Identifying phenotypic effects in Sporisorium reilianum and Ustilago maydis lacking the alternative oxidase gene.

Ustilago maydis and Sporisorium reilianum are both dimorphic fungi that cause infection in the host plant, corn (Zea mays). In order for infection to be successful, compatible haploid mating types must form a dikaryon that later leads to the development and dispersal of teliospores. In order to sustain growth, energy is produced via the electron transport chain within the mitochondrion. Host plants often produce harsh reactive oxygen species, resulting in the need to use an alternative respiration pathway such as employing an alternative oxidase. Therefore, this study attempted to investigate the role of the aox gene in pathogenicity for these fungi. This was achieved by disrupting the gene of interest and assessing mating, response to stress, and virulence. Virulence was found to be lower in seedlings infected with U. maydis deletion strains, suggesting aox could play a role in pathogenicity. Mating assays and stress tests did not show any differences in growth. Unfortunately, data could not be collected from S. reilianum infections, whose assessment requires full development of infected plants, but further study will investigate virulence and teliospore germination rates. There was a slight difference in mating, but this could not be quantified and should be compared to mating during infection as a future point of investigation. Additionally, there were no differences in morphology or growth ability of deletion strains when compared to wild type during stress tests