First report of potato virus H infecting tomato (Solanum lycopersicum) in China.

Potato virus H (PVH), belonging to the genus Carlavirus in the family Betaflexiviridae, was initially discovered in potato plants in Inner Mongolia, China (Li et al., 2013). Subsequently, it was documented to infect pepino, a perennial shrub of the Solanaceae family like potatoes (Abouelnasr et al., 2014). Tomato (Solanum lycopersicum L.), a major global crop, faces threats from various plant viruses. In an open field survey in Yunnan, China during July 2023, tomatoes (cultivar: Liangsi) showed typical virus symptoms: leaf yellowing, curling, mottling, and fruit with abnormal shape and color. Eleven symptomatic tomato samples were collected for high-throughput sequencing to identify the potential pathogen. RNA sequencing libraries were prepared using the TruSeq RNA sample prep kit (Illumina, San Diego, CA, USA), followed by RNA-seq sequencing on an Illumina HiSeq4000 platform (LC Sciences, USA). Approximately 77,928,560 paired-end reads (150-bp each) were generated. After quality control, 75,808,296 reads were retained and subjected to de novo assembly using Trinity (version 2.8.5). The assembled contigs, ranging from 198 nt to 15865 nt, were used as queries to search against the NCBI non-redundant protein sequence database (NR) or nucleotide sequence database (NT) to detect the potential pathogens using BLASTx and BLASTn program with a cutoff e-value of 10-5. As a consequence, certain contigs were assigned to 3 plant viruses, including PVH (the highest RdRp blastx identity to UAD82396.1: 97.8%), Capsicum chlorosis virus (CaCV, the highest RdRp blastx identity to APQ31267.1: 98.4%), and southern tomato virus (STV, the highest CP-RdRp fusion protein blastx identity to QOW17541.1: 99.74%). The presence of the identified 3 viruses was subsequently screened in the 11 tomato samples originally collected from the corresponding field. Notably, the specific detection primers for the PVH genome was designed from the newly assembled PVH genome (Forward primer: 5'- ATAGTTGTGCACTGTGTGCCTG-3'; Reverse primer: 5'-GCTTAAGGTTCTTAGCGTATTC-3'), targeting ~1.1kb. Consequently, PVH was detected in 3 out of 11 samples: 2 leaf samples and 1 fruit sample, with one leaf sample showing a single infection. The complete genome sequence of PVH in tomatoes (PVH-tomato) was successfully obtained by assembling nine overlapping regions spanning the entire PVH-tomato genome, following the RT-PCR and the 5' RACE and 3' RACE approaches, and deposited in NCBI nucleotide database with accession number OR397130.1Phylogenetic analysis based on the full genome sequences of PVH-tomato and other publicly available PVH isolates revealed that PVH-tomato was closely related to a PVH isolate found in potatoes in Yunnan (blastn similarity: 97.76%) (Fig. S1A). To test PVH-tomato infectivity and pathogenicity, four healthy Nicotiana benthamiana and four healthy tomato plants were mechanically inoculated with PVH-infected leaf sap; controls used sap from healthy plants. Three weeks post-inoculation, all N. benthamiana (4/4) and three tomato plants (3/4) were PVH-positive by RT-PCR. Symptoms were milder in N. benthamiana, and only two tomato plants (2/4) showed leaf curling. No PVH was detected in control samples (Figure S1B, S1C). Sanger sequencing confirmed the amplicons' expected length of 1093 bp. Previously, PVH was documented only in potato and pepino. This is the first report of tomatoes as natural PVH hosts and PVH infecting N. benthamiana under lab conditions.

Identification and Genome Characterization of a Novel Nege-like Virus Isolated from Aphids (Aphis gossypii) in Yunnan Province.

