Using GFP fusion proteins to screen for the subcellular localization of Phytophthora infestans RXLR effectors in host cells

Samantha Jo Armintrout, The College of Wooster

Abstract

Phytophthora infestans, a plant pathogen that causes the tomato and potato Late Blight, secretes special effector proteins with a conserved RXLR motif that are translocated into the host cells. The function of these effector proteins is largely unknown, so this study screens the nuclear localization of 15 different GFP-RXLR fusion proteins expressed in yeast. Determining the localization can ultimately help to identify proteins important for pathogenesis as well as helping to determine the possible functions that these proteins have in the host cell. Some of the GFP-RXLR proteins were chosen for quantitative analysis based on preliminary images. These RXLR proteins were shown to have lower GFP expression in the nucleus than in the control, but this was only significant in PexRD11 (21-1). This exclusion from the nucleus might indicate that the GFP is being localized elsewhere, and further investigation of the localization and function of this gene could indicate if it is important for the pathogenesis of a plant cell. Examination of these proteins by a Nuclear Export Signal (NES) predictor indicates that PexRD147-3 (36-8), PexRD26 (119-1), and PexRD46 (92-4) all have a potential NES sequence that facilitates export out of the nucleus. This potentially shows that GFP localization assays in yeast can screen and help determine the function of more P. infestans effector proteins.