The ELF4 gene controls circadian rhythms and flowering time in Arabidopsis thaliana

Abstract

Many plants use day length as an environmental cue to ensure proper timing of the switch from vegetative to reproductive growth. Day-length sensing involves an interaction between the relative length of day and night, and endogenous rhythms that are controlled by the plant circadian clock. Thus, plants with defects in circadian regulation cannot properly regulate the timing of the floral transition. Here we describe the gene EARLY FLOWERING 4 (ELF4), which is involved in photoperiod perception and circadian regulation. ELF4 promotes clock accuracy and is required for sustained rhythms in the absence of daily light/dark cycles. elf4 mutants show attenuated expression of CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), a gene that is thought to function as a central oscillator component. In addition, elf4 plants transiently show output rhythms with highly variable period lengths before becoming arrhythmic. Mutations in elf4 result in early flowering in non-inductive photoperiods, which is probably caused by elevated amounts of CONSTANS (CO), a gene that promotes floral induction.

ELF4Is Required for Oscillatory Properties of the Circadian Clock

“…It was noted that, after transfer to constant conditions following exposure to LD cycles, elf4-1 mutant plants displayed weak rhythmicity on the first day (Doyle et al, 2002). This could mean that the oscillator was, upon transfer to constant conditions, running down rather than stopping instantly.…”

“…We have shown previously that ELF4 is expressed in the evening and that the elf4 loss-of-function mutant has low CCA1 expression leading to arrest of the elf4 oscillator after one cycle under free run (Doyle et al, 2002). Recently, it was shown that elf4 also has low LHY transcript levels, implicating ELF4 in a feedback loop with CCA1 and LHY (Kikis et al, 2005).…”

“…Further, it has been interpreted that ELF4 controls red-light repression of hypocotyl elongation (Khanna et al, 2003) and that ELF4, together with TOC1, plays a major role in phytochrome-mediated input to the clock (Kikis et al, 2005). The early flowering behavior of elf4 is accompanied by misregulation of the flowering activator CONSTANS (CO), implying ELF4 acts on flowering time by regulating expression of CO (Doyle et al, 2002). Connecting ELF4's action on the clock to downstream red-light perception is required to understand the pleiotropic nature of the elf4 mutations.…”

“…Previously, we identified early flowering4 (elf4) from Arabidopsis and showed that ELF4 is important for circadian precision and normal clock function (Doyle et al, 2002). The elf4 loss-of-function mutation attenuated free-running rhythmicity in all clock outputs tested and this included components believed to make up the central clock machinery (Doyle et al, 2002;Kikis et al, 2005; this article).…”

“…The elf4 loss-of-function mutation attenuated free-running rhythmicity in all clock outputs tested and this included components believed to make up the central clock machinery (Doyle et al, 2002;Kikis et al, 2005; this article). Circadian specificity of ELF4 within the clock was only partially defined with these studies.…”