University of Arkansas, Fayetteville Division of Agriculture
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Abstract

Chitosanase is an enzyme, similar to chitinase, capable of hydrolyzing the β-1,4-linkages between N-acetyl-D-glucosamine and D-glucosamine residues in partially acetylated chitosan polymers found in fungal cell walls. When attacked by pathogenic fungi, many plants exploit this hydrolytic action as a component of a larger post-attack defense response, but these enzymes may also play a role in the initial plant-pathogen interaction via the generation of elicitors resulting from the hydrolysis of fungal cell walls. To gain insight into these mechanisms, a Paenbacillus chitosanase was cloned, sequenced, and modified for plant expression. The modified gene was delivered to tobacco (Nicotiana tabacum L. cv. Xanthine) leaf disks via Agrobacterium tumenfaciensmediated transformation. Whole plants were regenerated from the transformed cells. The putative transformants were tested for transgene integration, transcription, and translation. Confirmed transformants were then screened for enhanced responses to a Rhizoctonia solani cellwall preparation by measuring time-course production of hydrogen peroxide, phenylalanine ammonia lyase, and peroxidase. These compounds play roles at different points in a pathogenesis-related signal transduction pathway and thus allow for an initial assessment of the global defense response. Preliminary data suggest that transgenic tobacco constitutively expressing a Paenbacillus chitosanase may activate pathogenesis-related defense responses more quickly than wild type tobacco.

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