EPIGENETIC MODIFICATIONS OF FUNGAL DNA AS A TARGET FOR BIOCONTROL OF EARLY-DIVERGING FUNGAL PATHOGENS

The goals of this project are 1) to evaluate N6-methyladenine (6mA) as a novel biocontrol target for early-diverging fungal pathogens and food-spoilage agents of the subphylum Mucoromycotina using Rhizopus microsporus as a model organism and 2) investigate the role of 6mA in the symbiosis of R. microsporus and its bacterial endosymbiont Mycetohabitans. The motivation for this investigation stems from the distinct epigenomes of early-diverging fungi and the high prevalence of bacterial endosymbionts found within fungi of this group. Unlike most eukaryotic lineages that are enriched in 5-methylcytosine (5mC) DNA modifications, early-diverging fungi such as the Mucoromycotina employ N6-methyladenine (6mA) as the predominant epigenetic modification, similar to bacterial genomes. The paucity of 6mA modifications in the genomes of plants and animals coupled with its significance in early-diverging fungal pathogens and food-spoilage agents make it a promising target for biocontrol strategies. In addition, the shared use of 6mA modifications between fungi in the Mucoromycotina and their bacterial endosymbionts may underlie the molecular basis of these symbioses. To address these hypotheses, I will screen a small-molecule collection for inhibition of the R. microsporus adenine methylation machinery to identify compounds with the potential for controlling R. microsporus as a plant pathogen and post-harvest food spoilage agent. I will also generate genomes and genome-wide methylation data for ~60 R. microsporus strains that both do and do not harbor Mycetohabitans endosymbionts. By comparing the 6mA profiles of the genomes of fungi with and without endosymbionts, I aim to identify candidate symbiosis factors that are regulated by 6mA. I will also generate adenine methyltransferase mutants of Mycetohabitansand assess their ability to reestablish a functional symbiosis with their original host fungus to further test the hypothesis that 6mA is significant to symbiosis maintenance.