FIG 1.

Intermediates and products of the ergot alkaloid pathway (as composited from branches found in different fungi). The role of different alleles of easA (isomerase versus reductase encoding types) in controlling the branch point is indicated. Alkaloids with a 9,10 double bond (e.g., setoclavine and lysergic acid and its derivatives) often occur as diastereoisomers at position 8. Roles for enzymes discussed in the text or with genes illustrated in Fig. 2 are indicated near arrows. Double arrows indicate one or more omitted intermediates. The inset shows ring and position labeling referred to in the text. DMAPP, dimethylallylpyrophosphate.