Variable eIF4E-binding sites and their synergistic effect on cap-independent translation in a novel IRES of wheat yellow mosaic virus RNA2 isolates.

Some viral proteins are translated cap-independently via the internal ribosome entry site (IRES), which maintains conservative characteristic among different isolates of the same virus species. However, IRES activity showed a 7-fold variance in RNA2 of wheat yellow mosaic virus (WYMV) HC and LYJN isolates in this study. Based on RNA structure probing and mutagenesis assay, the loosened middle stem of H1 and the hepta-nucleotide top loop of H2 in the LYJN isolate synergistically ensured higher IRES activity than that in the HC isolate. In addition, the conserved top loop of H1 ensured basic IRES activity in HC and LYJN isolates. WYMV RNA2 5'-UTR specifically interacted with the wheat eIF4E, accomplished by the top loop of H1 in the HC isolate or the top loop of H1 and H2 in the LYJN isolate. The high IRES activity of the WYMV RNA2 LYJN isolate was regulated by two eIF4E-binding sites, which showed a synergistic effect mediated by the proximity of the H1 and H2 top loops owing to the flexibility of the middle stem in H1. This report presents a novel evolution pattern of IRES, which altered the number of eIF4E-binding sites to regulate IRES activity.

Detection and characterization of a putative emaravirus infecting Clematis brevicaudata DC. in China.

A novel emaravirus, tentatively named "clematis yellow mottle associated virus" (CYMaV), was identified through transcriptome sequencing and RT-PCR analysis of yellow-mottled leaf samples from Clematis brevicaudata DC. The genome of CYMaV consists of five viral RNAs: RNA1 (6591 nucleotides, nt), RNA2 (1982 nt), RNA3a (1301 nt), RNA3b (1397 nt), and RNA4 (1192 nt). The 13-nt sequences at the 5'- and 3'-termini of the CYMaV RNAs are conserved and have reverse complementary, as typically seen in emaraviruses. The proteins encoded by CYMaV shared the highest amino acid sequence similarity with those of the unclassified Karaka Okahu purepure emaravirus (KOPV), with 60.2% identity in the RNA-dependent RNA polymerase (RdRp), 44.4% in the glycoprotein precursor, and 46.9% in the nucleocapsid protein. A phylogenetic tree based on amino acid sequences of the RdRp revealed that CYMaV is most closely related to KOPV and clusters with ChMaV (chrysanthemum mosaic-associated virus, LC576445) and PCLSaV (pear chlorotic leaf spot-associated virus, MK602177) in one distinct clade. Transmission electron microscopy observation of negatively stained samples from C. brevicaudata revealed spherical virus-like particles (VLPs) approximately 100 nm in diameter. Five primers, specific for each viral RNA, were used to detect CYMaV in 11 symptomatic and two asymptomatic C. brevicaudata samples, but the results failed to show a consistent association of viral infection with symptoms. CYMaV can be considered a putative new member in the genus Emaravirus, and this marks the first report of an emaravirus found infecting C. brevicaudata plants.

A papain-like cysteine protease-released small signal peptide confers wheat resistance to wheat yellow mosaic virus.

Wheat yellow mosaic virus (WYMV), a soil-borne pathogen, poses a serious threat to global wheat production. Here, we identify a WYMV resistance gene, TaRD21A, that belongs to the papain-like cysteine protease family. Through genetic manipulation of TaRD21A expression, we establish its positive role in the regulation of wheat to WYMV resistance. Furthermore, our investigation shows that the TaRD21A-mediated plant antiviral response relies on the release of a small peptide catalyzed by TaRD21A protease activity. To counteract wheat resistance, WYMV-encoded nuclear inclusion protease-a (NIa) suppress TaRD21A activity to promote virus infection. In resistant cultivars, a natural variant of TaRD21A features a glycine-to-threonine substitution and this substitution enables the phosphorylation of threonine, thereby weakening the interaction between NIa and TaRD21A, reinforcing wheat resistance against WYMV. Our study not only unveils a WYMV resistance gene but also offers insights into the intricate mechanisms underpinning resistance against WYMV.

