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Open Access Highly Accessed Research article

Genetically altering the expression of neutral trehalase gene affects conidiospore thermotolerance of the entomopathogenic fungus Metarhizium acridum

Yajun Leng1, Guoxiong Peng123, Yueqing Cao123 and Yuxian Xia123*

Author Affiliations

1 Genetic Engineering Research Center, College of Bioengineering, Chongqing University, Chongqing, 400030, China

2 Chongqing Engineering Research Center for Fungal Insecticides, Chongqing, 400030, China

3 Key Lab of Functional Gene and Regulation Technologies under Chongqing Municipal Education Commission, Chongqing, 400030, China

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BMC Microbiology 2011, 11:32  doi:10.1186/1471-2180-11-32

Published: 10 February 2011

Abstract

Background

The entomopathogenic fungus Metarhizium acridum has been used as an important biocontrol agent instead of insecticides for controlling crop pests throughout the world. However, its virulence varies with environmental factors, especially temperature. Neutral trehalase (Ntl) hydrolyzes trehalose, which plays a role in environmental stress response in many organisms, including M. acridum. Demonstration of a relationship between Ntl and thermotolerance or virulence may offer a new strategy for enhancing conidiospore thermotolerance of entomopathogenic fungi through genetic engineering.

Results

We selected four Ntl over-expression and four Ntl RNA interference (RNAi) transformations in which Ntl expression is different. Compared to the wild-type, Ntl mRNA expression was reduced to 35-66% in the RNAi mutants and increased by 2.5-3.5-fold in the over-expression mutants. The RNAi conidiospores exhibited less trehalase activity, accumulated more trehalose, and were much more tolerant of heat stress than the wild-type. The opposite effects were found in conidiospores of over-expression mutants compared to RNAi mutants. Furthermore, virulence was not altered in the two types of mutants compared to the wild type.

Conclusions

Ntl controlled trehalose accumulation in M. acridum by degrading trehalose, and thus affected conidiospore thermotolerance. These results offer a new strategy for enhancing conidiospore thermotolerance of entomopathogenic fungi without affecting virulence.