PT  - JOURNAL ARTICLE
AU  - Muhammad Usman Anwer
AU  - Amanda Davis
AU  - Seth Jon Davis
AU  - Marcel Quint
TI  - Photoperiod sensing of the circadian clock is controlled by ELF3 and GI
AID  - 10.1101/321794
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 321794
4099  - http://biorxiv.org/content/early/2018/05/14/321794.short
4100  - http://biorxiv.org/content/early/2018/05/14/321794.full
AB  - ELF3 and GI are two important components of the Arabidopsis circadian clock. They are not only essential for the oscillator function but are also pivotal in mediating light inputs to the oscillator. Lack of either results in a defective oscillator causing severely compromised output pathways, such as photoperiodic flowering and hypocotyl elongation. Although single loss of function mutants of ELF3 and GI have been well-studied, their genetic interaction remains unclear. We generated an elf3 gi double mutant to study their genetic relationship in clock-controlled growth and phase transition phenotypes. We found that ELF3 and GI repress growth during the night and the day, respectively. We also provide evidence that ELF3, for which so far only a growth inhibitory role has been reported, can also act as a growth promoter under certain conditions. Finally, circadian clock assays revealed that ELF3 and GI are essential Zeitnehmers that enable the oscillator to synchronize the endogenous cellular mechanisms to external environmental signals. In their absence, the circadian oscillator fails to synchronize to the light-dark cycles even under diurnal conditions. Consequently, clock-mediated photoperiod-responsive growth and development is completely lost in plants lacking both genes, suggesting that ELF3 and GI together convey photoperiod sensing to the central oscillator. Since ELF3 and GI are conserved across flowering plants and represent important breeding and domestication targets, our data highlight the possibility of developing photoperiod-insensitive crops by manipulating the combination of these two key genes.One sentence summary ELF3 and GI are essential for circadian clock mediated photoperiod sensing.Author Contributions M.U.A., S.J.D. and M.Q. conceived the project. M.U.A. and A.D. performed the experiments. M.U.A. wrote the article with contributions of all authors.Funding information The funding for this work was provided by a Biotechnology and Biological Sciences Research Council grant to SJD (BBSRC grant code BB/N018540/1), a grant by the Deutsche Forschungsgemeinschaft to MQ (Qu 141/6–1), and the Leibniz Association.