Molecular identification and development of an infectious cDNA clone of Trichosanthes kirilowii-infecting cucurbit mild mosaic virus.

Trichosanthes kirilowii has been mainly grown for use in traditional Chinese medicine. In this study, cucurbit mild mosaic virus (CuMMV) belonging to the genus Fabavirus was identified from T. kirilowii plants. CuMMV possesses a segmented, bipartite linear single-stranded RNA genome composed of RNA1 and RNA2. Sequence analysis showed that each genomic segment shares the highest sequence similarity with those of CuMMV isolated from pumpkin. A full-length infectious cDNA clone of CuMMV was further constructed and was found to induce typical symptoms in T. kirilowii, Cucumis sativus, C. melo, Citrullus lanatus, and Cucurbita pepo. The sap inoculum derived from the infectious cDNA clone of CuMMV could be mechanically transmitted and reproduce similar symptoms in the tested plants. This is the first report on the construction of a biologically active, full-length infectious cDNA clone of CuMMV, which will provide a useful tool in understanding CuMMV-encoded proteins and plant-CuMMV interactions.

Specific Nucleotides in the Common Region of the Begomovirus Tomato Rugose Mosaic Virus (ToRMV) Are Responsible for the Negative Interference over Tomato Severe Rugose Virus (ToSRV) in Mixed Infection.

Mixed infection between two or more begomoviruses is commonly found in tomato fields and can affect disease outcomes by increasing symptom severity and viral accumulation compared with single infection. Viruses that affect tomato include tomato severe rugose virus (ToSRV) and tomato rugose mosaic virus (ToRMV). Previous work showed that in mixed infection, ToRMV negatively affects the infectivity and accumulation of ToSRV. ToSRV and ToRMV share a high degree of sequence identity, including cis-elements in the common region (CR) and their specific recognition sites (iteron-related domain, IRD) within the Rep gene. Here, we investigated if divergent sites in the CR and IRD are involved in the interaction between these two begomoviruses. ToSRV clones were constructed containing the same nucleotides as ToRMV in the CR (ToSRV-A(ToR:CR)), IRD (ToSRV-A(ToR:IRD)) and in both regions (ToSRV-A(ToR:CR+IRD)). When plants were co-inoculated with ToRMV and ToSRV-A(ToR:IRD), the infectivity and accumulation of ToSRV were negatively affected. In mixed inoculation of ToRMV with ToSRV-A(ToR:CR), high infectivity of both viruses and high DNA accumulation of ToSRV-A(ToR:CR) were observed. A decrease in viral accumulation was observed in plants inoculated with ToSRV-A(ToR:CR+IRD). These results indicate that differences in the CR, but not the IRD, are responsible for the negative interference of ToRMV on ToSRV.

The P1 protein of wheat yellow mosaic virus exerts RNA silencing suppression activity to facilitate virus infection in wheat plants.

Wheat yellow mosaic virus (WYMV) causes severe wheat viral disease in Asia. However, the viral suppressor of RNA silencing (VSR) encoded by WYMV has not been identified. Here, the P1 protein encoded by WYMV RNA2 was shown to suppress RNA silencing in Nicotiana benthamiana. Mutagenesis assays revealed that the alanine substitution mutant G175A of P1 abolished VSR activity and mutant Y10A VSR activity remained only in younger leaves. P1, but not G175A, interacted with gene silencing-related protein, N. benthamiana calmodulin-like protein (NbCaM), and calmodulin-binding transcription activator 3 (NbCAMTA3), and Y10A interacted with NbCAMTA3 only. Competitive Bimolecular fluorescence complementation and co-immunoprecipitation assays showed that the ability of P1 disturbing the interaction between NbCaM and NbCAMTA3 was stronger than Y10A, Y10A was stronger than G175A. In vitro transcript inoculation of infectious WYMV clones further demonstrated that VSR-defective mutants G175A and Y10A reduced WYMV infection in wheat (Triticum aestivum L.), G175A had a more significant effect on virus accumulation in upper leaves of wheat than Y10A. Moreover, RNA silencing, temperature, and autophagy have significant effects on the accumulation of P1 in N. benthamiana. Taken together, WYMV P1 acts as VSR by interfering with calmodulin-associated antiviral RNAi defense to facilitate virus infection in wheat, which has provided clear insights into the function of P1 in the process of WYMV infection.

