title: A new manganese superoxide dismutase identified from Beauveria bassiana enhances virulence and stress tolerance when overexpressed in the fungal pathogen.
abstract: A superoxide dismutase (SOD) was characterized from Beauveria bassiana, a fungal entomopathogen widely applied to insect control. This 209-aa enzyme (BbSod2) showed no more than 71% sequence identity to other fungal Mn-SODs, sharing all conserved residues with the Mn-SOD family and lacking a mitochondrial signal. The SOD activity of purified BbSod2 was significantly elevated by Mn(2+), suppressed by Cu(2+) and Zn(2+) but inhibited by Fe(3+). Overexpressing the enzyme in a BbSod2-absent B. bassiana strain enhanced its SOD activity (107.2 +/- 6.1 U mg(-1) protein) by 4-10-fold in different transformants analyzed. The best BbSod2-transformed strain with the SOD activity of 1,157.9 +/- 74.7 U mg(-1) was 93% and 61% more tolerant to superoxide-generating menadione in both colony growth (EC(50) = 2.41 +/- 0.03 versus 1.25 +/- 0.01 mM) and conidial germination (EC(50) = 0.89 +/- 0.06 versus 0.55 +/- 0.07 mM), and 23% more tolerant to UV-B irradiation (LD(50) = 0.49 +/- 0.02 versus 0.39 +/- 0.01 J cm(-2)). Its virulence to Spodoptera litura larvae was enhanced by 26% [LT(50) = 4.5 (4.2-4.8) versus 5.7 (5.2-6.4) days]. Our study highlights for the first time that the Mn(2+)-cofactored, cytosolic BbSod2 contributes significantly to the virulence and stress tolerance of B. bassiana and reveals possible means to improving field persistence and efficacy of a fungal formulation by manipulating the antioxidant enzymes of a candidate strain.
authors.affiliation: Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, People's Republic of China.
authors.forename: Xue-Qin
authors.initials: XQ
authors.lastname: Xie
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.forename: Bao-Fu
authors.initials: BF
authors.lastname: Huang
authors.forename: Sheng-Hua
authors.initials: SH
authors.lastname: Ying
authors.forename: Ming-Guang
authors.initials: MG
authors.lastname: Feng
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D052982:Beauveria / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity* / Q000528:radiation effects; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D004269:DNA, Bacterial; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D013172:Spores, Fungal / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D013482:Superoxide Dismutase / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014466:Ultraviolet Rays; D014774:Virulence
chemical_list: D004269:DNA, Bacterial; D013482:Superoxide Dismutase