Neurosporaxanthin (b-apo-4¢-carotenoic acid) biosynthesis has been studied in detail in the fungus Fusarium fujikuroi. The genes and enzymes for this biosynthetic pathway are known until the last enzymatic step, the oxidation of the aldehyde group of its precursor,b-apo-4¢-carotenal. On the basis of sequence homology to Neurospora crassa