THE STREPTOMYCES-AUREOFACIENS HOMOLOG OF THE WHIB GENE IS ESSENTIAL FOR SPORULATION - ITS EXPRESSION CORRELATES WITH THE DEVELOPMENTAL STAGE

In previous experiments, a Streptomyces aureofaciens gene highly simil ar to the sporulation-specific whiB gene of Streptomyces coelicolor wa s identified. By integrative transformation, via double cross-over, a stable null mutant of the whiB-homologous gene of S. aureofaciens was obtained. The disruption blocked differentiation at a stage between th e formation of aerial mycelium and the development of mature spores, p roducing white aerial hyphae without septation. Expression of the whiB gene was investigated during differentiation by S1 nuclease mapping, using RNA prepared from S. aureofaciens in various developmental stage s. Two putative promoters were identified upstream of the whiB coding region. The stronger promoter, whiB-P2, was induced at the beginning o f aerial mycelium formation, and the weaker promoter, whiB-P1, was exp ressed fairly constantly during differentiation. No differences in the expression of the whiB promoters were detected in an rpoZ-disrupted S . aureofaciens strain. The promoter bearing DNA fragment was inserted into the promoter-probe vector pARC1 to produce an expression pattern consistent with the results of direct RNA analysis.