Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2015
Publication Date: N/A
Technical Abstract: Phytophthora encodes an unusually large number of glycosyl hydrolases (GH), with many large gene families resulting from duplication events. There are ten copies of GH 12 (cel12) present in Phytophthora sojae. This is the only pathogen endoglucanase family to which plants produce an inhibitory protein termed xyloglucan-specific endoglucanase inhibitor protein (XEGIP). In an effort to genetically dissect the function of ten Phytophthora sojae cel12 endoglucanases, each gene was expressed in tobacco leaves using Agrobacterium infiltration. Expression of three Phytophthora cel12 endoglucanases, designated 12-G, 12-A and 12-I, caused water soaking and tissue collapse between 42-48 hours post infiltration of Nicotiana benthamiana leaves. None of the other Phytophthora cel12s caused macroscopic damage. Protein determinants were mapped using a series of domain swaps. Tissue collapse function was mapped to the exposed amino terminus of the protein and a signal peptide for extracellular transport was required for tissue damage to occur. Peptide infiltration did not elicit a response, and non-enzymatic fusion proteins also lacked tissue collapse functions. Expression levels of hypersensitivity marker genes PR2 and NADPH oxidase were not significantly different after infiltration of the tissue collapse constructs and other constructs. The cel12 amino terminus may confer unique activity on the cell wall substrate.