Negeviruses are insect-specific enveloped RNA viruses that exhibit a wide geographic distribution. A novel nege-like virus, tentatively named Aphis gossypii nege-like virus (AGNLV, GenBank: OR880429.1), was isolated from aphids (Aphis gossypii) in Lijiang City, Yunnan, China. AGNLV has a genome sequence of 9258 nt (excluding the polyA tail) encoding three open reading frames (ORFs). ORF1 (7149 nt) encodes a viral methyltransferase, a viral RNA helicase, and an RNA-dependent RNA polymerase. ORF2 (1422 nt) encodes a DiSB-ORF2_chro domain and ORF3 encodes an SP24 domain. The genome sequence of AGNLV shares the highest nucleotide identity of 60.0% and 59.5% with Wuhan house centipede virus 1 (WHCV1) and Astegopteryx formosana nege-like virus (AFNLV), respectively. Phylogenetic analysis based on the RNA-dependent RNA polymerase shows that AGNLV is clustered with other negeviruses and nege-like viruses discovered in aphids, forming a distinct "unclassified clade". Interestingly, AGNLV only encodes three ORFs, whereas AFNLV and WHCV1 have four ORFs. Structure and transmembrane domain predictions show the presence of eight alpha helices and five transmembrane helices in the AGNLV ORF3. Translational enhancement of the AGNLV 5' UTR was similar to that of the 5' UTR of plant viruses. Our findings provide evidence of the diversity and structure of nege-like viruses and are the first record of such a virus from a member of the genus Aphis.

Single-dose methamphetamine administration impairs ORM retrieval in mice via excessive DA-mediated inhibition of PrLGlu activity.

Methamphetamine (METH), an abused psychostimulant, impairs cognition through prolonged or even single-dose exposure, but animal experiments have shown contradictory effects on memory deficits. In this study we investigated the effects and underlying mechanisms of single-dose METH administration on the retrieval of object recognition memory (ORM) in mice. We showed that single-dose METH administration (2 mg/kg, i.p.) significantly impaired ORM retrieval in mice. Fiber photometry recording in METH-treated mice revealed that the activity of prelimbic cortex glutamatergic neurons (PrLGlu) was significantly reduced during ORM retrieval. Chemogenetic activation of PrLGlu or glutamatergic projections from ventral CA1 to PrL (vCA1Glu-PrL) rescued ORM retrieval impairment. Fiber photometry recording revealed that dopamine (DA) levels in PrL of METH-treated mice were significantly increased, and micro-infusion of the D2 receptor (D2R) antagonist sulpiride (0.25 µg/side) into PrL rescued ORM retrieval impairment. Whole-cell recordings in brain slices containing the PrL revealed that PrLGlu intrinsic excitability and basal glutamatergic synaptic transmission were significantly reduced in METH-treated mice, and the decrease in intrinsic excitability was reversed by micro-infusion of Sulpiride into PrL in METH-treated mice. Thus, the impaired ORM retrieval caused by single-dose METH administration may be attributed to reduced PrLGlu activity, possibly due to excessive DA activity on D2R. Selective activation of PrLGlu or vCA1Glu-PrL may serve as a potential therapeutic strategy for METH-induced cognitive dysfunction.

Complete genome sequence and genetic characterization of a novel segmented RNA virus infecting Nilaparvata lugens.

The brown planthopper (BPH), Nilaparvata lugens, is a significant agricultural pest capable of long-distance migration and transmission of viruses that cause severe disease in rice. In this study, we identified a novel segmented RNA virus in a BPH, and this virus exhibited a close relationship to members of a recently discovered virus lineage known as "quenyaviruses" within the viral kingdom Orthornavirae. This newly identified virus was named "Nilaparvata lugens quenyavirus 1" (NLQV1). NLQV1 consists of five positive-sense, single-stranded RNAs, with each segment containing a single open reading frame (ORF). The genomic characteristics and phylogenetic analysis support the classification of NLQV1 as a novel quenyavirus. Notably, all of the genome segments of NLRV contained the 5'-terminal sequence AUCUG. The characteristic virus-derived small interfering RNA (vsiRNA) profile of NLQV1 suggests that the antiviral RNAi pathway of the host BPH was activated in response to virus infection. These findings represent the first documented report of quenyaviruses in planthoppers, contributing to our understanding of quenyaviruses and expanding our knowledge of insect-specific viruses in planthoppers.

Metatranscriptome and small RNA sequencing revealed a mixed infection of newly identified bymovirus and bean yellow mosaic virus on peas.

