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Applied and Environmental Microbiology, January 2007, p. 295-302, Vol. 73, No. 1
0099-2240/07/$08.00+0     doi:10.1128/AEM.01974-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Increased Insect Virulence in Beauveria bassiana Strains Overexpressing an Engineered Chitinase{triangledown}

Yanhua Fan,1,{dagger} Weiguo Fang,1,2,{dagger} Shujuan Guo,1 Xiaoqiong Pei,1 Yongjun Zhang,1 Yuehua Xiao,1 Demou Li,1 Kai Jin,1 Michael J. Bidochka,2 and Yan Pei1*

Biotechnology Research Center, Southwest University, Beibei, Chongqing, People's Republic of China,1 Department of Biological Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario, Canada L2S 3A12

Received 19 August 2006/ Accepted 25 October 2006

Entomopathogenic fungi are currently being used for the control of several insect pests as alternatives or supplements to chemical insecticides. Improvements in virulence and speed of kill can be achieved by understanding the mechanisms of fungal pathogenesis and genetically modifying targeted genes, thus improving the commercial efficacy of these biocontrol agents. Entomopathogenic fungi, such as Beauveria bassiana, penetrate the insect cuticle utilizing a plethora of hydrolytic enzymes, including chitinases, which are important virulence factors. Two chitinases (Bbchit1 and Bbchit2) have previously been characterized in B. bassiana, neither of which possesses chitin-binding domains. Here we report the construction and characterization of several B. bassiana hybrid chitinases where the chitinase Bbchit1 was fused to chitin-binding domains derived from plant, bacterial, or insect sources. A hybrid chitinase containing the chitin-binding domain (BmChBD) from the silkworm Bombyx mori chitinase fused to Bbchit1 showed the greatest ability to bind to chitin compared to other hybrid chitinases. This hybrid chitinase gene (Bbchit1-BmChBD) was then placed under the control of a fungal constitutive promoter (gpd-Bbchit1-BmChBD) and transformed into B. bassiana. Insect bioassays showed a 23% reduction in time to death in the transformant compared to the wild-type fungus. This transformant also showed greater virulence than another construct (gpd-Bbchit1) with the same constitutive promoter but lacking the chitin-binding domain. We utilized a strategy where genetic components of the host insect can be incorporated into the fungal pathogen in order to increase host cuticle penetration ability.

* Corresponding author. Mailing address: Biotechnology Research Center, Southwest University, Beibei, Chongqing, People's Republic of China. Phone: 86-23-68251883. Fax: 86-23-68250515. E-mail: peiyan3{at}swu.edu.cn.

{triangledown} Published ahead of print on 3 November 2006.

{dagger} These authors contributed equally to this paper.

Applied and Environmental Microbiology, January 2007, p. 295-302, Vol. 73, No. 1
0099-2240/07/$08.00+0     doi:10.1128/AEM.01974-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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