Phylogenetic and functional analyses of
N
6
-methyladenosine RNA methylation factors in the wheat scab fungus
Fusarium graminearum
Authors: Kim Hyeonjae , Hu Jianzhong , Kang Hunseung , Kim Wonyong 
Published: December 2023

ABSTRACT

In eukaryotes,
N
6
-methyladenosine (m
6
A) RNA modification plays a crucial role in governing the fate of RNA molecules and has been linked to various developmental processes. However, the phyletic distribution and functions of genetic factors responsible for m
6
A modification remain largely unexplored in fungi. To get insights into the evolution of m
6
A machineries, we reconstructed global phylogenies of potential m
6
A writers, readers, and erasers in fungi. Substantial copy number variations were observed, ranging from up to five m
6
A writers in early-diverging fungi to a single copy in the subphylum Pezizomycotina, which primarily comprises filamentous fungi. To characterize m
6
A factors in a phytopathogenic fungus
Fusarium graminearum
, we generated knockout mutants lacking potential m
6
A factors including the sole m
6
A writer
MTA1
. However, the resulting knockouts did not exhibit any noticeable phenotypic changes during vegetative and sexual growth stages. As obtaining a homozygous knockout lacking
MTA1
was likely hindered by its essential role, we generated
MTA1
-overexpressing strains (
MTA1
-OE). The
MTA1
-OE5 strain showed delayed conidial germination and reduced hyphal branching, suggesting its involvement during vegetative growth. Consistent with these findings, the expression levels of
MTA1
and a potential m
6
A reader
YTH1
were dramatically induced in germinating conidia, followed by the expression of potential m
6
A erasers at later vegetative stages. Several genes including transcription factors, transporters, and various enzymes were found to be significantly upregulated and downregulated in the
MTA1
-OE5 strain. Overall, our study highlights the functional importance of the m
6
A methylation during conidial germination in
F. graminearum
and provides a foundation for future investigations into m
6
A modification sites in filamentous fungi.

IMPORTANCE

N
6
-methyladenosine (m
6
A) RNA methylation is a reversible posttranscriptional modification that regulates RNA function and plays a crucial role in diverse developmental processes. This study addresses the knowledge gap regarding phyletic distribution and functions of m
6
A factors in fungi. The identification of copy number variations among fungal groups enriches our knowledge regarding the evolution of m
6
A machinery in fungi. Functional characterization of m
6
A factors in a phytopathogenic filamentous fungus
Fusarium graminearum
provides insights into the essential role of the m
6
A writer
MTA1
in conidial germination and hyphal branching. The observed effects of overexpressing
MTA1
on fungal growth and gene expression patterns of m
6
A factors throughout the life cycle of
F. graminearum
further underscore the importance of m
6
A modification in conidial germination. Overall, this study significantly advances our understanding of m
6
A modification in fungi, paving the way for future research into its roles in filamentous growth and potential applications in disease control.