Abstract
BackgroundCucumber green mottle mosaic virus (CGMMV) causes substantial global losses in cucurbit crops, especially watermelon. N6-methyladenosine (m6A) methylation in RNA is one of the most important post-transcriptional modification mechanisms in eukaryotes. It has been shown to have important regulatory functions in some model plants, but there has been no research regarding m6A modifications in watermelon.ResultsWe measured the global m6A level in resistant watermelon after CGMMV infection using a colorimetric method. And the results found that the global m6A level significantly decreased in resistant watermelon after CGMMV infection. Specifically, m6A libraries were constructed for the resistant watermelon leaves collected 48 h after CGMMV infection and the whole-genome m6A-seq were carried out. Numerous m6A modified peaks were identified from CGMMV-infected and control (uninfected) samples. The modification distributions and motifs of these m6A peaks were highly conserved in watermelon transcripts but the modification was more abundant than in other reported crop plants. In early response to CGMMV infection, 422 differentially methylated genes (DMGs) were identified, most of which were hypomethylated, and probably associated with the increased expression of watermelon m6A demethylase gene ClALKBH4B. Gene Ontology (GO) analysis indicated quite a few DMGs were involved in RNA biology and stress responsive pathways. Combined with RNA-seq analysis, there was generally a negative correlation between m6A RNA methylation and transcript level in the watermelon transcriptome. Both the m6A methylation and transcript levels of 59 modified genes significantly changed in response to CGMMV infection and some were involved in plant immunity.ConclusionsOur study represents the first comprehensive characterization of m6A patterns in the watermelon transcriptome and helps to clarify the roles and regulatory mechanisms of m6A modification in watermelon in early responses to CGMMV.
Highlights
Cucumber green mottle mosaic virus (CGMMV) causes substantial global losses in cucurbit crops, especially watermelon
We found that the global m 6A level in resistant watermelon clearly decreased after CGMMV
CGMMV infection decreased the m6A global level in resistant watermelon plants To explore whether m 6A modification responded to CGMMV infection, we assessed the mRNA m6A methylation levels in the control and CGMMV-infected leaves from resistant and susceptible watermelon (R1288 and S1252) by colorimetry (Fig. 1)
Summary
Cucumber green mottle mosaic virus (CGMMV) causes substantial global losses in cucurbit crops, especially watermelon. N6-methyladenosine (m6A) methylation in RNA is one of the most important post-transcriptional modification mechanisms in eukaryotes. It has been shown to have important regulatory functions in some model plants, but there has been no research regarding m6A modifications in watermelon. N6-methyladenosine (m6A) methylation is the most prevalent internal modifier of eukaryote RNA and is widely present. It plays multiple roles in RNA metabolism, including stability and degradation [1], alternative. In Arabidopsis, removal of m6A is catalyzed by m6A demethylases of alkylated. He et al BMC Plant Biol (2021) 21:516. The discovery of methyltransferases and demethylases implies the m6A modification is a reversible and dynamic RNA methylation. Evidence indicates that m6A RNA methylation is highly conserved in plants and involved in multiple developmental and biological processes, such as embryonic development [6, 7], trichome branch development [8–
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