TEMPERATURE-RELATED EXPRESSION OF THE VACUOLAR ASPARTIC PROTEINASE (APR1) GENE AND BETA-N-ACETYLGLUCOSAMINIDASE (HEX1) GENE DURING CANDIDA-ALBICANS MORPHOGENESIS

Expression of the Candina albicans vacuolar aspartic proteinase (APR1) and beta-N-acetylglucosaminidase (HEX1) genes was studied when carbon -starved cells of strains ATCC 10261 and A72 were induced to grow as y east or as germ tube-forming cells. Amounts of APR1 mRNA were similar under yeast or germ tube growth conditions. However, more APR1 mRNA wa s present in cells grown at 28 degrees C than in cells grown at 37 deg rees C. The Apr1 enzyme activity of cell-free extracts was not affecte d by cellular morphology, culture pH or growth temperature. Amounts of HEX1 mRNA were also higher in N-acetylglucosamine (GlcNAc)-induced ce lls grown at 28 degrees C than in cells grown at 37 degrees C. There w as slightly more HEX1 mRNA in cells grown at pH 4.5 than in cells grow n at pH 6.7. The beta-N-acetylglucosaminidase activities of GlcNAc-gro wn cells correlated with the amounts of HEX1 mRNA and were higher when cells were grown at a lower temperature and at a lower pH Although a similar temperature- and pH-dependent pattern of HEX1 mRNA expression was seen in cells grown on glucose, the enzyme activities in cell-free extracts were all very low. These data indicate that the APR1 and HEX 1, genes play no direct role in the dimorphic transition of C. albican s and that transcription of both genes appears to be temperature regul ated when the cells are released from carbon starvation. The expressio n of HEX1 mRNA is in part under the control of culture pH and translat ion of HEX1 mRNA seems to be regulated by glucose.