Secreted Effector Proteins of Poplar Leaf Spot and Stem Canker Pathogen Manipulate Plant Immunity and Contribute to Virulence in Diverse Ways.

Fungal effectors play critical roles in manipulating plant immune responses and promoting colonization. is a heterothallic ascomycete fungus that causes Septoria leaf spot and stem canker disease in poplar ( spp.) plantations. This disease can result in premature defoliation, branch and stem breakage, increased mortality, and plantation failure. However, little is known about the interaction between and poplar. Previous work predicted 142 candidate secreted effector proteins in (SmCSEPs), 19 of which were selected for further functional characterization in this study. SmCSEP3 induced plant cell death in , while 8 out of 19 tested SmCSEPs suppressed cell death. The signal peptides of these eight SmCSEPs exhibited secretory activity in a yeast signal sequence trap assay. Confocal microscopy revealed that four of these eight SmCSEPs target both the cytoplasm and the nucleus, whereas four predominantly localize to discrete punctate structures. Pathogen challenge assays in demonstrated that the transient expression of six SmCSEPs promoted infection. The expression of these six genes were induced during infection. SmCSEP2, SmCSEP13, and SmCSEP25 suppressed chitin-triggered reactive oxygen species burst and callose deposition in . The candidate secreted effector proteins of target multiple compartments in the plant cell and modulate different pattern-triggered immunity pathways. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 "No Rights Reserved" license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.