Silencing of AtRAP, a target gene of a bacteria-induced small RNA, triggers antibacterial defense responses through activation of LSU2 and down-regulation of GLK1

• Published in: The New phytologist Vol. 215; no. 3; pp. 1144 - 1155
• Main Authors: Wang, Huan, Seo, Jang‐Kyun, Gao, Shang, Cui, Xinping, Jin, Hailing
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01-08-2017; Wiley Subscription Services, Inc
• Subjects: Anti-Bacterial Agents - metabolism; Antiinfectives and antibacterials; Arabidopsis - genetics; Arabidopsis - immunology; Arabidopsis - microbiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; AtRAP; Bacteria; Bacterial infections; Chloroplasts; Disease Resistance; DNA microarrays; Down-Regulation; Gene Expression Regulation, Plant; Gene Knockout Techniques; Gene Silencing; Genes, Plant; GLK1; glk1 glk2; Immunity; Infections; Lines; LSU2; Mutation - genetics; Nucleic acids; Pathogens; plant defense; Plant Diseases - genetics; Plant Diseases - microbiology; Plant immunity; Plants (botany); Protein Binding; Proteins; Pseudomonas; Pseudomonas syringae - physiology; Reactive Oxygen Species - metabolism; Ribonucleic acid; RNA; RNA, Plant - genetics; RNA-binding protein; RNA-Binding Proteins; siRNA; Sulfur; Sulphur; Tomatoes; Transcription; Transcription Factors; glk1 glk2; GLK1; plant defense; AtRAP; LSU2
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14654

Plants fine-tune their sophisticated immunity systems in response to pathogen infections. We previously showed that AtlsiRNA-1, a bacteria-induced plant endogenous small interfering RNA, silences the AtRAP gene, which encodes a putative RNA binding protein.
In this study, we demonstrate that AtRAP functions as a negative regulator in plant immunity by characterizing molecular and biological responses of the knockout mutant and overexpression lines of AtRAP upon bacterial infection.
AtRAP is localized in chloroplasts and physically interacts with Low Sulfur Upregulated 2 (LSU2), which positively regulates plant defense. Our results suggest that AtRAP negatively regulates defense responses by suppressing LSU2 through physical interaction. We also detected downregulation of the transcription factor GOLDEN2-LIKE 1 (GLK1) in atrap-1 using microarray analysis. The glk1 glk2 double mutant showed enhanced resistance to Pseudomonas syringae pv. tomato, which is consistent with a previous study showing enhanced resistance of a glk1 glk2 double mutant to Hyaloperonospora arabidopsidis.
Taken together, our data suggest that silencing of AtRAP by AtlsiRNA-1 upon bacterial infection triggers defense responses through regulation of LSU2 and GLK1.