in the susceptible varieties, suggesting its involvement in resistance to the RBSDV infection. ZmABCB15 gene encodes a putative polar auxin transporter containing two trans-membrane domains and two P-loop nucleotide-binding domains. Transient expression analysis indicated that ZmABCB15 is a cell membrance localized protein. Over-expression of ZmABCB15 enhanced the resistance by repressing the RBSDV replication ratio. ZmABCB15 might participate in the RBSDV resistance by affecting the homeostasis of active and inactive auxins in RBSDV infected seedlings.ConclusionsPolar auxin transport might participate in the RBSDV resistance by affecting the distribution of endogenous auxin among tissues. Our data showed the involvement of polar auxin transport in RBSDV resistance and provided novel mechanism underlying the auxin-mediated disease control technology.

Silencing suppressors of rice black-streaked dwarf virus and rice stripe virus hijack the 26S proteasome of Laodelphax striatellus to facilitate virus accumulation and transmission.

Rice black-streaked dwarf virus (RBSDV) is transmitted by small brown planthopper (Laodelphax striatellus [L. striatellus]) and causes devastating disease in rice. P9-1 has silencing suppression activity and is the key protein for viroplasm formation in RBSDV-infected plants and insects; however, its exact function is poorly understood. In this study, the P9-1 of RBSDV interacted with L. striatellus 26S proteasome subunit RPN8. RBSDV accumulation in L. striatellus increased after the 26S proteasome was disrupted by silencing the RPN8 expression. This finding indicated that L. striatellus 26S proteasome played a defense role against RBSDV infection by regulating RBSDV accumulation. Further investigations revealed that P9-1 could competitively bind to RPN8 with RPN7, thereby disrupting the assembly of 26S proteasome in L. striatellus and promoting the infection of RBSDV in insect vectors, and further affecting the transmission of the virus to rice by insect vectors. Similar to P9-1, rice stripe virus (RSV) NS2, a weak silencing suppressor, regulated virus accumulation and transmission by hijacking RPN8 to interfere with the function of 26S proteasome in L. striatellus. These results suggest that viruses promote their own infection via interfering with ubiquitination pathway of insect vectors, and this mechanism might be of universal importance. These findings provide a new insight into the mechanism of virus transmission in insect vectors. © 2022 Society of Chemical Industry.

Genome‐wide identification and characterization of long noncoding RNAs in maize under rice black streaked dwarf virus infection

AbstractThe functions of long noncoding (lnc) RNA in the response of maize to infection by rice black streaked dwarf virus (RBSDV) is poorly understood, and therefore, a comprehensive disease‐responding lncRNA profile in maize infected with RBSDV was investigated. A total of 38,511 mRNAs and 2717 lncRNAs were identified by performing transcriptomic analysis of maize leaves infected with the virus, including 558 and 8276 differentially expressed lncRNAs (DElncRs) and mRNAs (DEmRs). Functional enrichment analysis of DEmRs showed that multiple immune‐related pathways were significantly enriched (p < 0.05), such as “plant hormone signal transduction”, “phenylpropanoid biosynthesis”, and “plant–pathogen interaction”. There were 248 DElncR‐DEmR pairs, including 169 DElncRs and 236 target DEmRs generated by combining location information and differentially expressed transcripts in this work. In addition, we found that the promoter of lncRNA MSTRG.17772.1 that responds to RBSDV contains abscisic acid (ABA)‐ and methyl jasmonate (MeJA)‐responsive regions, and these two hormones can increase the level of MSTRG.17772.1 and corresponding target mRNA Zm00001d049643_T003, suggesting that ABA and MeJA may respond to RBSDV infection through MSTRG.17772.1–Zm00001d049643_T003 in maize. Our findings revealed the expression of RBSDV‐responsive lncRNAs in maize and provide novel insights into the connection between lncRNAs and ABA and MeJA in the regulation of plant disease resistance.

ATP-binding cassette transporters ABCF2 and ABCG9 regulate rice black-streaked dwarf virus infection in its insect vector, Laodelphax striatellus (Fallén).

