N6-methyladenosine RNA modification promotes viral genomic RNA stability and infection

Transcriptome-wide m6A methylation profile reveals its potential role underlying drought response in wheat (Triticum aestivum L.)

MAIN CONCLUSION

This study revealed the transcriptome-wide m6A methylation profile under drought stress and found that TaETC9 might regulate drought tolerance through mediating RNA methylation in wheat. Drought is one of the most destructive environmental constraints limiting crop growth and development. N6-methyladenosine (m6A) is a prevalent and important post-transcriptional modification in various eukaryotic RNA molecules, playing the crucial role in regulating drought response in plants. However, the significance of m6A in wheat (Triticum aestivum L.), particularly its involvment in drought response, remains underexplored. In this study, we investigated the transcriptome-wide m6A profile under drought stress using parallel m6A immunoprecipitation sequencing (MeRIP-seq). Totally, 4221 m6A peaks in 3733 m6A-modified genes were obtained, of which 373 methylated peaks exhibited differential expression between the control (CK) and drought-stressed treatments. These m6A loci were significantly enriched in proximity to stop codons and within the 3'-untranslated region. Integration of MeRIP-seq and RNA-seq revealed a positive correlation between m6A methylation and mRNA abundance and the genes displaying both differential methylation and expression were obtained. Finally, qRT-PCR analyses were further performed and the results found that the m6A-binding protein (TaETC9) showed significant up-regulation, while the m6A demethylase (TaALKBH10B) was significantly down-regulated under drought stress, contributing to increased m6A levels. Furthermore, the loss-of-function mutant of TaECT9 displayed significantly higher drought sensitivity compared to the wild type, highlighting its role in regulating drought tolerance. This study reported the first wheat m6A profile associated with drought stress, laying the groundwork for unraveling the potential role of RNA methylation in drought responses and enhancing stress tolerance in wheat through epigenetic approaches.

Detection, distribution, and functions of RNA N 6-methyladenosine (m6A) in plant development and environmental signal responses

The epitranscriptomic mark N 6-methyladenosine (m6A) is the most common type of messenger RNA (mRNA) post-transcriptional modification in eukaryotes. With the discovery of the demethylase FTO (FAT MASS AND OBESITY-ASSOCIATED PROTEIN) in Homo Sapiens, this modification has been proven to be dynamically reversible. With technological advances, research on m6A modification in plants also rapidly developed. m6A modification is widely distributed in plants, which is usually enriched near the stop codons and 3'-UTRs, and has conserved modification sequences. The related proteins of m6A modification mainly consist of three components: methyltransferases (writers), demethylases (erasers), and reading proteins (readers). m6A modification mainly regulates the growth and development of plants by modulating the RNA metabolic processes and playing an important role in their responses to environmental signals. In this review, we briefly outline the development of m6A modification detection techniques; comparatively analyze the distribution characteristics of m6A in plants; summarize the methyltransferases, demethylases, and binding proteins related to m6A; elaborate on how m6A modification functions in plant growth, development, and response to environmental signals; and provide a summary and outlook on the research of m6A in plants.

N6-Methyladenosine (m6A) Sequencing Reveals Heterodera glycines-Induced Dynamic Methylation Promoting Soybean Defense