Chloroplast-related host proteins interact with NIb and NIa-Pro of soybeans mosaic virus and induce resistance in the susceptible cultivar.

To gain a deeper understanding of the molecular mechanisms involved in viral infection and the corresponding plant resistance responses, it is essential to investigate the interactions between viral and host proteins. In the case of viral infections in plants, a significant portion of the affected gene products are closely associated with chloroplasts and photosynthesis. However, the molecular mechanisms underlying the interplay between the virus and host chloroplast proteins during replication remain poorly understood. In our previous study, we made an interesting discovery regarding soybean mosaic virus (SMV) infection in resistant and susceptible soybean cultivars. We found that the photosystem I (PSI) subunit (PSaC) and ATP synthase subunit α (ATPsyn-α) genes were up-regulated in the resistant cultivar following SMV-G7H and SMV-G5H infections compared to the susceptible cultivar. Overexpression of these two genes within the SMV-G7H genome in the susceptible cultivar Lee74 (rsv3-null) reduced SMV accumulation, whereas silencing of the PSaC and ATPsyn-α genes promoted SMV accumulation. We have also found that the PSaC and ATPsyn-α proteins are present in the chloroplast envelope, nucleus, and cytoplasm. Building on these findings, we now characterized protein-protein interactions between PSaC and ATPsyn-α with two viral proteins, NIb and NIa-Pro, respectively, of SMV. Through co-immunoprecipitation (Co-IP) experiments, we confirmed the interactions between these proteins. Moreover, when the C-terminal region of either PSaC or ATPsyn-α was overexpressed in the SMV-G7H genome, we observed a reduction in viral accumulation and systemic infection in the susceptible cultivar. Based on these results, we propose that the PSaC and ATPsyn-α genes play a modulatory role in conferring resistance to SMV infection by influencing the function of NIb and NIa-Pro-in SMV replication and movement. The identification of these photosynthesis-related genes as key players in the interplay between the virus and the host provides valuable insights for developing more targeted control strategies against SMV. Additionally, by utilizing these genes, it may be possible to genetically engineer plants with improved photosynthetic efficiency and enhanced resistance to SMV infection.

Complete genome sequence of zoysia mosaic virus, a novel member of the genus Poacevirus.

Here, we report the detection and characterization of the genome of a novel poacevirus isolated from Zoysia matrella (Merrill) imported into the United States from Japan. The novel virus, tentatively named "zoysia mosaic virus" (ZoMV), is a single-stranded RNA virus with a genome of 9,728 nucleotides (nt) in length, encoding a large putative polyprotein of 3,119 amino acids (aa). The ZoMV genome is closely related to the triticum mosaic virus (TriMV; FJ263671) genome, with 57.18% nt and 51.74% aa sequence identity in the polyprotein region. Moreover, phylogenetic analysis showed that ZoMV is closely related to all other members of the genus Poacevirus. A survey of imported grasses showed that ZoMV was detected only in zoysiagrass. This is the first report of the complete genome sequence of a novel viral pathogen of zoysiagrass of the genus Poacevirus, for which we propose the binomial species name "Poacevirus zoisiae".

Cajanus Scarabaeoides Yellow Mosaic Virus, a New Bipartite Begomovirus Causing Yellow Mosaic Disease in Cajanus scarabaeoides in India.

