Overexpression of chimeric chitinase42 enhanced antifungal activity of <i>Trichoderma harzianum</i> against <i>Fusarium graminearum</i>

Abstract

Evidence for the role of chitinases in biocontrol by <em>Trichoderma</em> species has been well documented.Chit42 lacks a chitin–binding domain (ChBD) which is involved in its binding activity to insoluble chitin. The objective of the present study was to enhance antifungal activity of <em>T. harzianum</em> by overexpression of wild type and hybrid forms of Chit42 containing chitin binding domain<em>.</em> To produce chimeric chitinase with improved enzyme activity, the hybrid chitinase was constructed by the adding of ChBD from <em>Rhizopus oligosporus </em>to the C–terminal end of Chit42 cDNA from <em>T. atroviride</em> using SoEing PCR. The recombinant hybrid chitinase (Chit42–ChBD) displayed a 1.56 fold higher chitinase activity than Chit42. This increase suggests that the ChBDmay play a role in helping the enzyme to bind better to the insoluble chitin. Moreover, Chit42–ChBD transformants showed higher antifungal activity towards <em>Fusarium graminearum</em>, the causal agent of Fusarium head blight (FHB) disease in wheat.