Proposed erythritol biosynthetic pathway (15, 33, 37) and the pentaketide pathway for melanin biosynthesis in fungi (25, 42, 43, 44). P, phosphate; CoA, coenzyme A; TCA, tricarboxylic acid; 4HNR, tetrahydroxynaphthalene reductase; 2-HJ, 2-hydroxyjuglone.