Fertile sporophore production of Typhula phacorrhiza in the field is related to temperatures near freezing.
Two field tests and one lab test were conducted to examine the environmental factors affecting sporophore production in Typhula phacorrhiza and to compare these results with those documented for T. ishikariensis and T. incarnata. In the 2001 lab test where lighting, soil moisture, and soil-sand media were tested in 50 mL screw-cap tubes incubated at 4 degrees C, the limiting factor for Typhula sporophore production was found to be moisture. In the fall 2001 field test, 100 sclerotia of six isolates from three Typhula spp. were placed into pots filled with a sand and soil mixture. The pots were monitored weekly, and maximum sporophore production for all six isolates and for watered and unwatered pots was observed at 11 weeks, which was soon after mean daily temperatures fell below 0 degrees C. In the second field test in fall 2003, five isolates of the three species were tested with similar procedures, but peak sporophore production was observed after 6 weeks, and again only after mean daily temperatures fell below 0 degrees C. In the field, sporophore production of T. phacorrhiza seems to require the same environmental cues as those of T. ishikariensis or T. incarnata, namely high moisture and temperatures near freezing.
Ecology and Physiology
The subnivean environment represents a habitat of snow mold fungi where their resources, i.e., living plant tissues, are limited and do not increase. The fungi have adopted two major contrasting life history strategies in terms of resource utilization: facultative snow mold fungi can become abundant even without snow cover, and obligate snow mold fungi require snow cover for activity. Some obligate snow mold fungi particularly ascomycetes share plant tissues with other genotypes of the same species and coexist, while basidiomycetous obligate snow mold fungi often exclude even other genotypes of the same species and monopolize resources by individualism. The duration of snow cover is, of course, critical to snow mold fungi for survival and propagation, but the beginning of persistent snow cover and its end are other important issues. Snow mold fungi developed diverse life history strategies to adapt to the predictability of snow cover, which is typically represented by the germination rate and the size of sclerotia. Snow mold fungi also exhibit diverse metabolic reactions to tolerate freezing stress by producing antifreeze proteins, exhibiting osmophily, and altering fatty acid composition. Some snow mold fungi protect themselves from freezing by colonizing deeper into plant tissues.
A fungal mating type protein that regulates sexual and asexual development contains a POU‐related domain.
The A mating type factor of the fungus Coprinus cinereus regulates essential steps in sexual development. Here we describe features of one of the four specificity genes of the A42 factor. By transformation we show that the gene regulates not only sexual development but also asexual sporulation. DNA sequence analysis shows that the gene beta 1–1, encodes a protein with a DNA binding motif and is thus likely to be a transcription factor. The DNA binding domain is an unusual homeodomain with D replacing the normally invariant N in the recognition helix and apparent absence of helix II. The homeodomain is linked to a helical region related to the POUs domain, which is part of a bipartite DNA binding domain of certain animal transcription factors. Like POU factors, the beta 1–1 protein has regions rich in serine, threonine and proline which are possible transactivation domains. Putative dimerization domains and sites for post‐translational modification are described.