A gene for carotene cleavage required for pheromone biosynthesis and carotene regulation in the fungus Phycomyces blakesleeanus

Mating and sexual development in fungi are controlled by molecular mechanisms that are specific for each fungal group. Mating in Phycomyces blakesleeanus and other Mucorales requires pheromones derived from β-carotene. Phycomyces mutants in gene carS accumulate large amounts of β-carotene but do not enter the sexual process. We show that carS encodes a β-carotene-cleaving oxygenase that catalyzes the first step in the biosynthesis of a variety of apocarotenoids, including those that act as pheromones. Therefore carS mutants cannot stimulate their sexual partners, although they respond to them. CarS catalyzes the biosynthesis of a β-ring-containing apocarotenoid that inhibits the activity of the carotenogenic enzyme complex in vegetative cells and provides a feedback regulation for the β-carotene pathway. The carS gene product is a keystone in carotenogenesis and in sexual reproduction.     

Effect of vitamin A and beta carotene supplementation on women's health

A large field trial conducted in Nepal confirmed a beneficial effect of vitamin A and beta carotene supplementation on maternal mortality. Maternal deaths during pregnancy or within 12 weeks of delivery occurred at rates of 704/100,000 pregnancies (51/7241) in women who received a placebo, 426/100,000 pregnancies (33/7747) in women who received a single oral vitamin A supplement per week, and 361/100,000 pregnancies (26/7201) among those who received weekly oral beta carotene. The relative risks of pregnancy-related mortality were 0.60 (95% confidence interval (CI), 0.37-0.97) for vitamin A and 0.51 (95% CI, 0.30-0.86) for beta carotene. Before widespread vitamin A and beta carotene supplementation programs are implemented, further evaluation is required of the possible hazards to women of childbearing age and their offspring. For example, exposure to vitamin A during pregnancy has been linked to fetal malformations and schizophrenia.