Unraveling the intricacies of soybean cyst nematode (Heterodera glycines) race 4 resistance and susceptibility in soybean breeding lines-11-452 (highly resistant) and Dongsheng1 (DS1, highly susceptible)-was the focal point of this study. Employing cutting-edge N6-methyladenosine (m6A) and RNA sequencing techniques, we delved into the impact of m6A modification on gene expression and plant defense responses. Through the evaluation of nematode development in both resistant and susceptible roots, a pivotal time point (3 days postinoculation) for m6A methylation sequencing was identified. Our sequencing data exhibited robust statistics, successful soybean genome mapping, and prevalent m6A peak distributions, primarily in the 3' untranslated region and stop codon regions. Analysis of differential methylation peaks and differentially expressed genes revealed distinctive patterns between resistant and susceptible genotypes. In the highly resistant line (11-452), key resistance and defense-associated genes displayed increased expression coupled with inhibited methylation, encompassing crucial players such as R genes, receptor kinases, and transcription factors. Conversely, the highly susceptible DS1 line exhibited heightened expression correlated with decreased methylation in genes linked to susceptibility pathways, including Mildew Locus O-like proteins and regulatory elements affecting defense mechanisms. Genome-wide assessments, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses, and differential methylation peak/differentially expressed gene overlap emphasized the intricate interplay of m6A modifications, alternative splicing, microRNA, and gene regulation in plant defense. Protein-protein interaction networks illuminated defense-pivotal genes, delineating divergent mechanisms in resistant and susceptible responses. This study sheds light on the dynamic correlation between methylation, splicing, and gene expression, providing profound insights into plant responses to nematode infection.

The dynamics of N6-methyladenine RNA modification in resistant and susceptible rice varieties responding to rice stem borer damage

N6-methyladenosine (m6A) is the most prevalent modification in cellular RNA which orchestrates diverse physiological and pathological processes during stress response. However, the differential m6A modifications that cope with herbivore stress in resistant and susceptible crop varieties remain unclear. Here, we found that rice stem borer (RSB) larvae grew better on indica rice (e.g., MH63, IR64, Nanjing 11) than on japonica rice varieties (e.g., Nipponbare, Zhonghua 11, Xiushui 11). Then, transcriptome-wide m6A profiling of representative resistant (Nipponbare) and susceptible (MH63) rice varieties were performed using a nanopore direct RNA sequencing approach, to reveal variety-specific m6A modifications against RSB. Upon RSB infestation, m6A methylation occurred in actively expressed genes in Nipponbare and MH63, but the number of methylation sites decreased across rice chromosomes. Integrative analysis showed that m6A methylation levels were closely associated with transcriptional regulation. Genes involved in herbivorous resistance related to mitogen-activated protein kinase, jasmonic acid (JA), and terpenoid biosynthesis pathways, as well as JA-mediated trypsin protease inhibitors, were heavily methylated by m6A, and their expression was more pronounced in RSB-infested Nipponbare than in RSB-infested MH63, which may have contributed to RSB resistance in Nipponbare. Therefore, dynamics of m6A modifications act as the main regulatory strategy for expression of genes involved in plant-insect interactions, which is attributed to differential responses of resistant and susceptible rice varieties to RSB infestation. These findings could contribute to developing molecular breeding strategies for controlling herbivorous pests.

Unveiling microbial diversity: harnessing long-read sequencing technology

Long-read sequencing has recently transformed metagenomics, enhancing strain-level pathogen characterization, enabling accurate and complete metagenome-assembled genomes, and improving microbiome taxonomic classification and profiling. These advancements are not only due to improvements in sequencing accuracy, but also happening across rapidly changing analysis methods. In this Review, we explore long-read sequencing's profound impact on metagenomics, focusing on computational pipelines for genome assembly, taxonomic characterization and variant detection, to summarize recent advancements in the field and provide an overview of available analytical methods to fully leverage long reads. We provide insights into the advantages and disadvantages of long reads over short reads and their evolution from the early days of long-read sequencing to their recent impact on metagenomics and clinical diagnostics. We further point out remaining challenges for the field such as the integration of methylation signals in sub-strain analysis and the lack of benchmarks.

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.

