Clustering of spore-specific genes in Aspergillus nidulans.

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Abstract
The chromosomal organization of genes that are expressed specifically in the asexual spores (conidia) of A. nidulans was investigated, using 2 experimental approaches. In the first, 30 different recombinant clones, containing long nuclear DNA inserts and at least 1 spore-specific gene, were selected randomly. The total number of spore-specific genes present in each clone was then determined by RNA blot analysis. In the 2nd approach, several chromosomal recombinant DNA libraries, having average insert lengths ranging 1-15 kilobases, were constructed. The fraction of clones in each library having one or more spore-specific poly(A)+ RNA-coding regions was then determined by colony or plaque filter hybridization with radiolabeled, spore-specific, complementary DNA. The results from these experiments were compared to statistical predictions based on the assumption that the spore-specific genes are randomly distributed in the Aspergillus genome. In both cases, the experimental values deviated significantly from the predicted values, demonstrating that the spore-specific genes are nonrandomly arranged in the genome. Rather, they apparently occur frequently in tightly linked clusters.