The majority of plant viral disease is transmitted and spread by insect vectors in the field. The small brown planthopper, Laodelphax striatellus (Fallén), is the only efficient vector for rice black-streaked dwarf virus (RBSDV), a devastating plant virus that infects multiple grain crops, including rice, maize, and wheat. Adenosine triphosphate (ATP)-binding cassette (ABC) transporters participate in various biological processes. However, little is known about whether ABC transporters affect virus infection in insects. In this study, RBSDV accumulation was significantly reduced in L. striatellus after treatment with verapamil, an effective inhibitor of ABC transporters. Thirty-four ABC transporter genes were identified in L. striatellus and expression analysis showed that LsABCF2 and LsABCG9 were significantly upregulated and downregulated, respectively, after RBSDV infection. LsABCF2 and LsABCG9 were expressed during all developmental stages, and LsABCG9 was highly expressed in the midgut of L. striatellus. Knockdown of LsABCF2 promoted RBSDV accumulation, while knockdown of LsABCG9 suppressed RBSDV accumulation in L. striatellus. Our data showed that L. striatellus might upregulate the expression of LsABCF2 and downregulate LsABCG9 expression to suppress RBSDV infection. These results will contribute to understanding the effects of ABC transporters on virus transmission and provide theoretical basis for virus management in the field.

Cytochrome P450 Monooxygenases CYP6AY3 and CYP6CW1 Regulate Rice Black-Streaked Dwarf Virus Replication in Laodelphax striatellus (Fallén).

The small brown planthopper, Laodelphax striatellus (Fallén), is an important agricultural pest that causes significant losses by sucking and transmitting multiple plant viruses, such as rice black-streaked dwarf virus (RBSDV). Insecticides are commonly used to control planthoppers and cause the induction or overexpression of cytochrome P450 monooxygenases (P450s) from the CYP3 and CYP4 clades after insecticide application. However, little is known about the roles of insecticides and P450s in the regulation of viral replication in insects. In this study, RBSDV-infected L. striatellus were injected with imidacloprid, deltamethrin, pymetrozine, and buprofezin, respectively. The insecticide treatments caused a significant decrease in RBSDV abundance in L. striatellus. Treatment of piperonyl butoxide (PBO), an effective inhibitor of P450s, significantly increased the RBSDV abundance in L. striatellus. Fourteen P450 candidate genes in the CYP3 clade and 21 in the CYP4 clade were systematically identified in L. striatellus, and their expression patterns were analyzed under RBSDV infection, in different tissues, and at different developmental stages. Among the thirty-five P450 genes, the expression level of CYP6CW1 was the highest, while CYP6AY3 was the lowest after RBSDV infection. Knockdown of CYP6CW1 and CYP6AY3 significantly increased the virus abundance and promoted virus replication in L. striatellus. Overall, our data reveal that CYP6CW1 and CYP6AY3 play a critical role in the regulation of virus replication in L. striatellus.

Rice black-streaked dwarf virus P10 promotes phosphorylation of GAPDH (glyceraldehyde-3-phosphate dehydrogenase) to induce autophagy in Laodelphax striatellus

ABSTRACT Macroautophagy/autophagy is an important innate and adaptive immune response that can clear microbial pathogens through guiding their degradation. Virus infection in animals and plants is also known to induce autophagy. However, how virus infection induces autophagy is largely unknown. Here, we provide evidence that the early phase of rice black-streaked dwarf virus (RBSDV) infection in Laodelphax striatellus can also induce autophagy, leading to suppression of RBSDV invasion and accumulation. We have determined that the main capsid protein of RBSDV (P10) is the inducer of autophagy. RBSDV P10 can specifically interact with GAPDH (glyceraldehyde-3-phosphate dehydrogenase), both in vitro and in vivo. Silencing of GAPDH in L. striatellus could significantly reduce the activity of autophagy induced by RBSDV infection. Furthermore, our results also showed that both RBSDV infection and RBSDV P10 alone can promote phosphorylation of AMP-activated protein kinase (AMPK), resulting in GAPDH phosphorylation and relocation of GAPDH from the cytoplasm into the nucleus in midgut cells of L. striatellus or Sf9 insect cells. Once inside the nucleus, phosphorylated GAPDH can activate autophagy to suppress virus infection. Together, these data illuminate the mechanism by which RBSDV induces autophagy in L. striatellus, and indicate that the autophagy pathway in an insect vector participates in the anti-RBSDV innate immune response. Abbreviations3-MA: 3-methyladenine; AMPK: AMP-activated protein kinase; ATG: autophagy-related; co-IP: co-immunoprecipitation; DAPI: 4ʹ,6-diamidino-2-phenylindole; dpf: days post-feeding; dsRNA: double-stranded RNA; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GST: glutathione-S-transferase; RBSDV: Rice black-streaked dwarf virus; TEM: transmission electron microscope.

