The Hog1-like MAPK Mpk3 collaborates with Hog1 in response to heat shock and functions in sustaining the biological control potential of a fungal insect pathogen

Abstract

The mitogen-activated protein kinase (MAPK) Mpk3/MpkC resembles the MAPK Hog1 but does not necessarily function in some filamentous fungi. Here, we compared functions of Mpk3 and Hog1 in Beauveria bassiana, a filamentous fungal insect pathogen, by multi-phenotypic analyses of their single/double deletion mutants. Growth defects of Δmpk3 were moderate on all 14 minimal media with different carbon or nitrogen sources and less severe than those of Δhog1 on most media tested. The double deletion mutant suffered significantly more severe growth defects than those observed in Δmpk3 and Δhog1, suggesting overlapping and collaborative roles of Mpk3 and Hog1 in uptake of six carbon and four nitrogen sources during normal growth. Despite little impact on conidiation capacity, mpk3 deletion slowed down conidial germination as much as hog1 or double deletion. Conidial resistance to UV-B irradiation decreased less in Δmpk3 than in Δhog1 or in the double mutant. The fungal virulence was similarly attenuated for all deletion mutants against Galleria mellonella larvae through normal cuticle infection. Intriguingly, the Δmpk3 mutant displayed null response to high osmolarity and fludioxonil fungicide, to which both Δhog1 and double mutants were hypersensitive and highly resistant, respectively, but it was more sensitive to a 3-h heat shock at 40 °C than Δhog1 during normal incubation. Western blot hybridization demonstrated that Mpk3 could collaborate with Hog1 in response to heat shock rather than to the chemical stresses. Altogether, Mpk3 collaborates with Hog1 only in response to heat shock and functions in sustaining the pest control potential of B. bassiana.

Molecular basis and regulatory mechanisms underlying fungal insecticides' resistance to solar ultraviolet irradiation

“…Among heat‐shock protein (HSP) genes elucidated in B. bassiana , single‐gene deletions of two HSP40 (Ma5 and Mdj1), four HSP70 family members (Lsh1 and Hsp70c/d/e), and one HSF (heat‐shock transcription factor) domain‐containing protein (Skn7) led to 15–33% reductions in conidial UVB resistance 88–91 . The UVB LD 50 estimates were lowered by 16–42% in the disruption mutants of ten genes that function in, upstream or downstream of the MAPK Hog1 pathway required for cellular responses to high osmolarity and other stress cues in B. bassiana 92–97 . Among those, interestingly, Group III histidine kinase (HK3) acting as a signal sensor of fungicidal (fludioxonil) signal contributed much more to the UVB resistance of B. bassiana (41%) 96 than of M. robertsii (only 6%) 98 .…”

Discovery of N-Benzyl-4-(1-bromonaphthalen-2-yl)oxybutan-1-amine as a Potential Antifungal Agent against Sporidia Growth and Teliospore Germination of Sporisorium scitamineum

“…This is consistent with what has been reported in Metarhizium robertsii, 39 S. cerevisiae, 40 and Beauveria bassiana. 41,42 Furthermore, we measured the transcriptional levels of SsHOG1 in wild-type MAT-1 cells following different durations of heat stress. The results showed that exposure of MAT-1 strains to 45 °C for 2 or 5 min did not produce a significant impact on the transcription levels of SsHOG1 compared to those at 28 °C (Figure 1B).…”