Expression and promoter characterization of BbPacC, a pH response transcription factor gene of the entomopathogenic fungus Beauveria bassiana

Abstract

To survive, the entomopathogenic fungus Beauveria bassiana, which shows promise as a biocontrol agent for a variety of pests, including agricultural and forestry pests and vectors of human pathogens, must tailor gene expression to the particular pH of its environment. The pH response transcription factor gene BbPacC and its flanking sequence were cloned from this fungus. Quantitative reverse transcription (RT)-PCR revealed that it is highly induced by alkaline pH and salt stress, and the expression level achieved twice that of the housekeeping gene c-actin. A microfluorometric assay indicated that the 1479 bp promoter region could activate the expression of enhanced green fluorescent protein (EGFP) under the same conditions. Truncation analysis showed that the 1479, 1274, 1040, 888 and 742 bp promoters have similar efficiencies in activating expression of b-glucuronidase (GUS). The GUS activities of corresponding transformants reached approximately 50 % that of those containing the strong constitutive promoter PtrpC. A truncation upstream at the -572 bp position (referenced to the translation start codon ATG), however, resulted in a significant loss of GUS activity. Both the upstream absences of the "502 and "387 bp positions caused almost complete loss of GUS activity. These results suggest that PPacC is an efficient, alkaline, and salt-inducible promoter, the core cis-elements are mainly located within the -742 to -502 bp region, and promoters equal to or longer than 742 bp may be feasible for regulating gene expression in response to an ambient pH or salt stress.

Refining the pH response in Aspergillus nidulans: a modulatory triad involving PacX, a novel zinc binuclear cluster protein

“…Many pacC/RIM101 homologues, like A. nidulans pacC [(Tilburn et al ., ) and Figs and B], are preferentially expressed under neutral to alkaline conditions. These include those of: Beauveria bassiana (Zhou et al ., ), C. albicans (Bensen et al ., ), F. oxysporum (Caracuel et al ., ), Magnaporthe oryzae (Landraud et al ., ), Metarhizium robertsii (Huang et al ., ), Trichoderma harzianum (Moreno‐Mateos et al ., ), T. virens (Trushina et al ., ), Wangiella ( Exophial ) dermatitidis (Wang and Szaniszlo, ), Y. lipolytica (Lambert et al ., ) but not, curiously, S. cerevisiae (Lamb et al ., ; Serrano et al ., ; Lamb and Mitchell, ; Viladevall et al ., ). This suggests that autoregulation might be a common feature, but the absence of reporter studies precludes determining whether this would be positive or negative.…”

The PacC transcription factor regulates secondary metabolite production and stress response, but has only minor effects on virulence in the insect pathogenic fungus Beauveria bassiana

“…The M. robertsii pacC homologue has been shown to regulate pH dependent growth, sporulation, and virulence (Huang et al ., ). Expression of the B. bassiana pac C is regulated by ambient pH, with induction at alkaline pH (>8.0) as well as in response to salt stress (Zhou et al ., ). Here we show that the B. bassiana PacC transcription factor is important for growth, stress response at alkaline pH, contributes to conidial UV‐resistance, and is linked to both activation and repression of different secondary metabolite biosynthetic pathways.…”

Activation of Ustilaginoidin Biosynthesis Gene uvpks1 in Villosiclava virens Albino Strain LN02 Influences Development, Stress Responses, and Inhibition of Rice Seed Germination

“…The pathogenic fungi were capable of living in an environment with a wide pH range. While living in symbiosis with plants, the rhizospheric environment is mostly neutral or acidic, which is beneficial for fungal secondary metabolism and infection [56][57][58][59][60][61]. In this study, the growth of the albino strain LN02 was more strongly inhibited with a pH of 5.5 than that of the P1 strain or uvpks1 Cstrain 1 (Figure 4).…”