ARGONAUTE 2 increases rice susceptibility to rice black-streaked dwarf virus infection by epigenetically regulating HEXOKINASE 1 expression.

ARGONAUTE (AGO) proteins play crucial roles in plant defence against virus invasion. To date, the role of OsAGO2 in rice antiviral defence remains largely unknown. In this study, we determined that the expression of OsAGO2 in rice was induced upon rice black‐streaked dwarf virus (RBSDV) infection. Using transgenic rice plants overexpressing OsAGO2 and Osago2 mutants generated through transposon‐insertion or CRISPR/Cas9 technology, we found that overexpression of OsAGO2 enhanced rice susceptibility to RBSDV infection. Osago2 mutant lines exhibited strong resistance to RBSDV infection through the elicitation of an early defence response, including reprogramming defence gene expression and production of reactive oxygen species (ROS). Compared to Nipponbare control, the expression level of OsHXK1 (HEXOKINASE 1) increased significantly, and the methylation levels of its promoter decreased in the Osago2 mutant on RBSDV infection. The expression profile of OsHXK1 was the opposite to that of OsAGO2 during RBSDV infection. Overexpression of OsHXK1 in rice also induced ROS production and enhanced rice resistance to RBSDV infection. These results indicate that OsHXK1 controls ROS accumulation and is regulated by OsAGO2 through epigenetic regulation. It is noteworthy that the Osago2 mutant plants are also resistant to southern rice black‐streaked dwarf virus infection, another member of the genus Fijivirus. Based on the results presented in this paper, we conclude that OsAGO2 modulates rice susceptibility to fijivirus infection by suppressing OsHXK1 expression, leading to the onset of ROS‐mediated resistance. This discovery may benefit future rice breeding programmes for virus resistance.

MicroRNA-315-5p promotes rice black-streaked dwarf virus infection by targeting a melatonin receptor in the small brown planthopper.

MicroRNAs (miRNAs), a class of small non-coding endogenous RNAs, play key roles in various biological processes. Most plant viruses are transmitted by insect vectors. However, little is known about the function of miRNAs on plant virus-insect host interaction. We investigated the role of miR-315-5p in regulation of plant viral infection in insects using a rice black-streaked dwarf virus (RBSDV) and small brown planthopper (SBPH) interaction system. Our results showed that miR-315-5p had the highest expression level in 2nd-instar nymph, and was highly expressed in the salivary gland and midgut in SBPH. miR-315-5p was in response to and regulated RBSDV infection in SBPH. Injection of miR-315-5p mimic, agomir-315, significantly increased the RBSDV accumulation, whereas injection of miR-315-5p inhibitor, antagomir-315, reduced virus accumulation in SBPH. Furthermore, a melatonin receptor was identified as a target gene of miR-315-5p by the dual luciferase reporter assay. Knockdown of the melatonin receptor significantly increased the expression of RBSDV coat protein gene S10 and replication related genes, S5-1, S6, and S9-1. Furthermore, treatment with melatonin receptor antagonist luzindole and activator agomelatine significantly increased and reduced RBSDV accumulation in SBPH, respectively. Compared to the control, miR-315-5p did not affect the efficiency of RBSDV acquisition in SBPH. However, the efficiency of RBSDV transmission was significantly reduced after injecting antagomir-315. Taken together, our data reveal that miR-315-5p is beneficial for RBSDV infection in its insect vector by directly targeting a melatonin receptor. These findings provide a new insight to the function of miRNAs in virus-insect vector interaction. © 2021 Society of Chemical Industry.

Maize AKINβγ Proteins Interact with P8 of Rice Black Streaked Dwarf Virus and Inhibit Viral Infection.

