CAMP is involved in transcriptional regulation of delta9-desaturase during Histoplasma capsulatum morphogenesis.

We have characterized the promoter region of the delta9-desaturase gene from two different strains of the dimorphic fungus Histoplasma capsulatum. Desaturase transcription is regulated in the two phases of growth: it is transcribed in the yeast phase at 37 degrees C, while it is inactive in the mycelial phase at 25 degrees C. Phase transition can be induced by shifting the temperature from 25 to 37 degrees C or by adding cAMP to the growth medium. We have identified a stress-responsive cis element (STRE) responsive to cyclic AMP (cAMP)-signaling pathway and demonstrated that this element acts in H. capsulatum. We have also identified an element, hereafter called DRE (Desaturase Regulatory Element), present in the promoters of the H. capsulatum and S. cerevisiae delta9-desaturase gene. We show that this element is necessary but not sufficient to regulate transcription of the H. capsulatum delta9-desaturase gene.