Early and Late Trisporoids Differentially Regulate β-Carotene Production and Gene Transcript Levels in the Mucoralean Fungi Blakeslea trispora and Mucor mucedo

The multistep cleavage of carotenoids inMucorales during the sexual phase results in a cocktail of trisporic acid (C18 ) sex pheromones. We hypothesized that the C18 trisporoid intermediates have a specific regulatory function for sex pheromone production and carotenogenesis that varies with genus/species and vegetative and sexual phases of their life cycles. Real-time quantitative PCR kinetics determined forBlakeslea trispora displayed a very high transcript turnover in the gene for carotenoid cleavage dioxygenase,tsp3 , during the sexual phase. Anin vivo enzyme assay and chromatographic analysis led to the identification of β-apo-12′-carotenal as the first apocarotenoid involved in trisporic acid biosynthesis inB. trispora . Supplementation of C18 trisporoids, namely D'orenone, methyl trisporate C, and trisporin C, increasedtsp3 transcripts in the plus compared to minus partners. Interestingly, thetsp1 gene, which is involved in trisporic acid biosynthesis, was downregulated compared totsp3 irrespective of asexual or sexual phase. Only the minus partners of bothB. trispora andMucor mucedo had enhanced β-carotene production after treatment with C20 apocarotenoids, 15 different trisporoids, and their analogues. We conclude that the apocarotenoids and trisporoids influence gene transcription and metabolite production, depending upon the fungal strain, corresponding genus, and developmental phase, representing a “chemical dialect” during sexual communication.