Genome-Wide Analysis and Identification of UDP Glycosyltransferases Responsive to Chinese Wheat Mosaic Virus Resistance in Nicotiana benthamiana

Glycosylation, a dynamic modification prevalent in viruses and higher eukaryotes, is principally regulated by uridine diphosphate (UDP)-glycosyltransferases (UGTs) in plants. Although UGTs are involved in plant defense responses, their responses to most pathogens, especially plant viruses, remain unclear. Here, we aimed to identify UGTs in the whole genome of Nicotiana benthamiana (N. benthamiana) and to analyze their function in Chinese wheat mosaic virus (CWMV) infection. A total of 147 NbUGTs were identified in N. benthamiana. To conduct a phylogenetic analysis, the UGT protein sequences of N. benthamiana and Arabidopsis thaliana were aligned. The gene structure and conserved motifs of the UGTs were also analyzed. Additionally, the physicochemical properties and predictable subcellular localization were examined in detail. Analysis of cis-acting elements in the putative promoter revealed that NbUGTs were involved in temperature, defense, and hormone responses. The expression levels of 20 NbUGTs containing defense-related cis-acting elements were assessed in CWMV-infected N. benthamiana, revealing a significant upregulation of 8 NbUGTs. Subcellular localization analysis of three NbUGTs (NbUGT12, NbUGT16 and NbUGT17) revealed their predominant localization in the cytoplasm of N. benthamiana leaves, and NbUGT12 was also distributed in the chloroplasts. CWMV infection did not alter the subcellular localization of NbUGT12, NbUGT16, and NbUGT17. Transient overexpression of NbUGT12, NbUGT16, and NbUGT17 enhanced CWMV infection, whereas the knockdown of NbUGT12, NbUGT16 and NbUGT17 inhibited CWMV infection in N. benthamiana. These NbUGTs could serve as potential susceptibility genes to facilitate CWMV infection. Overall, the findings throw light on the evolution and function of NbUGTs.

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.

N6-methyladenosine modification positively regulate Japanese encephalitis virus replication

N6-methyladenosine (m6A) is present in diverse viral RNA and plays important regulatory roles in virus replication and host antiviral innate immunity. However, the role of m6A in regulating JEV replication has not been investigated. Here, we show that the JEV genome contains m6A modification upon infection of mouse neuroblast cells (neuro2a). JEV infection results in a decrease in the expression of m6A writer METTL3 in mouse brain tissue. METTL3 knockdown by siRNA leads to a substantial decrease in JEV replication and the production of progeny viruses at 48 hpi. Mechanically, JEV triggered a considerable increase in the innate immune response of METTL3 knockdown neuro2a cells compared to the control cells. Our study has revealed the distinctive m6A signatures of both the virus and host in neuro2a cells infected with JEV, illustrating the positive role of m6A modification in JEV infection. Our study further enhances understanding of the role of m6A modification in Flaviviridae viruses.

m6A modification of plant virus enables host recognition by NMD factors in plants

N6-methyladenosine (m6A) is the most abundant eukaryotic mRNA modification and is involved in various biological processes. Increasing evidence has implicated that m6A modification is an important anti-viral defense mechanism in mammals and plants, but it is largely unknown how m6A regulates viral infection in plants. Here we report the dynamic changes and functional anatomy of m6A in Nicotiana benthamiana and Solanum lycopersicum during Pepino mosaic virus (PepMV) infection. m6A modification in the PepMV RNA genome is conserved in these two species. Overexpression of the m6A writers, mRNA adenosine methylase A (MTA), and HAKAI inhibit the PepMV RNA accumulation accompanied by increased viral m6A modifications, whereas deficiency of these writers decreases the viral RNA m6A levels but enhances virus infection. Further study reveals that the cytoplasmic YTH-domain family protein NbECT2A/2B/2C as m6A readers are involved in anti-viral immunity. Protein-protein interactions indicate that NbECT2A/2B/2C interact with nonsense-mediated mRNA decay (NMD)-related proteins, including NbUPF3 and NbSMG7, but not with NbUPF1. m6A modification-mediated restriction to PepMV infection is dependent on NMD-related factors. These findings provide new insights into the functionality of m6A anti-viral activity and reveal a distinct immune response that NMD factors recognize the m6A readers-viral m6A RNA complex for viral RNA degradation to limit virus infection in plants.

