Functional analysis of effectors from Blumeria graminis and their effect on the plant microbiome

Abstract: With an expected population of 10 billion by the next century, agricultural production has to increase at the same pace to match such demand. One of the main obstacles to achieving this are the pathogenic microorganisms that reduce food quality and yields every year. Understanding the interactions between these microbes and their hosts is essential for shaping proper control strategies. Phytopathogenic fungi utilize effectors, a class of small and diverse proteins, to interact with and supress the defences of the plants they infect. More recently, interest has been growing in the potential for alternative roles for these proteins, such as the interaction with other microbes in the environment and how they may be used to shape the local microbiome. Here, eight proteins from a family of effector genes produced by Blumeria graminis f.sp. tritici, selected based RNA expression profiles showing increased expression during coinfections, were studied using heterologous protein production. Stable transformation of Pichia pastoris and transient expression in Nicotiana benthamiana through homologous recombination and Agroinfiltration respectively was used to perform assays testing the proteins for antimicrobial and phytotoxic activity. While no phytotoxic effects could be observed, three effectors displayed indications of antifungal activity and one in particular displayed both antifungal and antibacterial potential. Additional verification and optimization of the assays used here should be performed to improve the reliability of the results and potentially allow the protocols to be used for characterization of other effectors of obligate biotrophic plant pathogens.