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.

Mapping of quantitative trait loci for leaf rust resistance in the wheat population 'Xinmai 26/Zhoumai 22'.

Leaf rust, caused by the fungal pathogen Puccinia triticina (Pt), is one of the major and dangerous diseases of wheat, and has caused serious yield loss of wheat worldwide. Here, we investigated adult-plant resistance (APR) to leaf rust in a recombinant inbred line (RIL) population derived from 'Xinmai 26' and 'Zhoumai 22' over 3 years. Linkage mapping for APR to leaf rust revealed four quantitative trait loci (QTL) in this RIL population. Two QTL, QLr.hnau-2BS and QLr.hnau-3BS were contributed by 'Zhoumai22', whereas QLr.hnau-2DS and QLr.hnau-5AL were contributed by 'Xinmai 26'. The QLr.hnau-2BS covering a race-specific resistance gene Lr13 showed the most stable APR to leaf rust. Overexpression of Lr13 significantly increased APR to leaf rust. Interestingly, we found that a CNL(coiled coil-nucleotide-binding site-leucine-rich repeat)-like gene, TaCN, in QLr.hnau-2BS completely co-segregated with leaf rust resistance. The resistant haplotype TaCN-R possessed half the sequence of the coiled-coil domain of TaCN protein. Lr13 strongly interacted with TaCN-R, but did not interact with the full-length TaCN (TaCN-S). In addition, TaCN-R was significantly induced after Pt inoculation and changed the sub-cellular localization of Lr13 after interaction. Therefore, we hypothesized that TaCN-R mediated leaf rust resistance possibly by interacting with Lr13. This study provides important QTL for APR to leaf rust, and new insights into understanding how a CNL gene modulates disease resistance in common wheat.

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

Molecular manipulation of susceptibility (S) genes that are antipodes to resistance (R) genes has been adopted as an alternative strategy for controlling crop diseases. Here, we show the S gene encoding Triticum aestivum m6A methyltransferase B (TaMTB) is identified by a genome-wide association study and subsequently shown to be a positive regulator for wheat yellow mosaic virus (WYMV) infection. TaMTB is localized in the nucleus, is translocated into the cytoplasmic aggregates by binding to WYMV NIb to upregulate the m6A level of WYMV RNA1 and stabilize the viral RNA, thus promoting viral infection. A natural mutant allele TaMTB-SNP176C is found to confer an enhanced susceptibility to WYMV infection through genetic variation analysis on 243 wheat varieties. Our discovery highlights this allele can be a useful target for the molecular wheat breeding in the future.

Changes in soil fungal communities after onset of wheat yellow mosaic virus disease.

Rhizosphere-associated microbes have important implications for plant health, but knowledge of the association between the pathological conditions of soil-borne virus-infected wheat and soil microbial communities, especially changes in fungal communities, remains limited. We investigated the succession of fungal communities from bulk soil to wheat rhizosphere soil in both infected and healthy plants using amplicon sequencing methods, and assessed their potential role in plant health. The results showed that the diversity of fungi in wheat rhizosphere and bulk soils significantly differed post wheat yellow mosaic virus disease onset. The structure differences in fungal community at the two wheat health states or two compartment niches were evident, soil physicochemical properties (i.e., NH4 +) contribute to differences in fungal community structure and alpha diversity. Comparison analysis showed Mortierellomycetes and Dothideomycetes as dominant communities in healthy wheat soils at class level. The genus Pyronemataceae and Solicoccozyma were significantly are significantly enriched in rhizosphere soil of diseased plant, the genus Cystofilobasidium, Cladosporium, Mortierella, and Stephanonectria are significantly enriched in bulk soil of healthy plant. Co-occurrence network analysis showed that the fungi in healthy wheat soil has higher mutual benefit and connectivity compared with diseased wheat. The results of this study demonstrated that the occurrence of wheat yellow mosaic virus diseases altered both fungal community diversity and composition, and that NH4 + is the most important soil physicochemical factor influencing fungal diversity and community composition.