Methyltransferase-like (METTL) homologues participate in Nicotiana benthamiana antiviral responses

Methyltransferase (MTase) enzymes catalyze the addition of a methyl group to a variety of biological substrates. MTase-like (METTL) proteins are Class I MTases whose enzymatic activities contribute to the epigenetic and epitranscriptomic regulation of multiple cellular processes. N⁶-adenosine methylation (m⁶A) is a common chemical modification of eukaryotic and viral RNA whose abundance is jointly regulated by MTases and METTLs, demethylases, and m⁶A binding proteins. m⁶A affects various cellular processes including RNA degradation, post-transcriptional processing, and antiviral immunity. Here, we used Nicotiana benthamiana and plum pox virus (PPV), an RNA virus of the Potyviridae family, to investigated the roles of MTases in plant-virus interaction. RNA sequencing analysis identified MTase transcripts that are differentially expressed during PPV infection; among these, accumulation of a METTL gene was significantly downregulated. Two N. benthamiana METTL transcripts (NbMETTL1 and NbMETTL2) were cloned and further characterized. Sequence and structural analyses of the two encoded proteins identified a conserved S-adenosyl methionine (SAM) binding domain, showing they are SAM-dependent MTases phylogenetically related to human METTL16 and Arabidopsis thaliana FIONA1. Overexpression of NbMETTL1 and NbMETTL2 caused a decrease of PPV accumulation. In sum, our results indicate that METTL homologues participate in plant antiviral responses.

N-linked glycoproteome analysis reveals central glycosylated proteins involved in response to wheat yellow mosaic virus in wheat

Glycosylation is an important proteins post-translational modification and is involved in protein folding, stability and enzymatic activity, which plays a crucial role in regulating protein function in plants. Here, we report for the first time on the changes of N-glycoproteome in wheat response to wheat yellow mosaic virus (WYMV) infection. Quantitative analyses of N-linked glycoproteome were performed in wheat without and with WYMV infection by ZIC-HILIC enrichment method combined with LC-MS/MS. Altogether 1160 N-glycopeptides and 971 N-glycosylated sites corresponding to 734 N-glycoproteins were identified, of which 64 N-glycopeptides and 64 N-glycosylated sites in 60 N-glycoproteins were significantly differentially expressed. Two conserved typical N-glycosylation motifs N-X-T and N-X-S and a nontypical motifs N-X-C were enriched in wheat. Gene Ontology analysis showed that most differentially expressed proteins were mainly enriched in metabolic process, catalytic activity and response to stress. Kyoto Encyclopedia of Genes and Genomes analysis indicated that two significantly changed glycoproteins were specifically related to plant-pathogen interaction. Furthermore, we found that over-expression of TaCERK reduced WYMV accumulation. Glycosylation site mutation further suggested that N-glycosylation of TaCERK could regulate wheat resistance to WYMV. This study provides a new insight for the regulation of protein N-glycosylation in defense response of plant.

Roles of RNA m6A modifications in plant-virus interactions

Viral RNAs have been known to contain N6-methyladenosine (m6A) modifications since the 1970s. The function of these modifications remained unknown until the development of genome-wide methods to map m6A residues. Increasing evidence has recently revealed a strong association between m6A modifications and plant viral infection. This highlight introduces advances in the roles of RNA m6A modifications in plant-virus interactions.

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.

The Roles of N6-Methyladenosine Modification in Plant-RNA Virus Interactions

N6-methyladenosine (m6A) is a dynamic post-transcriptional RNA modification. Recently, its role in viruses has led to the study of viral epitranscriptomics. m6A has been observed in viral genomes and alters the transcriptomes of both the host cell and virus during infection. The effects of m6A modifications on host plant mRNA can either increase the likelihood of viral infection or enhance the resistance of the host to the virus. However, to date, the regulatory mechanisms of m6A in viral infection and host immune responses have not been fully elucidated. With the development of sequencing-based biotechnologies, the study of m6A in plant viruses has received increasing attention. In this mini review, we summarize the positive and negative consequences of m6A modification in different RNA viral infections. Given its increasingly important roles in multiple viruses, m6A represents a new potential target for antiviral defense.