Peas (Pisum sativum L.) are widely cultivated in temperate regions and are susceptible hosts for various viruses across different families. The discovery and identification of new viruses in peas has significant implications for field disease management. Here, we identified a mixed infection of two viruses from field-collected peas exhibiting virus-like symptoms using metatranscriptome and small RNA sequencing techniques. Upon identification, one of the viruses was determined to be a newly isolated and discovered bymovirus from peas, named "pea bymovirus 1 (PBV1)". The other was identified as a novel variant of bean yellow mosaic virus (BYMV-HZ1). Subsequently, mechanical inoculation and RT-PCR assays confirmed that both viruses could be inoculated back onto peas and tobaccos, showing mixed infection by PBV1 and BYMV-HZ1. To our knowledge, this is the first isolation of a bymovirus from pea and the first documented case of mixed infection of peas by PBV1 and BYMV-HZ1 in China.

Cross-kingdom RNA interference mediated by insect salivary microRNAs may suppress plant immunity.

Communication between insects and plants relies on the exchange of bioactive molecules that traverse the species interface. Although proteinic effectors have been extensively studied, our knowledge of other molecules involved in this process remains limited. In this study, we investigate the role of salivary microRNAs (miRNAs) from the rice planthopper Nilaparvata lugens in suppressing plant immunity. A total of three miRNAs were confirmed to be secreted into host plants during insect feeding. Notably, the sequence-conserved miR-7-5P is specifically expressed in the salivary glands of N. lugens and is secreted into saliva, distinguishing it significantly from homologues found in other insects. Silencing miR-7-5P negatively affects N. lugens feeding on rice plants, but not on artificial diets. The impaired feeding performance of miR-7-5P-silenced insects can be rescued by transgenic plants overexpressing miR-7-5P. Through target prediction and experimental testing, we demonstrate that miR-7-5P targets multiple plant genes, including the immune-associated bZIP transcription factor 43 (OsbZIP43). Infestation of rice plants by miR-7-5P-silenced insects leads to the increased expression of OsbZIP43, while the presence of miR-7-5P counteracts this upregulation effect. Furthermore, overexpressing OsbZIP43 confers plant resistance against insects which can be subverted by miR-7-5P. Our findings suggest a mechanism by which herbivorous insects have evolved salivary miRNAs to suppress plant immunity, expanding our understanding of cross-kingdom RNA interference between interacting organisms.

Complete genome analysis of a novel narnavirus in sweet viburnum (Viburnum odoratissimum).

Trees and shrubs provide important ecological services. However, few studies have surveyed the virome in trees and shrubs. In this study, we discovered a new positive-sense RNA virus originating from Viburnum odoratissimum, which we named "Vo narna-like virus". The complete genome of Vo narna-like virus is 3,451 nt in length with an open reading frame (ORF) encoding the RNA-dependent RNA polymerase (RdRP) protein. Phylogenetic analysis placed this virus within the betanarnavirus clade, sharing 53.63% amino acid sequence identity with its closest relative, Qingdao RNA virus 2. The complete sequence of the virus was confirmed by rapid amplification of cDNA ends (RACE) and Sanger sequencing. Small interfering RNA (siRNA) analysis indicated that this virus interacts with the RNA interference (RNAi) pathway of V. odoratissimum. This is the first report of a narnavirus in V. odoratissimum.

Histone deacetylase OsHDA706 orchestrates rice broad-spectrum antiviral immunity and is impeded by a viral effector.

Lysine acetylation is a dynamic post-translational modification of proteins. Extensive studies have revealed that the acetylation modulated by histone acetyltransferases and histone deacetylases (HDACs) plays a crucial role in regulating protein function. However, there has been limited focus on how HDACs regulate jasmonic acid (JA) biosynthesis in plants. Here, we uncover that the protein stability of OsLOX14, a critical enzyme involved in JA biosynthesis, is regulated by a histone deacetylase, OsHDA706, and is hindered by a viral protein. Our results show that OsHDA706 deacetylates OsLOX14 and enhances the stability of OsLOX14, leading to JA accumulation and an improved broad-spectrum rice antiviral defense. Furthermore, we found that the viral protein P2, encoded by the destructive rice stripe virus, disrupts the association of OsHDA706-OsLOX14, promoting viral infection. Overall, our findings reveal how HDAC manipulates the interplay of deacetylation and protein stability of a JA biosynthetic enzyme to enhance plant antiviral responses.

