Host-Specific and Homologous Pairs of Effectors Unveil Novel Stromule Induction Factors.

The poplar rust fungus is part of one of the most devastating group of fungi (Pucciniales) and causes important economic losses to the poplar industry. Because is a heteroecious obligate biotroph, its spread depends on its ability to carry out its reproductive cycle through larch and then poplar parasitism. Genomic approaches have identified more than 1,000 candidate secreted effector proteins (CSEPs) from the predicted secretome of that are potentially implicated in the infection process. In this study, we selected CSEP pairs (and one triplet) among CSEP gene families that share high sequence homology but display specific gene expression profiles among the two distinct hosts. We determined their subcellular localization by confocal microscopy through expression in the heterologous plant system . Five out of nine showed partial or complete chloroplastic localization. We also screened for potential protein interactors from larch and poplar by yeast two-hybrid assays. One pair of CSEPs and the triplet shared common interactors, whereas the members of the two other pairs did not have common targets from either host. Finally, stromule induction quantification revealed that two pairs and the triplet of CSEPs induced stromules when transiently expressed in . The use of and knockout lines showed that CSEPs can induce stromules through an -independent mechanism. However, CSEP homologs shared the same impact on stromule induction and contributed to discovering a new stromule induction cascade that can be partially and/or fully independent of . [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.