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

Abstract

The microbial alkylhydroxybenzenes (AHB), which are anabiosis autoinducers also termed d1 factors, participate in the stress response of mycelial fungi, as determined from changes in intracellular Ca2+ concentration. By using the genetically modified strain Aspergillus awamori 66A, which produces the recombinant Ca2+ -dependent protein aequorin, the dynamics of Ca2+ was studied in the cytosol of cells exposed to mechanical shock in the presence of protective doses (0.001-0.01% w/vol) of a chemical AHB analogue, 4-n-hexylre-sorcinol. As under stressful conditions, Ca2+ concentration increases in the cell cytosol in response to an 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 the cytosol, was related to the physiological age of the cells and the 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 a secondary Ca2+ response, which was not observed in the control; and (3) a high level of Ca 2+ 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 Ca2+ transport systems are discussed. © 2004 MAIK "Nauka/Interperiodica".