title: A laccase exclusively expressed by Metarhizium anisopliae during isotropic growth is involved in pigmentation, tolerance to abiotic stresses and virulence.
abstract: Insect pathogenic fungi including Metarhizium anisopliae offer an environmentally friendly alternative to chemical pesticides. However, their use has been limited by their relatively slow killing speed compared to chemicals and low tolerance to abiotic stresses. We report here on a class 1 laccase (MLAC1) that is involved in both virulence and tolerance to environmental stresses. Mlac1 is expressed during isotropic growth (swelling) but not during polarized growth (e.g., germ tubes and hyphae); Mlac1 is therefore expressed exclusively in the later stages of conidiation and in blastospores when M. anisopliae is living as a saprophyte. During infection processes, Mlac1 is also expressed by appressoria (infection structures) on the cuticle surface and hyphal bodies inside the insect haemocoel. Disrupting Mlac1 reduced virulence to caterpillars because of impaired appressoria and delayed post-infection events. It also produced a yellow-conidia phenotype with increased conidial susceptibility to heat shock (45 degrees C for 2h) and UV-B stress. The relationship between M. anisopliae's pigment-synthesis pathway and its adaptation to diverse natural habitats is discussed.
authors.affiliation: University of Maryland, Department of Entomology, 4112 Plant Sciences Building, College Park, MD 20742, USA. wfang1@umd.edu
authors.forename: Weiguo
authors.initials: W
authors.lastname: Fang
authors.forename: Everton K K
authors.initials: EK
authors.lastname: Fernandes
authors.forename: Donald W
authors.initials: DW
authors.lastname: Roberts
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bidochka
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: St Leger
mesh_terms: D000064:Acclimatization; D000595:Amino Acid Sequence; D000818:Animals; D054884:Host-Pathogen Interactions; D007313:Insecta / Q000382:microbiology; D042845:Laccase / Q000378:metabolism*; D052981:Metarhizium / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D008969:Molecular Sequence Data; D010858:Pigmentation; D013172:Spores, Fungal / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity; D013312:Stress, Physiological; D014774:Virulence
chemical_list: D042845:Laccase