title: A virus-induced gene silencing screen identifies a role for Thylakoid Formation1 in Pseudomonas syringae pv tomato symptom development in tomato and Arabidopsis.
abstract: Pseudomonas syringae pv tomato DC3000 (Pst DC3000), which causes disease in tomato (Solanum lycopersicum) and Arabidopsis (Arabidopsis thaliana), produces coronatine (COR), a non-host-specific phytotoxin. COR, which functions as a jasmonate mimic, is required for full virulence of Pst DC3000 and for the induction of chlorosis in host plants. Previous genetic screens based on insensitivity to COR and/or methyl jasmonate identified several potential targets for COR and methyl jasmonate. In this study, we utilized Nicotiana benthamiana and virus-induced gene silencing to individually reduce the expression of over 4,000 genes. The silenced lines of N. benthamiana were then screened for altered responses to purified COR. Using this forward genetics approach, several genes were identified with altered responses to COR. These were designated as ALC (for altered COR response) genes. When silenced, one of the identified genes, ALC1, produced a hypersensitive/necrosis-like phenotype upon COR application in a Coronatine-Insensitive1 (COI1)-dependent manner. To understand the involvement of ALC1 during the Pst DC3000-host interaction, we used the nucleotide sequence of ALC1 and identified its ortholog in Arabidopsis (Thylakoid Formation1 [THF1]) and tomato (SlALC1). In pathogenicity assays performed on Arabidopsis thf1 mutant and SlALC1-silenced tomato plants, Pst DC3000 induced accelerated coalescing necrotic lesions. Furthermore, we showed that COR affects ALC1 localization in chloroplasts in a COI1-dependent manner. In conclusion, our results show that the virus-induced gene silencing-based forward genetic screen has the potential to identify new players in COR signaling and disease-associated necrotic cell death.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Tamding
authors.initials: T
authors.lastname: Wangdi
authors.forename: Srinivasa Rao
authors.initials: SR
authors.lastname: Uppalapati
authors.forename: Satish
authors.initials: S
authors.lastname: Nagaraj
authors.forename: Choong-Min
authors.initials: CM
authors.lastname: Ryu
authors.forename: Carol L
authors.initials: CL
authors.lastname: Bender
authors.forename: Kirankumar S
authors.initials: KS
authors.lastname: Mysore
mesh_terms: D000596:Amino Acids / Q000378:metabolism / Q000633:toxicity; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003517:Cyclopentanes; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D007192:Indenes / Q000378:metabolism / Q000633:toxicity; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D054883:Oxylipins; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D044224:Pseudomonas syringae / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D014026:Nicotiana
chemical_list: D000596:Amino Acids; D029681:Arabidopsis Proteins; C112279:COI1 protein, Arabidopsis; D003517:Cyclopentanes; D007192:Indenes; D008565:Membrane Proteins; D054883:Oxylipins; C512069:THF1 protein, Arabidopsis; C058487:coronatine; C011006:jasmonic acid