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.

The sunflower, an important oilseed crop and food source across the world, is susceptible to several pathogens, which cause severe losses in sunflower production. The utilization of genetic resistance is the most economical, effective measure to prevent infectious diseases. Based on the sunflower pangenome, in this study, we explored the variability of resistance gene analogs (RGAs) within the species. According to a comparative analysis of RGA candidates in the sunflower pangenome using the RGAugury pipeline, a total of 1344 RGAs were identified, comprising 1107 conserved, 199 varied, and 38 rare RGAs. We also identified RGAs associated with resistance against Sclerotinia sclerotiorum (S. sclerotiorum) in sunflower at the quantitative trait locus (QTL). A total of 61 RGAs were found to be located at four quantitative trait loci (QTLs). Through a detailed expression analysis of RGAs in one susceptible and two tolerant sunflower inbred lines (ILs) across various time points post inoculation, we discovered that 348 RGAs exhibited differential expression in response to Sclerotinia head rot (SHR), with 17 of these differentially expressed RGAs being situated within the QTL regions. In addition, 15 RGA candidates had gene introgression. Our data provide a better understanding of RGAs, which facilitate genomics-based improvements in disease resistance in sunflower.

Objective In phytopathogenic fungi, several metalloproteinase have been implicated in virulence, but pathogenesis roles in rust are largely unknown. Here, we identified a M36 family metalloproteases from Puccina helianthi genome, designated PhMEP1, aimed to reveal the biological characteristics related to pathogenicity.Result Bioinformatics analysis showed that PhMEP1contains some of the conserved zinc-binding and active site motifs characteristics of metalloproteinase which might well be a new fungalysin-like peptidase in the M36 family. The PhMEP1 protein was over expressed as inclusion bodies in Escherichia coli. The recombinant expression products of PhMEP1 could hydrolyze azocasein and the hydrolytic activity was suppressed by metal ion chelating agents such as 1,10-phenanthroline and ethylene diamine tetraacetic acid (EDTA). The subcellular localization of PhMEP1 was detected by confocal laser scanning microscopy of the leaves from a 2-day-old Nicotiana benthamiana seedlings expressed PhMEP1-GFP fusion that showed green fluorescent protein (GFP) signal accumulated in the plasma membrane of epithelial cells.Conclusion PhMEP1 may serve as a pathogenicity factor contributing to P. helianthi penetration and infection.