Effect of a chemical analogue of autoinducers of microbial anabiosis on the Ca2+ response of mycelial fungi

Abstract

The microbial alkylhydroxybenzenes (AHB), autoinducers of anabiosis, or d1 factors, participate in stress response of mycelial fungi, as determined from changes in intracellular Ca2+ concentration. By using the genetically modified strain Aspergillus awamori 66A, which produces a recombinant Ca2+-dependent protein aequorin, the dynamics of Ca 2+ was studied in the cytosol of cells exposed to mechanical shock in the presence of the protective doses (0.001-0.01% w/vol) of a chemical AHB analogue, 4-n-hexylresorcinol. Like under stressful conditions, Ca2+ concentration increases in the cell cytosol in response to enhanced AHB level in a growing fungal culture; thus, AHB is perceived by cells as a stress signal. The level of cell response, which was determined from the amplitude of luminescence dependent on the Ca2+ concentration in cytosol was related to the physiological age of the cells and AHB concentration. Micromycete preincubation with AHB was found to protect cells from subsequent stress; this was reflected in the Ca2+ response. The protective AHB effect was manifested as (1) a significant decrease in the amplitude of luminescence and, thus, in Ca2+ accumulation in the cytosol during subsequent mechanical stress (as compared to the control-mechanical stress only); (2) development of the secondary Ca2+ response, which was not observed in the control; (3) a high level of Ca2+ retained in the cytosol for a long time in the presence of AHB (as compared to the control without preincubation with AHB). The mechanisms underlying the AHB effect on the Ca 2+ transport systems are discussed.