Oxidative stress and peroxisomal biogenesis in microsclerotia produced by the entomopathogenic fungi Beauveria bassiana and Metarhizium robertsii

MARIANELA SANTANA; CARLA HUARTE BONNET; NICOLAS PEDRINI; FLAVIA RS PAIXÃO,

Congreso; JOINT MEETING OF BIOSCIENCE SOCIETIES. LIII ANNUAL MEETING OF ARGENTINE SOCIETY OF BIOCHEMISTRY AND MOLECULAR BIOLOGY (SAIB); 2017

Insect pathogenic fungi are able to produce resistance structurescalled microsclerotia (MS), which are potential candidates for use inbiological control programs. Although oxidative stress was reportedto be involved in MS differentiation in some plant pathogenic fungi,there is no information available for entomopathogenic fungi.Themain goal of this study was to compare the microsclerotial growthin Beauveria bassiana strain GHA and Metarhizium robertsii strainARSEF 2575, and to characterize the expression pattern of genesinvolved in oxidative stress responses and peroxisomal biogenesis.Fungi were cultured in agitated (250 rpm) complete liquid mediumwith optimal carbon/nitrogen ratio for MS production. Daily aliquotswere collected and examined by both optical and transmission electronmicroscopy (TEM) after staining with the peroxidase activitymarker 3,3-diaminobenzidine (DAB). Samples were also used forqPCR analysis to study the expression pattern of superoxide dismutasegenes (sod), catalase genes (cat), and peroxins (pex) involvedin peroxisome biogenesis. DAB staining showed high peroxidaseactivity in MS for both strains, with lower staining in hypha closeto the borders of the structure. TEM images also showed higherperoxidase activity in mitochondria and peroxisomes. Although pexgenes were induced in both strains, Bbpex7 was more induced inB. bassiana, whereas Mrpex19 showed higher expression levels inM. robertsii. At least one of each oxidative stress marker family wasalso induced in both strains. We conclude that an oxidative stressscenario is triggered in MS producing fungi, including proliferation ofperoxisome-like organelles and high peroxidase activity. More studiesare need to be carried out to elucidate the relationship betweenMS formation, oxidative stress and peroxisomal biogenesis to betterunderstand the similarities and differences found in microsclerotialmetamorphosis of entomopathogenic fungi