Transcriptional studies on stress-induced meiosis in the anaerobic gut fungi Pecoramyces ruminantium strain Hef-5

Abstract

This study focused on the presence of a cryptic sexual life cycle of Pecoramyces ruminantium strain Hef-5. This strain of anaerobic gut fungi (AGF) can be found in the rumen of herbivorous animals and is known to enhance plant biomass metabolism via fermentation and saccharation. In all past research, this fungus has been described as strictly asexual; however, this research has been conducted based on the behavior of the organism in its natural habitat. Many other fungal organisms have been described to exhibit cryptic sexual life cycles which may only appear while the organism is under some stress. The presence of a cryptic sexual cycle can be sensed by the expression of core meiotic genes (CMGs). The three CMGs studied are Hop2, required for homologous pairing, Mnd1, required for recombination and nuclear division, and Dmc1, required for dsDNA break repair and homologous pairing. To impart stress on the organism, samples were flushed with oxygen for increasing increments of five minutes up to one hour, two samples for each time frame. The expression of Hop2 came first at the 10-minute mark and continues to be expressed with few discrepancies through the 60 minute time frame. Dmc1 expression begins at the 20-minute mark and stays, also with few discrepancies, through until the 55-minute mark. Mnd1 is the final CMG to be expressed after 25 minutes of oxygen exposure and continues to be expressed through the 60-minute trial. These results indicate that the AGF strain Hef-5 could have a cryptic sexual cycle under these conditions. The negative control showed no expression for any of the three CMGs, supporting the hypothesis. The continuous expression of these CMGs aligns well with the time frame for meiosis I is S. cerevisiae. Future research to expand this includes a full transcriptomic study of Hef-5 as well as the study of additional CMGs involved in other phases of meiosis.