Central Role of Ubiquitination in Wheat Response to CWMV Infection.

Ubiquitination is a major post-translational modification (PTM) involved in almost all eukaryotic biological processes and plays an essential role in plant response to pathogen infection. However, to date, large-scale profiling of the changes in the ubiquitome in response to pathogens, especially viruses, in wheat has not been reported. This study aimed to identify the ubiquitinated proteins involved in Chinese wheat mosaic virus (CWMV) infection in wheat using a combination of affinity enrichment and high-resolution liquid chromatography-tandem mass spectroscopy. The potential biological functions of these ubiquitinated proteins were further analyzed using bioinformatics. A total of 2297 lysine ubiquitination sites in 1255 proteins were identified in wheat infected with CWMV, of which 350 lysine ubiquitination sites in 192 proteins were differentially expressed. These ubiquitinated proteins were related to metabolic processes, responses to stress and hormones, plant-pathogen interactions, and ribosome pathways, as assessed via Gene ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses. Furthermore, we found that the ubiquitination of Ta14-3-3 and TaHSP90, which are essential components of the innate immune system, was significantly enhanced during CWMV infection, which suggested that ubiquitination modification plays a vital role in the regulatory network of the host response to CWMV infection. In summary, our study puts forward a novel strategy for further probing the molecular mechanisms of CWMV infection. Our findings will inform future research to find better, innovative, and effective solutions to deal with CWMV infection in wheat, which is the most crucial and widely used cereal grain crop.

Genome-Wide Identification and Characterization of Long Noncoding RNAs Involved in Chinese Wheat Mosaic Virus Infection of Nicotiana benthamiana.

Recent studies have shown that a large number of long noncoding RNAs (lncRNAs) can regulate various biological processes in animals and plants. Although lncRNAs have been identified in many plants, they have not been reported in the model plant Nicotiana benthamiana. Particularly, the role of lncRNAs in plant virus infection remains unknown. In this study, we identified lncRNAs in N. benthamiana response to Chinese wheat mosaic virus (CWMV) infection by RNA sequencing. A total of 1175 lncRNAs, including 65 differentially expressed lncRNAs, were identified during CWMV infection. We then analyzed the functions of some of these differentially expressed lncRNAs. Interestingly, one differentially expressed lncRNA, XLOC_006393, was found to participate in CWMV infection as a precursor to microRNAs in N. benthamiana. These results suggest that lncRNAs play an important role in the regulatory network of N. benthamiana in response to CWMV infection.

Transgenic Nicotiana benthamiana plants expressing a hairpin RNAi construct of a nematode Rs-cps gene exhibit enhanced resistance to Radopholus similis.

Burrowing nematodes (Radopholus similis) cause severe harm in many agronomic and horticultural crops and are very difficult to manage. Cathepsin S is one of the most important cysteine proteinases and plays key roles in nematodes and many other parasites. To evaluate the effect of in planta RNAi on the control of this nematode, a specific fragment from the protease gene, cathepsin S (Rs-cps), was cloned into the binary vector pFGC5941 in the forward and reverse orientations to construct recombinant plant RNAi vectors. Transgenic Nicotiana benthamiana plants expressing Rs-cps dsRNA were obtained and studied. The transcript abundance of Rs-cps dsRNA appeared to be diverse in the different transgenic lines. Moreover, the bioassay results revealed that Rs-cps transgenic N. benthamiana plants were resistant to R. similis and the transcription level of Rs-cps in R. similis was drastically decreased. In addition, the reproduction and hatching rate of R. similis isolated from the Rs-cps transgenic plants were also significantly reduced. Our results suggest that Rs-cps is essential for the reproduction and pathogenicity of R. similis. This is the first study to employ in planta RNAi approach to target the Rs-cps gene for the control of plant parasitic nematodes.