LIGHT AND DEVELOPMENT REGULATE THE EXPRESSION OF THE ALBINO-3 GENE INNEUROSPORA-CRASSA

The albino-3 gene of Neurospora crassa codes for geranylgeranyl pyroph osphate synthase, an enzyme involved in the biosynthesis of carotenoid s. The albino-3 locus encodes two overlapping transcription units that give rise to two mRNAs of 2.2 kb (al-3(c)) and 1.6 kb (al-3(m)), with the promoter of the latter residing in the transcribed region of the former. The 1.6-kb transcript was transiently expressed in the myceliu m after light induction, while the 2.2-kb mRNA appeared in conidiating cultures only, independently of light. Al-3(c) mRNA was enhanced in t he conidiophores and was impaired in mutants blocked at the early stag es of conidiation; al-3(c) therefore represents a conidiation-specific transcript. The al-3(c) mRNA level increased upon illumination with b lue light and fluctuated according to the circadian cycle. (C) 1995 Ac ademic Press, Inc.