Premium
Differentiated functions of Ras1 and Ras2 proteins in regulating the germination, growth, conidiation, multi‐stress tolerance and virulence of B eauveria bassiana
Author(s) -
Xie XueQin,
Guan Yi,
Ying ShengHua,
Feng MingGuang
Publication year - 2013
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2012.02871.x
Subject(s) - conidiation , biology , mutant , virulence , spore germination , wild type , microbiology and biotechnology , beauveria bassiana , fungal protein , germination , biochemistry , gene , botany , biological pest control
Summary Ras 1 and Ras 2 are two distinct Ras GTPases in B eauveria bassiana , an entomopathogenic fungus whose biocontrol potential against insect pests depends largely on virulence and multi‐stress tolerance. The functions of both proteins were characterized for the first time by constructing dominant‐active ( GTP ‐bound) Ras1 G19V and dominant‐negative ( GDP ‐bound) Ras1 D126A and integrating them and normal Ras1 into wild type and Δ Ras2 for a series of phenotypic and transcriptional analyses. The resultant mutants showed gradient changes of multiple phenotypes but little difference in conidial thermotolerance. Expression of Ras1 D126A caused vigorous hyphal growth, severely defective conidiation, and increased tolerances to oxidation, cell wall disturbance, fungicide and UV ‐ A / UV ‐ B irradiations, but affected slightly germination, osmosensitivity and virulence. These phenotypes were antagonistically altered by m Ras1 G19V expressed in either wild type or Δ Ras2 , which was severely defective in conidial germination and hyphal growth and displayed intermediate changes in other mentioned phenotypes between paired mutants expressing Ras1 G19V or Ras1 D126A in wild type and Δ Ras2 . Their growth, UV tolerance or virulence was significantly correlated with cellular response to oxidation or cell wall disturbance. Transcriptional changes of 35 downstream effector genes involved in conidiation and multi‐stress responses also related to most of the phenotypic changes among the mutants. Our findings highlight that Ras 1 and Ras 2 regulate differentially or antagonistically the germination, growth, conidiation, multi‐stress tolerance and virulence of B . bassiana , thereby exerting profound effects on the fungal biocontrol potential.