Structure-Function Analysis of a CVNH-LysM Lectin Expressed during Plant Infection by the Rice Blast Fungus Magnaporthe oryzae

The rice blast fungus Magnaporthe oryzae's genome encodes a hypothetical protein (MGG_03307) containing a type III CVNH lectin, in which a LysM domain is inserted between individual repeats of a single CVNH domain. At present, no structural or ligand binding data are available for any type Ill CVNH and functional studies in natural source organisms are scarce. Here, we report NMR solution structure and functional data on MGG_03307. The structure of the CVNH/LysM module revealed that intact and functionally competent CVNH and LysM domains are present. Using NMR titrations, carbohydrate specificities for both domains were determined, and it was found that each domain behaves as an isolated unit without any interdomain communication. Furthermore, live-cell imaging revealed a predominant localization of MGG_03307 within the appressorium, the specialized fungal cell for gaining entry into rice tissue. Our results suggest that MGG_03307 plays a role in the early stages of plant infection.