Plant YTHDF proteins are direct effectors of antiviral immunity against an N6-methyladenosine-containing RNA virus

In virus-host interactions, nucleic acid-directed first lines of defense that allow viral clearance without compromising growth are of paramount importance. Plants use the RNA interference pathway as a basal antiviral immune system, but additional RNA-based mechanisms of defense also exist. The infectivity of a plant positive-strand RNA virus, alfalfa mosaic virus (AMV), relies on the demethylation of viral RNA by the recruitment of the cellular N6-methyladenosine (m6 A) demethylase ALKBH9B, but how demethylation of viral RNA promotes AMV infection remains unknown. Here, we show that inactivation of the Arabidopsis cytoplasmic YT521-B homology domain (YTH)-containing m6 A-binding proteins ECT2, ECT3, and ECT5 is sufficient to restore AMV infectivity in partially resistant alkbh9b mutants. We further show that the antiviral function of ECT2 is distinct from its previously demonstrated function in the promotion of primordial cell proliferation: an ect2 mutant carrying a small deletion in its intrinsically disordered region is partially compromised for antiviral defense but not for developmental functions. These results indicate that the m6 A-YTHDF axis constitutes a novel branch of basal antiviral immunity in plants.

Genome-Wide Identification, Expression and Evolution Analysis of m6A Writers, Readers and Erasers in Aegilops_tauschii

N6-methyladenosine modifications (m6A) is one of the most abundant and prevalent post-transcriptional RNA modifications in plants, playing the crucial role in plant growth and development and stress adaptation. However, the m6A regulatory machinery in Aegilops_tauschii, the D genome progenitor of common wheat, is not well understood at present. Here, we systematically identified the m6A-related genes in Aegilops with a genome-wide search approach. In total, 25 putative m6A genes composed of 5 writers, 13 readers and 7 erasers were obtained. A phylogenetic analysis clearly grouped them into three subfamilies with the same subfamily showing similar gene structures and conserved domains. These m6A genes were found to contain a large number of cis-acting elements associating with plant hormones, regulation of growth and development as well as stress response, suggesting their widespread regulation function. Furthermore, the expression profiling of them was investigated using RNA-seq data to obtain stress-responsive candidates, of which 5 were further validated with a qPCR analysis. Finally, the genetic variation of m6A-related genes was investigated between Aegilops and D subgenome of wheat based on re-sequencing data, and an obvious genetic bottleneck occurred on them during the wheat domestication process. The promising haplotype association with domestication and agronomic traits was also detected. This study provided some insights on the genomic organization and evolutionary features of m6A-related genes in Aegilops, which will facilitate the further functional study and also contribute to broaden the genetic basis for genetic improvement in wheat and other crops.

The emerging role of N6-methyladenine RNA methylation in metal ion metabolism and metal-induced carcinogenesis

N⁶-methyladenine (m⁶A) is the most common and abundant internal modification in eukaryotic mRNAs, which can regulate gene expression and perform important biological tasks. Metal ions participate in nucleotide biosynthesis and repair, signal transduction, energy generation, immune defense, and other important metabolic processes. However, long-term environmental and occupational exposure to metals through food, air, soil, water, and industry can result in toxicity, serious health problems, and cancer. Recent evidence indicates dynamic and reversible m⁶A modification modulates various metal ion metabolism, such as iron absorption, calcium uptake and transport. In turn, environmental heavy metal can alter m⁶A modification by directly affecting catalytic activity and expression level of methyltransferases and demethylases, or through reactive oxygen species, eventually disrupting normal biological function and leading to diseases. Therefore, m⁶A RNA methylation may play a bridging role in heavy metal pollution-induced carcinogenesis. This review discusses interaction among heavy metal, m⁶A, and metal ions metabolism, and their regulatory mechanism, focuses on the role of m⁶A methylation and heavy metal pollution in cancer. Finally, the role of nutritional therapy that targeting m⁶A methylation to prevent metal ion metabolism disorder-induced cancer is summarized.

