Magnaporthe oryzae encoded effector protein AvrPi54 interacts in vivo with rice encoded cognate resistance protein Pi54 at the host plasma membrane

Plant pathogens deliver effector proteins which enter plant cells in order to establish the disease. The resistance (R) proteins in the plants can recognize some of these effectors and initiate a race-specific resistance response. These effectors which aid in triggering defense signaling in host upon R-protein mediated recognition are termed as Avirulence (Avr) proteins. AvrPi54 is an Avr protein from an ascomycete fungus, Magnaporthe oryzae, which causes hypersensitive response in rice cells containing broad-spectrum R-gene, Pi54. In this study, we have analysed several characteristics of AvrPi54 protein computationally and studied its subcellular localization in presence and absence of Pi54 protein. Our results suggest AvrPi54 is a small hydrophobic protein with no significant homology with any known proteins available in any publicly available database, till date. Transient expression of eYFP fused AvrPi54 protein (AvrPi54-eYFP) in epidermis of onion bulb suggested its translocation to nucleus and plasma membrane. Further, Bimolecular fluorescence complementation (BiFC) assay in the tobacco leaf cells depicted that Pi54 and AvrPi54 proteins interact at plasma membrane. Based on the obtained evidences, we infer that AvrPi54 probably is functional in nucleus of rice cells, either as a transcription factor or as a chromatin remodeler, thus playing important role in immunocompromization of the host. However, presence of Pi54 protein in the host cell might restrict the trespass of AvrPi54 into the nucleus by interacting directly with it at the plasma membrane and thus eliciting defense response.