The endochitinase VDECH from Verticillium dahliae inhibits spore germination and activates plant defense responses

Chitinases function in the digestion of chitin molecules, which are present principally in insects and fungi. In plants, chitinase genes play important roles in defense, and their expression can be triggered in response to both biotic and abiotic stresses. In this study, we cloned and characterized an endochitinase (VDECH) from Verticillium dahliae, strain Vd080. The VDECH coding region consists of 1845 bp with two exons and one 54 by intron, encoding a 615 amino acid protein with the predicted molecular weight (MW) of 63.9 kDa. The VDECH cDNA without signal peptide-encoding region was introduced into pCold-TF vector and the recombinant protein HIS-VDECH with a predicted MW of 114 kDa was expressed. HIS-VDECH showed high tolerance to extreme temperature, exhibiting efficient chitinolytic activity at 50 degrees C. In addition, VDECH triggered typical plant defense responses, including a hypersensitive response, oxidative burst, and elicited increased expression of defense-related genes in both Arabidopsis and cotton. VDECH-treatment of the conidial spores of V. dahliae and Fusarium oxysporum resulted in marked reductions in the germination of these spores in both fungi. After 36 h of incubation with VDECH, the inhibition rate of germination was recorded at 99.57% for V. dahliae, and 96.89% for F. oxysporum. These results provide evidence that VDECH is recognized by the plant to elicit defense responses, and also that VDECH is an effective inhibitor of conidia germination, both of which may be exploited for disease control. (C) 2017 Elsevier B.V. All rights reserved.