Timing der Entwicklung: Die Rolle von SRR1 an der Schnittstelle zwischen zirkadianer Uhr und Blühzeitkontrolle
Zusammenfassung der Projektergebnisse
The aim of this project was to gain further understanding of how SRR1, which is important for prevention of premature flowering in Arabidopsis, is integrated into the molecular network regulating flowering time. We set out to do this by performing a second site suppressor screen, generating novel mutants by treating srr1-1 seeds with EMS to randomly introduce point mutations throughput its genome. Mutant candidates were screened for suppression of the early flowering phenotype of srr1-1, characterized and identified using a combination of PCR-based mapping and a full genome sequencing approach. 12 suppressor candidates were identified in the initial screen. In three of five sequenced candidates, the identity of the casual mutation could be confirmed. Two candidates, ssm136 and ssm67 were further characterized. The ssm136 mutation led to an amino acid change in a ubiquitin E3 ligase. The ssm67 mutant carries an amino acid change in an unknown protein, which we named HOG. This gene appears to have a role in general development and the regulation of flowering via the GA pathway. When setting up the screen, we expected more known clock- and flowering associated genes to be found. Interestingly, no such genes were identified, but genes involved a variety of responses. This might suggest that SRR1 acts as an integrator between flowering and regulatory elements previously unknown to be part of the flowering time network. As SRR1 is involved in the regulation of the circadian clock and preliminary results showed that SRR1 might regulate flowering in concert with the clock Evening Complex (EC) component LUX, interactions between SRR1 and the EC components LUX, ELF3 and ELF4 were probed. It could be confirmed that SRR1 and LUX have an epistatic relationship in regulation of flowering, but ELF3 and ELF4 acts in parallel genetic pathways. No direct interaction could be shown between SRR1 and LUX on the protein level under the tested conditions. SRR1 regulates gene expression of several known downstream targets. To identify further targets and understand how SRR1 acts as an expressional regulator, a ChIP- Seq experiment was set up to precipitate promoter fragments bound by SRR1 or its interaction partners. It was however not possible to precipitate sufficient amounts of DNA to be able to perform a sequencing. Probably, any DNA-binding complex including SRR1 was unstable under tested conditions or there were too many intermediate factors between SRR1 and its targets. The identification of SRR1 protein interaction partners might be necessary to probe this further. Furthermore, through a collaboration within the SPP1530 priority program on flowering time control, we could show cross-species functionality between Arabidopsis and Brassica napus and revealed gene specialization between Bna.SRR1 copies. In summary, this project has revealed further details about how SRR1 is part of flowering time regulation in Arabidopsis and identified novel components of the regulatory network controlling development and flowering.
Projektbezogene Publikationen (Auswahl)
- (2018) On the move through time – a historical review of plant clock research. Plant Biology 21, 13
Johansson M, Köster T
(Siehe online unter https://doi.org/10.1111/plb.12729) - (2019) Different copies of Sensitivity to Red Light Reduced 1 show strong subfunctionalization in Brassica napus. BMC Plant Biology 19, 372
Schiessl SV, Williams N, Specht P, Staiger D and Johansson M
(Siehe online unter https://doi.org/10.1186/s12870-019-1973-x)
