HOMOLOGY AT THE AMINO-ACID LEVEL BETWEEN PLANT PHYTOCHROMES AND A REGULATOR OF ASEXUAL SPORULATION IN EMERICELLA (=ASPERGILLUS) NIDULANS

Protein sequence comparison between the N-terminal regions of the BRLA (bristle A) protein of the ascomycete fungus Aspergillus nidulans and a number of plant phytochromes has demonstrated a moderate level. of sequence similarity. The region of similarity corresponds to the phyto chrome domains believed to be responsible for photoreception and which undergo light-induced conformational changes, although a putative chr omophore-binding site is not evident. Over 22% of residues are conserv ed and 24% conservatively substituted between residues 1 and 272 of BR LA and the N-terminal domains of Type 1 phytochromes from dicotyledono us species. A lower level of similarity, but over the same region, is observed in comparison with a wider range of phytochromes. Given the k nown role of BRLA as a transcriptional activator involved in conidiati on, and the red/far-red reversible photoregulation of this development al process, the similarity with phytochromes may be significant.