Increased virulence of transgenic Trichoderma koningi strains to the Asian corn borer larvae by overexpressing heterologous chit42 gene with chitin-binding domains

Abstract

The chit42 gene cloned from Metarhizium anisopliae lacks chitin-binding domain (chBD), which plays important roles in binding insoluble chitin. Five kinds of hybrid chitinase Trichoderma transformants were constructed in this study, where the chit42 gene was fused to chBDs derived from plant, bacterial, and insect sources. The transformant Mc4 harboring chBDs from bitter melon (Momordica charantia) displayed the highest chitinase activity among all chBDs. The chitinase activities of Mc4, chit42 Trichoderma transformant Mchit3, and wild-type strain T30 were 44.94, 32.48, and 12.38 U/mL, respectively. The mortality rate of corn borer larvae in Mc4 fermentation liquid treatment increased by 10% and 30% compared with Mchit3 and T30, respectively. The midgut microvilli and goblet cell microvilli of the corn borer larvae exhibited distinct pathological changes after 48 h of feeding in Mc4 treatment. Mc4 also exhibited the strongest antifungal activity against Fusarium verticillioides and Rhizoctonia solani.

Keywords:

• Chit42
• Trichoderma koningi
• Metarhizium anisopliae
• chBD
• hybrid chitinase
• Asian corn borer larvae

Acknowledgments

This research was supported by the China Agriculture Research System (CARS-02), the “948” project of the Ministy of Agriculture of China (2011-G4), the key project from Shanghai Municipal Science and Technology Commission (09391910900) and the National Department Public Benefit Research Foundation of China (No. 200903052). We would also thank Dr. Wang Zhenying for providing us with many batches of artificially cultured the Asian corn borer larvae.