Interaktion zwischen dem circadianen System und pflanzlichen Immunantworten bei Arabidopsis thaliana
Zusammenfassung der Projektergebnisse
The project focused on the interconnection between two key regulatory systems in plants: The circadian clock system serves to optimally align plant physiology to the periodic changes of light and darkness in the environment and by these means contributes to fitness of the plant. The innate immune system provides strategies for the plant to combat invading pathogens. In particular we have focussed on the impact of the circadian clock on plant immune responses, using the pathogen associated molecular pattern flg22 and the well established interaction between Pseudomonas syringae and Arabidopsis thaliana as a model. We have shown that in Arabidopsis thaliana the magnitude of a series of immune responses elicited by the pathogen-associated molecular pattern flg22, by virulent and by avirulent Pseudomonas syringae strains depend on the time-of-day of inoculation. Specifically, we have shown for the first time that the oxidative burst is stronger when flg22 is infiltrated in the morning in wild type plants, but not in the arrhythmic phytoclock1 mutant and thus is controlled by the clock. Furthermore, we have shown for the first time that the cell death associates with the hypersensitive response is under clock control. Similarly, when bacteria are syringe-infiltrated into the leaf, defense gene induction is higher and bacterial growth is suppressed more strongly upon morning inoculation in wild type but not in pcl1 plants. These results were similar to those reported by Bhardwaj and colleagues (Bhardwaj et al. 2011) but contrasted with results reported by Shin and colleagues (Shin et al. 2012) that found stronger suppression of bacterial growth upon infection in the evening. By systematically investigating this we found that the clock effect depends on the mode of infection: Upon spray-inoculation onto the leaf surface, defense gene induction is higher and bacterial growth is suppressed more strongly upon evening inoculation. Furthermore, we have found that this different phasing of pre-invasive and post-invasive defense by the circadian clock relates to clock-regulated stomatal movement. In particular, we show that the clock component TIME OF COFFEE may impact pathogen defense via clock-regulated stomatal movement apart from its known role in time-of-day-dependent jasmonate responses. Furthermore, in collaboration with Prof. James R. Alfano we have investigated the role of the circadian clock regulated RNA-binding protein in plant immunity. Plants overexpressing At-GRP7 display enhanced immune reactions. Specifically, flg22-triggered oxidative burst and callose deposition are enhanced in independent AtGRP7-ox plants. Furthermore, the growth of virulent Pst DC3000 bacteria is suppressed more strongly in AtGRP7-ox plants than in wt plants. Moreover, AtGRP7-ox plants show a stronger hypersensitive response (HR) in response to avirulent Pst avrRpt2. The immunity phenotypes depend on the presence of a conserved arginine residue within the RNA-binding domain. In line with this, we have shown that AtGRP7 binds to defence-related genes in vivo.
Projektbezogene Publikationen (Auswahl)
- 2011. Structure function analysis of an ADP-ribosyltransferase type III effector and its RNA-binding target in plant immunity. Journal of Biological Chemistry 286, 43272-43281
Jeong B-R, Lin Y, Joe A, Guo M, Korneli C, Yang H, Wang P, Yu M, Cerny RL, Staiger D, Alfano JR, Xu Y
- 2013. Emerging role for RNA-based regulation in plant immunity. New Phytologist 197, 394-404
Staiger D, Korneli C, Lummer M, Navarro L
(Siehe online unter https://doi.org/10.1111/nph.12022) - 2013. Pseudomonas HopU1 affects interaction of plant immune receptor mRNAs to the RNA-binding protein GRP7. The EMBO Journal 32, 701-712
Nicaise V, Joe A, Jeong B, Korneli C, Boutrot F, Wested I, Staiger D, Alfano JR, Zipfel C
- 2013. The circadian clock goes genomic. Genome Biology 14, 208
Staiger D, Shin J, Johansson M, Davis SJ
(Siehe online unter https://doi.org/10.1186/gb-2013-14-6-208) - (2014) Differential Control Of Pre-Invasive And Post- Invasive Antibacterial Defense By The Arabidopsis Circadian Clock. Plant and Cell Physiology, Volume 55, Issue 9, Pages 1613–1622
Korneli C, Danisman S, Staiger D
(Siehe online unter https://doi.org/10.1093/pcp/pcu092) - 2014. Salicylic acid-dependent and -independent impact of an RNA-binding protein on plant immunity. Plant, Cell & Environment 37, 696-706
Hackmann C, Korneli C, Kutyniok M, Köster T, Wiedenlübbert M, Müller C, Staiger D
(Siehe online unter https://doi.org/10.1111/pce.12188)
