Taxonomic group: fungi / Ascomycota
(Phylum: Ascomycota)
Organ / tissue: cell wall
The structure was elucidated in this paperNCBI PubMed ID: 29802184Publication DOI: 10.1128/AEM.01086-18Journal NLM ID: 7605801Publisher: American Society for Microbiology
Correspondence: Luo Z <luozb1
163.com>; Keyhani NO <keyhani
ufl.edu>, Zhang T <ztongbing
163.com>; Liu P <chenqy528428520
sina.com>; Bai Y <lpfswu
163.com>; Chen Q <baiyt_swu
163.com>; Zhang Y <yjzhang
swu.edu.cn>
Institutions: Academy of Agricultural Sciences, Southwest University, Chongqing, China, Biotechnology Research Center, Southwest University, Chongqing, China, Department of Microbiology and Cell Science, University of Florida, Gainesville, USA
Fungal β-1,3-glucanosyltransferases are cell wall-remodeling enzymes implicated in stress response, cell wall integrity, and virulence, with most fungal genomes containing multiple members. The insect-pathogenic fungus Beauveria bassiana displays robust growth over a wide pH range (pH 4 to 10). A random insertion mutant library screening for increased sensitivity to alkaline (pH 10) growth conditions resulted in the identification and mapping of a mutant to a β-1,3-glucanosyltransferase gene (Bbgas3). Bbgas3 expression was pH dependent and regulated by the PacC transcription factor, which activates genes in response to neutral/alkaline growth conditions. Targeted gene knockout of Bbgas3 resulted in reduced growth under alkaline conditions, with only minor effects of increased sensitivity to cell wall stress (Congo red and calcofluor white) and no significant effects on fungal sensitivity to oxidative or osmotic stress. The cell walls of ΔBbgas3 aerial conidia were thinner than those of the wild-type and complemented strains in response to alkaline conditions, and β-1,3-glucan antibody and lectin staining revealed alterations in cell surface carbohydrate epitopes. The ΔBbgas3 mutant displayed alterations in cell wall chitin and carbohydrate content in response to alkaline pH. Insect bioassays revealed impaired virulence for the ΔBbgas3 mutant depending upon the pH of the media on which the conidia were grown and harvested. Unexpectedly, a decreased median lethal time to kill (LT50, i.e., increased virulence) was seen for the mutant using intrahemocoel injection assays using conidia grown at acidic pH (5.6). These data show that BbGas3 acts as a pH-responsive cell wall-remodeling enzyme involved in resistance to extreme pH (>9).IMPORTANCE Little is known about adaptations required for growth at high (>9) pH. Here, we show that a specific fungal membrane-remodeling β-1,3-glucanosyltransferase gene (Bbgas3) regulated by the pH-responsive PacC transcription factor forms a critical aspect of the ability of the insect-pathogenic fungus Beauveria bassiana to grow at extreme pH. The loss of Bbgas3 resulted in a unique decreased ability to grow at high pH, with little to no effects seen with respect to other stress conditions, i.e., cell wall integrity and osmotic and oxidative stress. However, pH-dependent alternations in cell wall properties and virulence were noted for the ΔBbgas3 mutant. These data provide a mechanistic insight into the importance of the specific cell wall structure required to stabilize the cell at high pH and link it to the PacC/Pal/Rim pH-sensing and regulatory system.
β-1, filamentous fungi, Beauveria bassiana, cell wall integrity, alkaline tolerance, high pH, 3-glycanosyltransferase
Structure type: structural motif or average structure
Location inside paper: p. 3, Introduction
Trivial name: chitin
Compound class: cell wall polysaccharide, glucan, cell wall polisaccharide
Contained glycoepitopes: IEDB_135813,IEDB_137340,IEDB_141807,IEDB_151531,IEDB_153212,IEDB_241099,IEDB_423114,IEDB_423150,SB_74,SB_85
Methods: PCR, biological assays, genetic methods, extraction, antibody binding, binding assays, confocal microscopy, phenol-sulfuric acid assay, TEM, centrifugation, hydrolysis
Related record ID(s): 48634, 48636, 48650, 48651, 48652, 48689, 48691, 48694, 48715, 48752, 48757, 48764, 48769, 48785, 48794, 48796, 48801, 48804, 48828, 48853, 48859, 48872, 48900, 48901, 48902, 48984
NCBI Taxonomy refs (TaxIDs): 176275Reference(s) to other database(s): GTC:G97099AY
Show glycosyltransferases
There is only one chemically distinct structure:
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