Yellow mosaic disease of Cajanus scarabaeoides (L.) Thouars (CsYMD) was observed in up to 46% of C. scarabaeoides plants in the mungbean, urdbean, and pigeon pea fields from 22 districts of Chhattisgarh State, India, during 2017 to 2019. The symptoms were characterized by yellow mosaic on green leaves and yellow discoloration of leaves in advanced stages of the disease. Severely infected plants showed shortened internodal length and reduced leaf size. CsYMD was transmissible to healthy C. scarabaeoides and C. cajan by whitefly (Bemisia tabaci). The infected plants developed typical yellow mosaic symptoms on their leaves within 16 and 22 days of inoculation, respectively, suggesting a begomovirus etiology. Molecular analysis revealed that this begomovirus has a bipartite genome composed of DNA-A (2,729 nucleotides) and DNA-B (2,630 nucleotides). Sequence and phylogenetic analyses revealed that the nucleotide sequence of the DNA-A component had the highest identity of 81.1% with DNA-A of Rhynchosia yellow mosaic virus (RhYMV; NC_038885), followed by mungbean yellow mosaic virus (MN602427; 75.3%). DNA-B had the highest identity of 74.0% with DNA-B of RhYMV (NC_038886). As per ICTV guidelines, this isolate had <91% nucleotide identity with DNA-A of any of the begomoviruses reported; so, it is proposed as a new begomovirus species, tentatively named C. scarabaeoides yellow mosaic virus (CsYMV). After agroinoculation with DNA-A and DNA-B clones of CsYMV, all Nicotiana benthamiana plants developed leaf curl symptoms along with light yellowing symptoms 8 to 10 days after inoculation (DAI), while ∼60% of the C. scarabaeoides plants developed yellow mosaic symptoms similar to those observed in the field 18 DAI, thus fulfilling Koch's postulates. From these agro-infected C. scarabaeoides plants, CsYMV was transmissible to healthy C. scarabaeoides plants by B. tabaci. Apart from these hosts, CsYMV also infected and caused symptoms in mungbean and pigeon pea.

Genomic characterization of a novel torradovirus infecting Arctium lappa L. in China.

Burdock (Arctium lappa L.) is not only a popular vegetable crop but also an important medicinal plant. In burdock plants with symptoms of leaf mosaic, a novel torradovirus tentatively named "burdock mosaic virus" (BdMV) was identified by high-throughput sequencing. The complete genomic sequence of BdMV was further determined using RT-PCR and the rapid amplification of cDNA ends (RACE) method. The genome is composed of two positive-sense single-stranded RNAs. RNA1 (6991 nt) encodes a polyprotein of 2186 aa, and RNA2 (4700 nt) encodes a protein of 201 aa and a polyprotein of 1212 aa that is predicted to be processed into one movement protein (MP) and three coat proteins (CPs). The Pro-Pol region of RNA1 and the CP region of RNA2 shared the highest amino acid sequence identity of 74.0% and 70.6%, respectively, with the corresponding sequences of lettuce necrotic leaf curl virus (LNLCV) isolate JG3. Phylogenetic analysis based on the amino acid sequences of the Pro-Pol and CP regions showed that BdMV clustered with other non-tomato-infecting torradoviruses. Taken together, these results suggest that BdMV is a new member of the genus Torradovirus.

Complete genome sequence of mimosa mosaic virus, a new sobemovirus infecting Mimosa sensitiva L.

A new sobemovirus, which we have named "mimosa mosaic virus" (MimMV), was found by high-throughput sequencing and isolated from a mimosa (Mimosa sensitiva L.) plant. The genome sequence was confirmed by Sanger sequencing and comprises 4595 nucleotides. Phylogenetic analysis based on the predicted amino acid (aa) sequences of the P2b protein (encoded by ORF2b) and the coat protein showed 52.7% and 31.8% aa sequence identity, respectively, to those of blueberry shoestring virus. The complete genome sequence of MimMV was less than 47% identical to those of other sobemoviruses. These data suggest that MimMV is a member of a new species in the genus Sobemovirus, for which the binomial name "Sobemovirus mimosae" is proposed.

Wheat yellow mosaic virus NIb targets TaVTC2 to elicit broad-spectrum pathogen resistance in wheat.

