Characterization of a candidate effector of wheat yellow rust targeting chloroplast with a novel transit peptide

Andaç, Ayşe
Fungal pathogen, Puccinia striiformis f. sp. trtici, is the causative agent of stripe disease of wheat which causes disruption on wheat yield in many parts of the world. Fungal pathogens secrete effector molecules into host plant cells to suppress host immunity via virulence to colonize plants. Ongoing efforts are being made to identify and characterize effector proteins in many fungal plant pathogens. Nevertheless, the precise biological and biochemical functions of many effectors, such as their trafficking from the pathogen to the host cytoplasm, have yet to be fully understood. In this study, we show that an effector candidate (PstCTE1) of Puccinia striiformis f. sp. tritici localizes to chloroplasts when expressed in planta, although it has no transit signal region that can be detected by widely accepted prediction tools, indicating that it must be carrying a unique localization signal. Moreover, N-terminal tagging has no effect on the chloroplast localization of PstCTE1. It has been also observed the entrance of the effector to the chloroplast even in the presence of an intact signal peptide on the N-terminus of the transit peptide region, a result that supports possible host cell re-entry.