Rice black streaked dwarf virus (RBSDV) is an important agent causing maize rough dwarf disease, whereas the host factors responding to RBSDV infection are poorly understood. To uncover the molecular interactions between RBSDV and maize, a yeast two-hybrid screen of a maize cDNA library was carried out using the viral P8 protein as a bait. ZmAKINβγ-1 and ZmAKINβγ-2 (βγ subunit of Arabidopsis SNF1 kinase homolog in maize) possessing high sequence similarities (encoded by two gene copies) were identified as interaction partners. Their interactions with P8 were confirmed in both Nicotiana benthamiana cells and maize protoplasts by bimolecular fluorescence complementation assay. The accumulation levels of ZmAKINβγ mRNAs were upregulated at the stage of the viral symptoms beginning to appear and then downregulated. ZmAKINβγs are putative regulatory subunits of the SnRK1 complex, a core regulator for energy homeostasis. Knockdown of ZmAKINβγs in maize regulated the expression levels of the genes involved in sugar synthesis or degradation, and also the contents of both glucose and sucrose. Importantly, downregulation of ZmAKINβγs expressions facilitated the accumulation of RBSDV in maize. These results implicate a role of ZmAKINβγs in the regulation of primary carbohydrate metabolism, and in the defense against RBSDV infection.

Systematic Identification and Functional Analysis of Circular RNAs During Rice Black-Streaked Dwarf Virus Infection in the Laodelphax striatellus (Fallén) Midgut.

Circular RNAs (circRNAs) are endogenous RNAs that have critical regulatory roles in numerous biological processes. However, it remains largely unknown whether circRNAs are induced in response to plant virus infection in the insect vector of the virus as well as whether the circRNAs regulate virus infection. Rice black-streaked dwarf virus (RBSDV) is transmitted by Laodelphax striatellus (Fallén) in a persistent propagative manner and causes severe losses in East Asian countries. To explore the expression and function of circRNAs in the regulation of virus infection, we determined the circRNA expression profile in RBSDV-free or RBSDV-infected L. striatellus midgut tissues by RNA-Seq. A total of 2,523 circRNAs were identified, of which thirteen circRNAs were differentially expressed after RBSDV infection. The functions of these differentially circRNAs were predicted by GO and KEGG pathway analyses. The expression changes of five differentially expressed circRNAs and eight parental genes were validated by RT-qPCR. The circRNAs-microRNAs (miRNAs) interaction networks were analyzed and two miRNAs, which were predicted to bind circRNAs, were differentially expressed after virus infection. CircRNA2030 was up-regulated after RBSDV infection in L. striatellus midgut. Knockdown of circRNA2030 by RNA interference inhibited the expression of its predicted parental gene phospholipid-transporting ATPase (PTA) and enhanced RBSDV infection in L. striatellus. However, none of the six miRNAs predicting to bind circRNA2030 was up-regulated after circRNA2030 knockdown. The results suggested that circRNA2030 might affect RBSDV infection via regulating PTA. Our results reveal the expression profile of circRNAs in L. striatellus midgut and provide new insight into the roles of circRNAs in virus–insect vector interaction.

Transcriptome Analysis of Rice Reveals the lncRNA-mRNA Regulatory Network in Response to Rice Black-Streaked Dwarf Virus Infection.

The plant genome can produce long non-coding RNAs (lncRNAs), some of which have been identified as important regulators of gene expression. To better understand the response mechanism of rice plants to Rice black-streaked dwarf virus (RBSDV) infection, we performed a comparative transcriptome analysis between the RBSDV-infected and non-infected rice plants. A total of 1342 mRNAs and 22 lncRNAs were identified to be differentially expressed after RBSDV infection. Most differentially expressed transcripts involved in the plant–pathogen interaction pathway were upregulated after RBSDV infection, indicating the activation of rice defense response by RBSDV. A network of differentially expressed lncRNAs (DElncRNAs) and mRNAs (DEmRNAs) was then constructed. In this network, there are 56 plant–pathogen interaction-related DEmRNAs co-expressing with 20 DElncRNAs, suggesting these DElncRNAs and DEmRNAs may play essential roles in rice innate immunity against RBSDV. Moreover, some of the lncRNA–mRNA regulatory relationships were experimentally verified in rice calli by a quick and effective method established in this study. Three DElncRNAs were selected to be tested, and the results indicated that five mRNAs were found to be regulated by them. Together, we give a whole landscape of rice mRNAs and lncRNAs in response to RBSDV infection, and a feasible method to rapidly verify the lncRNA–mRNA regulatory relationship in rice.

