N6‐Methyladenosine mRNA modification regulates transcripts stability associated with cotton fiber elongation

Abstract

SUMMARYN6‐Methyladenosine (m6A) is the most abundant methylation modification in eukaryotic mRNA. The discovery of the dynamic and reversible regulatory mechanism of m6A has greatly promoted the development of m6A‐led epitranscriptomics. However, the characterization of m6A in cotton fiber is still unknown. Here, we reveal the potential link between m6A modification and cotton fiber elongation by parallel m6A‐immunoprecipitation‐sequencing (m6A‐seq) and RNA‐seq analysis of fibers from the short fiber mutants Ligonliness‐2 (Li2) and wild‐type (WT). This study demonstrated a higher level of m6A in the Li2 mutant, with the enrichment of m6A modifications in the stop codon, 3′‐untranslated region and coding sequence regions than in WT cotton. In the correlation analysis between genes containing differential m6A modifications and differentially expressed genes, we identified several genes that could potentially regulate fiber elongation, including cytoskeleton, microtubule binding, cell wall and transcription factors (TFs). We further confirmed that the methylation of m6A affected the mRNA stability of these fiber elongation‐related genes including the TF GhMYB44, which showed the highest expression level in the RNA‐seq data and m6A methylation in the m6A‐seq data. Next, the overexpression of GhMYB44 reduces fiber elongation, whereas the silencing of GhMYB44 produces longer fibers. In summary, these results uncover that m6A methylation regulated the expression of genes related to fiber development by affecting mRNA's stability, ultimately affecting cotton fiber elongation.