Stable Expression of the Fungal Effector BEC1019 in Transgenic Barley to Evaluate Host-Pathogen Interactions

Powdery mildews, caused by obligate fungal pathogens, are a major threat to cereal grain production worldwide. Effector proteins secreted by these pathogens suppress or induce host processes to promote nutrient acquisition and colonization. As such, effectors serve as optimal probes to decode host signaling pathways. We are focusing on the interaction of barley with the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh), to address fundamental questions in host resistance and susceptibility. Among ca. 540 predicted secreted effectors, Blumeria effector candidate (BEC) 1019 is a single-copy gene encoding a putative, secreted metalloprotease. BEC1019 is evolutionarily conserved among at least 96 other diverse fungi, including obligate plant pathogens, necrotrophic animal pathogens, and free-living non-pathogens. It was recently reported that BEC1019 suppresses host cell death and enhances Bgh virulence in barley. We postulate that BEC1019 represents an ancient fungal protein family, members of which have evolved to function as effectors in plant and animal hosts. Here we report overexpression of BEC1019 in barley cv. Golden Promise via Agrobacterium-mediated genetic transformation. Transgenic plants were regenerated following selection with hygromycin. Expression levels of BEC1019 gene variants with or without a signal peptide (SP) and an affinity purification tag (HPB tag), and production of homozygous transgenic seed progenies are reported. Transgenic plants are currently analyzed with pull-down assay to determine cellular localization and confirm target interactions.

Supported by the National Science Foundation - Plant Genome grant 13-39348.