The COL1 gene was isolated from Ophiostoma novo-ulmi using the techniques of insertional mutagenesis and plasmid rescue. Sequence analyses suggest that the COL1 gene encodes a unique protein of 826 amino acids with consensus-type RNA-binding domains, most similar to a putative protein from Schizosaccharomyces pombe which resembles the C-terminus of the Saccharomyces cerevisiae U4/U6 splicing factor PRP24. Disruption of the COL1 gene produced the yeast-like col1 mutant. The inability of the mutant to synthesize the COL1 gene product was confirmed by transcript analysis. Transformation of the col1 mutant with the COL1 gene restored the wild phenotype and production of the 4.0-kb mRNA. The results from this study demonstrate that the COL1 RNA-binding protein is associated with filamentous growth in O. novo-ulmi.

The button mushroom, Agaricus bisporus, is a commercially important cultivated filamentous fungus. During the last decade, the button mushroom industry has depended mainly on two strains (or derivatives of these two strains). Using one of these highly successful strains (strain UI) we examined the phenomenon of strain instability, specifically, the production of irreversible sectors. Three "stromatal" and three "fluffy" sectors were compared with a healthy type Ul strain and with a wild-collected isolate. Compost colonization and fruit body morphology were examined. The main objective of this study, however, was to examine the meiotic stability of the sectored phenotype. Single basidiospores were isolated and subjected to a grain bioassay in which the ability to produce sectors was measured. Our results were as follows: (i) basidiospore cultures obtained from a wild-collected isolate showed no tendency to produce sectors; (ii) approximately 5% of the basidiospore cultures obtained from healthy type Ul strains produced irreversible sectors in the grain bioassay; (iii) the five primary sectors examined produced basidiospore cultures, half of which produced normal-looking growth in the grain bioassay and half of which produced some degree of sectoring; and (iv) the one sectored isolate that represented the F2 generation gave ratios similar to the 1:1 ratio observed for the Fl cultures.

1989. The germination of basidiospores from commercial and wild-collected isolates of Agaricus bisporus (= A. brunnescens). Can. J. Microbiol. 35: 492-498. A standard set of conditions yielding highly reproducible germination kinetics for basidiospores of the commercial mushroom Agaricus bisporus is described. Spores of three commercial, one wild-collected, and one intraspecies hybrid were examined. The effects of presence or absence of growing mycelium, temperature, culture media, and spore age are described. Cycloheximide completely blocked basidiospore germination and the incorporation of [3H]leucine into protein, whereas actinomycin D had no effect on germ tube emergence. Furthermore, [3H]uridine is not incorporated into spores before or during germination, neither in the presence nor absence of actinomycin D. Two types of basidiospore dormancy exist for A. bisporus: (i) exogenously dormant spores and (ii) constitutively dormant spores, both of the group I1 type in which protein synthesis precedes RNA synthesis.