Differential Roles of Five Fluffy Genes (flbA–flbE) in the Lifecycle In Vitro and In Vivo of the Insect–Pathogenic Fungus Beauveria bassiana

Abstract

The fluffy genes flbA–flbE are well-known players in the upstream developmental activation pathway that activates the key gene brlA of central developmental pathway (CDP) to initiate conidiation in Aspergillus nidulans. Here, we report insignificant roles of their orthologs in radial growth of Beauveria bassiana under normal culture conditions and different stresses although flbA and flbD were involved in respective responses to heat shock and H2O2. Aerial conidiation level was lowered in the deletion mutants of flbB and flbE (~15%) less than of flbA and flbC (~30%), in which the key CDP genes brlA and abaA were repressed consistently during normal incubation. The CDP-controlled blastospore production in submerged cultures mimicking insect hemolymph was abolished in the flbA mutant with brlA and abaA being sharply repressed, and decreased by 55% in the flbC mutant with only abaA being downregulated. The fungal virulence against a model insect was attenuated in the absence of flbA more than of flbC irrespective of normal cuticle infection or cuticle-bypassing infection (intrahemocoel injection). These findings unravel more important role of flbA than of flbC, but null roles of flbB/D/E, in B. bassiana’s insect–pathogenic lifecycle and a scenario distinctive from that in A.nidulans.

The cAMP‐PKA signalling pathway regulates hyphal growth, conidiation, trap morphogenesis, stress tolerance, and autophagy in Arthrobotrys oligospora

“…However, the transcript levels of a few genes involved in the typical central developmental pathway (CDP) in A. nidulans were slightly altered (Figure 3D). Recent studies have shown the differences in sporulation regulation among species (Guo et al, 2021, 2022a, 2022b). In addition, the transcription levels of six genes related to sporulation were different in the four mutants, which may be related to different defective phenotypes.…”

Essential Role of WetA, but No Role of VosA, in Asexual Development, Conidial Maturation and Insect Pathogenicity of Metarhizium robertsii

“…The homologs of fluG and 5 fluffy genes ( flbA – flbE ) as activators of the brlA expression in A. nidulans have proven essential for insect pathogenicity, virulence, and stress tolerance, but nonessential for the brlA activation in B. bassiana ( 35 – 37 ). These studies indicate conserved roles for brlA and abaA in asexual developmental control of hypocrealean insect pathogens, but a distinct scenario for the activation of brlA in B.…”