Developmental and Photoregulation of ThreeNeurospora crassaCarotenogenic Genes during Conidiation Induced by Desiccation

Abstract

Neurospora crassaasexual sporulation (conidiation) is induced by different cues including desiccating aerial environments. Three of the genes that are expressed during this developmental pathway are the albino (al) genes, which encode carotenoid biosynthetic enzymes. If conidiation is induced by nutrient deprivation in liquid culture, two overlappingal-3mRNAs,al-3(m) andal-3(c), are expressed (Arpaiaet al.,1995,Dev. Biol.170,620–635). Here we quantitate accumulation of each of the four albino gene messages,al-1, al-2, al-3(m), andal-3(c), in conidiating wild-type cultures and in cultures of two mutants defective in photoinduced carotenogenesis,wc-1andwc-2.Of the four albino gene transcripts, onlyal-1expression is developmentally regulated in wild-type cultures conidiating in darkness. Expression of all four albino gene transcripts is developmentally regulated in conidiatingwc-1orwc-2cultures. Unlike other albino gene transcripts, expression ofal-3(c) is photoregulated only early in conidiation. Thefldandflmutants are defective in conidiation with development halting at distinct early stages of spore formation. In desiccatedfldandflculturesal-1, al-2,andal-3(m) transcript accumulation is observed to peak early and then decline, whileal-3(c) transcript accumulation increases with time.