Effects of mutations in the GanB/RgsA G protein mediated signalling on the autolysis of Aspergillus nidulans

Abstract

Physiological changes taking place in carbon-starved, autolysing cultures of Aspergillus (Emericella) nidulans strains with mutations in the GanB/RgsA heterotrimeric G protein signalling pathway were studied and compared. Deletion of the ganB, rgsA or both genes did not alter markedly either the autolytic loss of biomass or the extracellular chitinase production. However, they caused a significant decrease in the proteinase formation, which was detected by measuring both extracellular enzyme activity and the transcription of the prtA gene. The deletion mutants also showed significantly higher specific gamma -glutamyltranspeptidase activities than the control strain. Deletion of the rgsA gene affected the glutathione peroxidase and catalase formation, as well as the peroxide content of the cells. The concomitant initiations of cell death and developmental genomic programmes may be interconnected via heterotrimeric G-protein signalling and subsequent changes in intracellular ROS levels in ageing A. nidulans.

Regulation of Autolysis in Aspergillus nidulans

“…Although we did not find any clear-cut connection between autolytic cell wall degradation and proteinase production in carbon-starving A. nidulans cultures [20,21], the elimination of the prtA gene coding for an extracellular proteinase [44] resulted in a statistically significant decrease in the declination of dry cell mass and delay in the disorganization of pellets (Fig. 1) during the early autolytic phase of cultivation (25-75 h; [6]).…”

“…Similar to wild type This study (103±12%) a GanB and FadA signaling pathways had no significant effect on chitinase production [20,21]. b Relative specific activities are shown in parenthesis where no reference is given.…”

“…Most of these markers are not exclusively specific for the autolytic process, e.g., a decreasing viability can be the consequence of another age-related physiological process, autophagy, which also relies on hydrolases and results in vacuolization [14,15], and the utilization of exogenous substrates (e.g., proteins) as energy sources also requires extracellular hydrolases (e.g., proteinases) and may liberate ammonia. In our experiments, we chose dry cell mass declination, hyphal fragmentation (together with the disintegration of pellets quantified by shrinking pellet diameters), and the production of extracellular chitinase to characterize autolytic phenotypes [6,[16][17][18][19][20][21]. All the selected markers are connected to cell wall degradation because cell wall represents high percentage of total dry cell mass of fungal cultures, and its breakage and effective disassembly need extracellular hydrolases including autolysis-related chitinase activity [22][23][24].…”

Extracellular DNA Release Acts as an Antifungal Resistance Mechanism in Mature Aspergillus fumigatus Biofilms

“…Positive bands for seven genes indicate that the eDNA is similar in sequence to genomic DNA. bacterial biofilms (26), and evidence exists for eukaryotes from studies of Aspergillus nidulans showing that autolysis is regulated by chitinase activity (42)(43)(44). It was also recently shown that autolysis is associated with chitinases in A. fumigatus biofilms (39).…”

AtfA bZIP-type transcription factor regulates oxidative and osmotic stress responses in Aspergillus nidulans

“…Only changes with probability levels of P · 5% were regarded as statistically signiWcant Pusztahelyi et al 2006). In RT-PCR measurements, the SD values of CPs determined for each gene and culture conditions tested were always within the range of 0.6-1.5 cycles, which were comparable to those found previously for other A. nidulans genes Molnár et al 2006;Pusztahelyi et al 2006). SDs for ¡ CP values were calculated following the rules for the linear combination of measurements (Barford 1967).…”