AUTHOR=Meng Shuai , Huang Suya , Liu Jinhua , Gai Yunpeng , Li Min , Duan Shuo , Zhang Shuting , Sun Xuepeng , Yang Qi , Wang Yuchun , Xu Kai , Ma Haijie 

TITLE=Histone Methylation Is Required for Virulence, Conidiation, and Multi-Stress Resistance of Alternaria alternata

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.924476

DOI=10.3389/fmicb.2022.924476

ISSN=1664-302X

ABSTRACT=<p>Histone methylation, which is critical for transcriptional regulation and various biological processes in eukaryotes, is a reversible dynamic process regulated by histone methyltransferases (HMTs) and histone demethylases (HDMs). This study determined the function of 5 HMTs (<italic>AaDot1</italic>, <italic>AaHMT1</italic>, <italic>AaHnrnp</italic>, <italic>AaSet1</italic>, and <italic>AaSet2</italic>) and 1 HDMs (<italic>AaGhd2</italic>) in the phytopathogenic fungus <italic>Alternaria alternata</italic> by analyzing targeted gene deletion mutants. The vegetative growth, conidiation, and pathogenicity of ∆<italic>AaSet1</italic> and ∆<italic>AaSet2</italic> were severely inhibited indicating that <italic>AaSet1</italic> and <italic>AaSet2</italic> play critical roles in cell development in <italic>A. alternata</italic>. Multiple stresses analysis revealed that both <italic>AaSet1</italic> and <italic>AaSet2</italic> were involved in the adaptation to cell wall interference agents and osmotic stress. Meanwhile, ∆<italic>AaSet1</italic> and ∆<italic>AaSet2</italic> displayed serious vegetative growth defects in sole carbon source medium, indicating that <italic>AaSet1</italic> and <italic>AaSet2</italic> play an important role in carbon source utilization. In addition, ∆<italic>AaSet2</italic> colony displayed white in color, while the wild-type colony was dark brown, indicating <italic>AaSet2</italic> is an essential gene for melanin biosynthesis in <italic>A. alternata</italic>. <italic>AaSet2</italic> was required for the resistance to oxidative stress. On the other hand, all of ∆<italic>AaDot1</italic>, ∆<italic>AaHMT1</italic>, and ∆<italic>AaGhd2</italic> mutants displayed wild-type phenotype in vegetative growth, multi-stress resistance, pathogenicity, carbon source utilization, and melanin biosynthesis. To explore the regulatory mechanism of <italic>AaSet1</italic> and <italic>AaSet2</italic>, RNA-seq of these mutants and wild-type strain was performed. Phenotypes mentioned above correlated well with the differentially expressed genes in ∆<italic>AaSet1</italic> and ∆<italic>AaSet2</italic> according to the KEGG and GO enrichment results. Overall, our study provides genetic evidence that defines the central role of HMTs and HDMs in the pathological and biological functions of <italic>A. alternata</italic>.</p>