GDP-L-galactose phosphorylase (VTC2) catalyses the conversion of GDP-L-galactose to L-galactose-1-P, a vital step of ascorbic acid (AsA) biosynthesis in plants. AsA is well known for its function in the amelioration of oxidative stress caused by most pathogen infection, but its function against viral infection remains unclear. Here, we have identified a VTC2 gene in wheat named as TaVTC2 and investigated its function in association with the wheat yellow mosaic virus (WYMV) infection. Our results showed that overexpression of TaVTC2 significantly increased viral accumulation, whereas knocking down TaVTC2 inhibited the viral infection in wheat, suggesting a positive regulation on viral infection by TaVTC2. Moreover, less AsA was produced in TaVTC2 knocking down plants (TaVTC2-RNAi) which due to the reduction in TaVTC2 expression and subsequently in TaVTC2 activity, resulting in a reactive oxygen species (ROS) burst in leaves. Furthermore, the enhanced WYMV resistance in TaVTC2-RNAi plants was diminished by exogenously applied AsA. We further demonstrated that WYMV NIb directly bound to TaVTC2 and inhibited TaVTC2 enzymatic activity in vitro. The effect of TaVTC2 on ROS scavenge was suppressed by NIb in a dosage-dependent manner, indicating the ROS scavenging was highly regulated by the interaction of TaVTC2 with NIb. Furthermore, TaVTC2 RNAi plants conferred broad-spectrum disease resistance. Therefore, the data indicate that TaVTC2 recruits WYMV NIb to down-regulate its own enzymatic activity, reducing AsA accumulation to elicit a burst of ROS which confers the resistance to WYMV infection. Thus, a new mechanism of the formation of plant innate immunity was proposed.

Construction of Full-Length Infectious cDNA Clones of Citrus Mosaic Virus RNA1 and RNA2 and Infection of Citrus Seedlings by Agrobacterium-Mediated Vacuum-Infiltration.

The development of full-length infectious cDNA clones for plant RNA viruses is important for studying their molecular biological characteristics, functional genomics, pathogenesis, and vectorization applications. Citrus mosaic virus (CiMV), a member of the genus Sadwavirus, is of economic importance to the citrus industry and comprises a bipartite, positive-sense, single-stranded RNA genome encapsidated in icosahedral virions. In the present study, full-length cDNA clones of CiMV RNA1 and RNA2 were constructed based on a ternary yeast-Escherichia coli-Agrobacterium tumefaciens shuttle vector, pTY, using transformation-associated recombination (TAR) strategy. Infectivity of cDNA clones of CiMV RNA1 and RNA2 was examined in multiple citrus varieties via Agrobacterium-mediated vacuum-infiltration (AVI) through symptom observation, RT-PCR, and virion detection with an electron microscope. Furthermore, the genome-sized RT-PCR fragments of RNA1 and RNA2 were obtained from symptomatic Jinchengyou (Citrus grandis) plants infected by the cloned virus (CiMV211). In addition, CiMV211 produced typical symptoms of wild-type CiMV in cowpea (Vigna angularis) plants inoculated by Agrobacterium-mediated injection. This is the first report of infectious cDNA clones of CiMV, which may lay the foundation for research on the pathogenesis and vectorization of the virus.

Transcriptome Analysis Reveals a Comprehensive Virus Resistance Response Mechanism in Pecan Infected by a Novel Badnavirus Pecan Virus.