Comprehensive Identification and Characterization of Long Non-coding RNAs Associated With Rice Black-Streaked Dwarf Virus Infection in Laodelphax striatellus (Fallén) Midgut

Long non-coding RNAs (lncRNAs) are involved in a variety of biological functions through transcriptional and post-transcriptional regulation. However, little is known about their functions in the process of insect mediated virus transmission. In the present study, we analyzed using RNA-Seq, the lncRNAs that were differentially expressed in response to Rice black-streaked dwarf virus (RBSDV) infection in Laodelphax striatellus (Fallén) midgut. A total of 13,927 lncRNAs were identified and over 69% were assigned to intergenic regions. Among them, 176 lncRNAs were differentially expressed and predicted to target 168 trans-regulatory genes. Ten differentially expressed lncRNAs were selected and their expression changes were validated by RT-qPCR. KEGG analysis showed that these target genes were enriched in the essential biological process, such as Purine metabolism, Valine, leucine and isoleucine degradation, and Fatty acid elongation. The expression levels of the differentially expressed lncRNAs and the predicted target genes that were significantly enriched in the Human papillomavirus infection pathway were analyzed by RT-qPCR. The results showed that several lncRNAs were co-expressed with their target genes. One of the lncRNAs called MSTRG15394 and its target gene, encoding a secreted protease inhibitor (PI), were up-regulated at the transcriptional level after RBSDV infection. Knockdown of MSTRG15394 could down-regulate the PI expression at mRNA level. Inhibition of either MSTRG15394 or PI expression by RNA interference promoted RBSDV accumulation in L. striatellus midgut. Our finding provides new insights into the function of lncRNAs in regulating virus infection in an important insect vector.

Rice black-streaked dwarf virus-encoded P5-1 regulates the ubiquitination activity of SCF E3 ligases and inhibits jasmonate signaling to benefit its infection in rice.

Summary SCF (Skp1/Cullin1/F‐box) complexes are key regulators of many cellular processes. Viruses encode specific factors to interfere with or hijack these complexes and ensure their infection in plants. The molecular mechanisms controlling this interference/hijack are currently largely unknown.Here, we present evidence of a novel strategy used by Rice black‐streaked dwarf virus (RBSDV) to regulate ubiquitination in rice (Oryza sativa) by interfering in the activity of OsCSN5A. We also show that RBSDV P5‐1 specifically affects CSN‐mediated deRUBylation of OsCUL1, compromising the integrity of the SCFCOI1 complex.We demonstrate that the expressions of jasmonate (JA) biosynthesis‐associated genes are not inhibited, whereas the expressions of JA‐responsive genes are down‐regulated in transgenic P5‐1 plants. More importantly, application of JA to P5‐1 transgenic plants did not reduce their susceptibility to RBSDV infection.Our results suggest that P5‐1 inhibits the ubiquitination activity of SCF E3 ligases through an interaction with OsCSN5A, and hinders the RUBylation/deRUBylation of CUL1, leading to an inhibition of the JA response pathway and an enhancement of RBSDV infection in rice.

The Dual Effect of the Brassinosteroid Pathway on Rice Black-Streaked Dwarf Virus Infection by Modulating the Peroxidase-Mediated Oxidative Burst and Plant Defense.

The phytohormone brassinosteroid (BR) not only plays key roles in regulating plant growth and development but is also involved in modulating the plant defense system in response to pathogens. We previously found that BR application made rice plants more susceptible to the devastating pathogen rice black-streaked dwarf virus (RBSDV), but the mechanism of BR-mediated susceptibility remains unclear. We now show that both BR-deficient and -insensitive mutants are resistant to RBSDV infection. High-throughput sequencing showed that the defense hormone salicylic acid and jasmonic acid pathways were activated in the RBSDV-infected BR mutant. Meanwhile, a number of class III peroxidases (OsPrx) were significantly changed and basal reactive oxygen species (ROS) accumulated in BR mutants. Treatment with exogenous hormones and other chemicals demonstrated that the BR pathway could suppress the levels of OsPrx and the ROS burst by directly binding the promoters of OsPrx genes. Together, our findings indicate that BR-mediated susceptibility is at least partly caused by inhibition of the action of defense hormones, preventing the accumulation of the peroxidase-mediated oxidative burst.