title: Autophagy induction in tobacco leaves infected by potato virus Y(O) and its putative roles.
abstract: Autophagy plays a critical role in the innate immune response of plants to pathogen infection. In the present study, we examined autophagy induced by potato virus Y ordinary strain (PVY(O)) infection in tobacco (Nicotiana benthamiana). Enzyme-linked immunosorbent assays revealed that the number of virus particles in the plant peaked at 2 weeks post-inoculation and then gradually decreased. Additionally, the amount of virus increased significantly in the 3rd and 4th leaves distal to the inoculated leaf and decreased slightly in the 5th leaf. Within 2 weeks of PVY(O) inoculation, the tobacco leaves showed typical symptoms of Potyvirus inoculation, including mottling, yellowing, a mosaic pattern, and necrotic tissue changes at the inoculated site. Based on an ultrastructural analysis of the PVY(O)-infected tobacco leaves, virus aggregates appeared as longitudinal and transverse arrays and pinwheels, which are typical of Potyvirus inoculation. Moreover, PVY(O) infection caused changes in the number, size, and shape of chloroplasts, whereas the number of plastogranules increased markedly. Furthermore, double-membrane autophagosome-like vacuoles, including electron-dense materials, laminated structures, and cellular organelles, were found. The induction of autophagy after the PVY(O) infection of tobacco leaves was further confirmed by the expression of lipidated microtubule-associated protein 1 light chain 3 (LC3)-II, an autophagy marker and p62, an autophagy adaptor protein. The LC3-II levels increased daily over the 4-week period. Although virus inoculation was performed systemically on the basal leaves of the plants, LC3-II was expressed throughout the leaves and the expression was higher in leaves distal to the inoculated leaf. Moreover, PVY(O) infection caused the activation of stress-activated protein kinases/c-Jun N-terminal kinases. Therefore, PVY(O) infection-induced autophagy was positively correlated with the virus content, suggesting that autophagy induction following PVY(O) infection is involved in the anti-pathogen response of the host.
authors.affiliation: Department of Life Science & BK21-Plus Research Team for Bioactive Control Technology, Chosun University, 309 Pilmundaero, Dong-gu, Gwangju 501-759, South Korea.
authors.forename: Dabin
authors.initials: D
authors.lastname: Choi
authors.affiliation: Department of Life Science & BK21-Plus Research Team for Bioactive Control Technology, Chosun University, 309 Pilmundaero, Dong-gu, Gwangju 501-759, South Korea.
authors.forename: Jaeyoung
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Premedics, School of Medicine, Chosun University, 309 Pilmundaero, Dong-gu, Gwangju 501-759, South Korea. Electronic address: seonh@chosun.ac.kr.
authors.forename: Seonhee
authors.initials: S
authors.lastname: Oh
authors.affiliation: Department of Life Science & BK21-Plus Research Team for Bioactive Control Technology, Chosun University, 309 Pilmundaero, Dong-gu, Gwangju 501-759, South Korea. Electronic address: hscheong@chosun.ac.kr.
authors.forename: Hyunsook
authors.initials: H
authors.lastname: Cheong
mesh_terms: D001343:Autophagy / Q000502:physiology*; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology* / Q000821:virology*; D017863:Potexvirus / Q000502:physiology*; D014026:Nicotiana / Q000166:cytology / Q000502:physiology* / Q000821:virology*; D019562:Viral Load / Q000502:physiology
keywords: Autophagy; Potato virus Y(O); Potyvirus; c-Jun N-terminal kinases