Pecan leaf-variegated plant, which was infected with a novel badnavirus named pecan mosaic virus (PMV) detected by small RNA deep sequencing, is a vital model plant for studying the molecular mechanism of retaining green or chlorosis of virus-infected leaves. In this report, PMV infection in pecan leaves induced PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). PMV infection suppressed the expressions of key genes of fatty acid, oleic acid (C18:1), and very-long-chain fatty acids (VLCFA) biosynthesis, indicating that fatty acids-derived signaling was one of the important defense pathways in response to PMV infection in pecan. PMV infection in pecans enhanced the expressions of pathogenesis-related protein 1 (PR1). However, the transcripts of phenylalanine ammonia-lyase (PAL) and isochorismate synthase (ICS) were downregulated, indicating that salicylic acid (SA) biosynthesis was blocked in pecan infected with PMV. Meanwhile, disruption of auxin signaling affected the activation of the jasmonic acid (JA) pathway. Thus, C18:1 and JA signals are involved in response to PMV infection in pecan. In PMV-infected yellow leaves, damaged chloroplast structure and activation of mitogen-activated protein kinase 3 (MPK3) inhibited photosynthesis. Cytokinin and SA biosynthesis was blocked, leading to plants losing immune responses and systemic acquired resistance (SAR). The repression of photosynthesis and the induction of sink metabolism in the infected tissue led to dramatic changes in carbohydrate partitioning. On the contrary, the green leaves of PMV infection in pecan plants had whole cell tissue structure and chloroplast clustering, establishing a strong antiviral immunity system. Cytokinin biosynthesis and signaling transductions were remarkably strengthened, activating plant immune responses. Meanwhile, cytokinin accumulation in green leaves induced partial SA biosynthesis and gained comparatively higher SAR compared to that of yellow leaves. Disturbance of the ribosome biogenesis might enhance the resistance to PMV infection in pecan and lead to leaves staying green.

Complete genome sequence of Edgeworthia chrysantha mosaic-associated virus, a tentative new member of the genus Coguvirus (family Phenuiviridae).

A new negative-strand RNA (nsRNA) virus genome was discovered in Edgeworthia chrysantha Lindl. This virus, tentatively named "Edgeworthia chrysantha mosaic-associated virus" (ECMaV), has a bipartite genome that comprises (i) a nsRNA1, encoding the viral RNA-dependent RNA polymerase (RdRp), and (ii) an ambisense RNA2, coding for the putative movement protein (MP) and nucleocapsid protein (NP), with the open reading frames separated by a long AU-rich intergenic region (IR). Sequence comparisons and phylogenetic analysis showed that the RdRp is closely related to those of other recently discovered plant-infecting nsRNA viruses in the new genus Coguvirus and that ECMaV can be classified as a member of a novel species.

Genomic characterization of soybean blotchy mosaic virus, a cytorhabdovirus from South Africa.

Samples showing blotchy mottle symptoms were collected from soybeans in North-West province, South Africa. The assembly of high-throughput sequencing data from three samples yielded contigs of 13,426 to 13,435nt, which represent the first complete genome sequences of soybean blotchy mosaic virus (SbBMV). SbBMV shows a typical cytorhabdovirus gene organization (3'-N-P-P3-M-G-L-5'), with each putative gene product being most similar, but with only 49.1-71.1% sequence identity, to those of cucurbit cytorhabdovirus 1. Given the species demarcation thresholds for rhabdoviruses, SbBMV is thus a distinct member of the genus Cytorhabdovirus.

Genomic characterization of a new torradovirus from common fleabane (Erigeron annuus).

A new virus was detected in common fleabane (Erigeron annuus) showing virus-like symptoms including leaf yellowing, mosaic, and mottling. This virus is tentatively named "fleabane yellow mosaic virus" (FbYMV). The complete genome sequence consists of two RNA segments of 7,133 nt (RNA 1) and 4,810 nt (RNA 2), excluding the poly(A) tract. Sequence analysis showed a genome organization comparable to that of members of the genus Torradovirus. The level of sequence identity between FbYMV and known members of the genus Torradovirus was below the cutoff established by the ICTV for species demarcation. Therefore, FbYMV should be classified as a new member of the genus Torradovirus.

Characterization of a ToMV isolate overcoming Tm-22 resistance gene in tomato.

