Beauveria bassiana produces microsclerotia-like propagules with active peroxisome biogenesis

CARLA HUARTE BONNET; FLAVIA PAIXÃO; EVERTON FERNANDES; NICOLÁS PEDRINI

Congreso; 50th Annual Meeting and Golden Jubilee Celebration of the Society for Invertebrate Pathology; 2017

Entomopathogenic fungi are able to produce several types of propagulessuch as aerial conidia in solid media, or blastospores, submerged conidia andmicro-sclerotia in liquid cultures. Microsclerotia (MS) are usually melanizedcompact hyphal aggregates that are tolerant to dessication. As far as weknow, there are no reports about the production of melanized microsclerotiaby Beauveria bassiana isolates. The aim of this work was to describemicrosclerotial growth in B. bassiana and to start with studies about themolecular and physiological mechanisms implicated in the production ofthese propagules. B. bassiana strain GHA was cultured in complete liquidmedium for 4 days at 26oC in the dark with vigorous agitation (250 rpm).Microsclerotia-like structures were separated by centrifugation andprocessed for microscopy observation and real time qPCR analysis. Underthese culture conditions, B. bassiana was able to produce compact brownishaggregates that were able to germinate and produce viable conidia afterdesiccation. Optical microscope images showed similarity in form, structureand size with microsclerotia reported from other entomopathogens, andstaining with 3,3-diaminobenzidine (DAB) revealed high peroxidase activity.Genes encoding for peroxisome biogenesis factors, named peroxins, showedhigh expression levels (up to 17-fold induction) for Bbpex5, Bbpex7,Bbpex14/17 and Bbpex19 genes in 4 days cultures compared with conidiaused as starting inocula. Additional studies are being carried out to elucidatethe relationship between microsclerotia formation and peroxisomalbiogenesis, as same as stress tolerance, cell surface alterations and virulenceagainst insect hosts.