Genome-Wide Identification and Functional Analysis of NAP1 in Triticum aestivum

As a main molecular chaperone of histone H2A-H2B, nucleosome assembly protein 1 (NAP1) has been widely researched in many species. However, there is little research investigating the function of NAP1 in Triticum aestivum. To understand the capabilities of the family of NAP1 genes in wheat and the relationship between TaNAP1 genes and plant viruses, we performed comprehensive genome-wide analysis and quantitative real-time polymerase chain reaction (qRT-PCR) for testing expression profiling under hormonal and viral stresses. Our results showed that TaNAP1 was expressed at different levels in different tissues, with higher expression in tissues with high meristematic capacity, such as roots. Furthermore, the TaNAP1 family may participate in plant defense mechanisms. This study provides a systematic analysis of the NAP1 gene family in wheat and lays the foundation for further studies on the function of TaNAP1 in the response of wheat plants to viral infection.

A cell wall invertase modulates resistance to fusarium crown rot and sharp eyespot in common wheat

Fusarium crown rot (FCR) and sharp eyespot (SE) are serious soil-borne diseases in wheat and its relatives that have been reported to cause wheat yield losses in many areas. In this study, the expression of a cell wall invertase gene, TaCWI-B1, was identified to be associated with FCR resistance through a combination of bulk segregant RNA sequencing and genome resequencing in a recombinant inbred line population. Two bi-parental populations were developed to further verify TaCWI-B1 association with FCR resistance. Overexpression lines and ethyl methanesulfonate (EMS) mutants revealed TaCWI-B1 positively regulating FCR resistance. Determination of cell wall thickness and components showed that the TaCWI-B1-overexpression lines exhibited considerably increased thickness and pectin and cellulose contents. Furthermore, we found that TaCWI-B1 directly interacted with an alpha-galactosidase (TaGAL). EMS mutants showed that TaGAL negatively modulated FCR resistance. The expression of TaGAL is negatively correlated with TaCWI-B1 levels, thus may reduce mannan degradation in the cell wall, consequently leading to thickening of the cell wall. Additionally, TaCWI-B1-overexpression lines and TaGAL mutants showed higher resistance to SE; however, TaCWI-B1 mutants were more susceptible to SE than controls. This study provides insights into a FCR and SE resistance gene to combat soil-borne diseases in common wheat.

Genetic resistance in barley against Japanese soil-borne wheat mosaic virus functions in the roots

Infection by the Japanese soil-borne wheat mosaic virus (JSBWMV) can lead to substantial losses in the grain yield of barley and wheat crops. While genetically based resistance to this virus has been documented, its mechanistic basis remains obscure. In this study, the deployment of a quantitative PCR assay showed that the resistance acts directly against the virus rather than by inhibiting the colonization of the roots by the virus' fungal vector Polymyxa graminis. In the susceptible barley cultivar (cv.) Tochinoibuki, the JSBWMV titre was maintained at a high level in the roots during the period December-April, and the virus was translocated from the root to the leaf from January onwards. In contrast, in the roots of both cv. Sukai Golden and cv. Haruna Nijo, the titre was retained at a low level, and translocation of the virus to the shoot was strongly suppressed throughout the host's entire life cycle. The roots of wild barley (Hordeum vulgare ssp. spontaneum) accession H602 responded in the early stages of infection similarly to those of the resistant cultivated forms, but the host was unable to suppress the translocation of the virus to the shoot from March onwards. The virus titre in the root was presumed to have been restricted by the action of the gene product of Jmv1 (on chromosome 2H), while the stochastic nature of the infection was suppressed by the action of that of Jmv2 (on chromosome 3H), a gene harbored by cv. Sukai Golden but not by either cv. Haruna Nijo or accession H602.