Tomato mosaic virus (ToMV) is easily transmitted in soil and by contact. By these reasons, it is relatively difficult to control ToMV disease in tomato. Incorporation of the Tm-22 gene has been widely used as a control method for ToMV, but ToMV isolates that overcome this resistance gene have been reported worldwide in recent years. In this study, we determined the entire nucleotide sequences of ToMV isolate [named ToMV-KMT (LC650928)], which was isolated from tomato plants showing symptoms of systemic necrosis in Kumamoto prefecture, Japan. We also analyzed the viral gene of ToMV-KMT that overcome the Tm-22 gene by constructing its infectious cDNA clone and by generating chimeric viruses with a non-breaking strain. According to previous research, Tm-22 recognizes the viral movement protein (MP) and exerts resistance by inducing hypersensitive reaction or hypersensitive cell death. We discovered that a mutation in the 240th amino acid (aspartic acid to tyrosine) of the MP of ToMV-KMT, which may stabilize the protein's structure, is responsible for the ability of this isolate to overcome the resistance of Tm-22.

Systematic identification of miRNA-regulatory networks unveils their potential roles in sugarcane response to Sorghum mosaic virus infection.

BACKGROUND: Sugarcane mosaic disease (SMD) is a major viral disease of sugarcane (Saccharum spp.) worldwide. Sorghum mosaic virus (SrMV) is the dominant pathogen of SMD in the sugarcane planting areas of China. There is no report on miRNAs and their regulatory networks in sugarcane response to SrMV infection. RESULTS: In this study, small RNA sequencing (sRNA-seq) of samples from the leaves of SMD-susceptible variety ROC22 and -resistant variety FN39 infected by SrMV was performed. A total of 132 mature miRNAs (55 known miRNAs and 77 novel miRNAs) corresponding to 1,037 target genes were identified. After the SrMV attack, there were 30 differentially expressed miRNAs (17 up-regulated and 13 down-regulated) in FN39 and 19 in ROC22 (16 up-regulated and 3 down-regulated). Besides, there were 18 and 7 variety-specific differentially expressed miRNAs for FN39 and ROC22, respectively. KEGG enrichment analysis showed that the differentially expressed miRNAs targeted genes involved in several disease resistance-related pathways, such as mRNA surveillance, plant pathway interaction, sulfur metabolism, and regulation of autophagy. The reliability of sequencing data, and the expression patterns / regulation relationships between the selected differentially expressed miRNAs and their target genes in ROC22 and FN39 were confirmed by quantitative real-time PCR. A regulatory network diagram of differentially expressed miRNAs and their predicted target genes in sugarcane response to SrMV infection was sketched. In addition, precursor sequences of three candidate differentially expressed novel miRNAs (nov_3741, nov_22650 and nov_40875) were cloned from the ROC22 leaf infected by SrMV. Transient overexpression demonstrated that they could induce the accumulation of hydrogen peroxide and the expression level of hypersensitive response marker genes, salicylic acid-responsive genes and ethylene synthesis-depended genes in Nicotiana benthamiana. It is thus speculated that these three miRNAs may be involved in regulating the early immune response of sugarcane plants following SrMV infection. CONCLUSIONS: This study lays a foundation for revealing the miRNA regulation mechanism in the interaction of sugarcane and SrMV, and also provides a resource for miRNAs and their predicted target genes for SrMV resistance improvement in sugarcane.

Complete genome sequence of a novel potyvirus infecting Miscanthus sinensis (silver grass).

Here, we describe the full-length genome sequence of a novel potyvirus, tentatively named "Miscanthus sinensis mosaic virus" (MsiMV), isolated from Miscanthus sinensis (silver grass) held in a post-entry quarantine facility after being imported into Western Australia, Australia. The MsiMV genome is 9604 nucleotides (nt) in length, encoding a 3071-amino-acid (aa) polyprotein with conserved sequence motifs. The MsiMV genome is most closely related to that of sorghum mosaic virus (SrMV), with 74% nt and 78.5% aa sequence identity to the SrMV polyprotein region. Phylogenetic analysis based on the polyprotein grouped MsiMV with SrMV, sugarcane mosaic virus (SCMV), and maize dwarf mosaic virus (MDMV). This is the first report of a novel monopartite ssRNA virus in Miscanthus sinensis related to members of the genus Potyvirus in the family Potyviridae.