Identification and Genome Characterization of a Novel Virus within the Genus Totivirus from Chinese Bayberry (Myrica rubra).

Chinese bayberry (Myrica rubra) is an economically significant fruit tree native to eastern Asia and widely planted in south-central China. However, studies about the viruses infecting M. rubra remain largely lacking. In the present study, we employed the metatranscriptomic method to identify viruses in M. rubra leaves exhibiting yellowing and irregular margin symptoms collected in Fuzhou, a city located in China's Fujian province in the year 2022. As a consequence, a novel member of the genus Totivirus was identified and tentatively named "Myrica rubra associated totivirus 1" (MRaTV1). The genome sequencing of MRaTV1 was determined by overlapping reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The two deduced proteins encoded by MRaTV1 have the highest amino acid (aa) sequence identity to the coat protein (CP) and RNA-dependent RNA polymerase (RdRP) of Panax notoginseng virus A (PNVA), a member of the genus Totivirus within the family Totiviridae, at 49.7% and 61.7%, respectively. According to the results of the phylogenetic tree and the species demarcation criteria of the International Committee on Taxonomy of Viruses (ICTV) for the genus Totivirus, MRaTV1 is considered a new member of the genus Totivirus.

Molecular Characterization of an Isolate of Bean Common Mosaic Virus First Identified in Gardenia Using Metatranscriptome and Small RNA Sequencing.

Gardenia (Gardenia jasminoides) is a popular and economically vital plant known for its ornamental and medicinal properties. Despite its widespread cultivation, there has been no documentation of plant viruses on gardenia yet. In the present study, gardenia leaves exhibiting symptoms of plant viral diseases were sampled and sequenced by both metatranscriptome and small RNA sequencing. As a consequence, bean common mosaic virus (BCMV) was identified in gardenia for the first time and named BCMV-gardenia. The full genome sequence of BCMV-gardenia is 10,054 nucleotides (nt) in length (excluding the poly (A) at the 3' termini), encoding a large polyprotein of 3,222 amino acids. Sequence analysis showed that the N-termini of the polyprotein encoded by BCMV-gardenia is less conserved when compared to other BCMV isolates, whereas the C-termini is the most conserved. Maximum likelihood phylogenetic analysis showed that BCMV-gardenia was clustered closely with other BCMV isolates identified outside the leguminous plants. Our results indicated that the majority of BCMV-gardenia virus-derived small interfering RNAs (vsiRNAs) were 21 nt and 22 nt, with 21 nt being more abundant. The first nucleotide at the 5' termini of vsiRNAs derived from BCMV-gardenia preferred U and A. The ratio of vsiRNAs derived from sense (51.1%) and antisense (48.9%) strands is approaching, and the distribution of vsiRNAs along the viral genome is generally even, with some hot spots forming in local regions. Our findings could provide new insights into the diversity, evolution, and host expansion of BCMV and contribute to the prevention and treatment of this virus.

Complete genome sequence of a novel robigovirus infecting Mentha arvensis.

The complete genomic sequence of a novel robigovirus, provisionally named "Mentha arvensis robigovirus 1" (MARV1), was determined by combining next-generation sequencing (NGS), reverse transcription polymerase chain reaction (RT-PCR), and rapid amplification of cDNA ends (RACE) PCR. The complete genomic sequence of this new virus is 7617 nucleotides in length, excluding the 3' poly(A) tail. The MARV1 genome encodes a putative replicase, "triple gene block" proteins, and a coat protein. Phylogenetic analysis demonstrated that MARV1 is a member of the genus Robigovirus, with closest relationships to African oil palm ringspot virus (AOPRV). Furthermore, MARV1-derived small interfering RNAs (siRNAs) showed typical patterns of plant-virus-derived siRNAs produced by the host antiviral RNA interference pathway. This is the first report of a plant virus of the genus Robigovirus in M. arvensis.