Phase-Specific Circadian Clock Regulatory Elements in Arabidopsis

Abstract

We have defined a minimal Arabidopsis CATALASE 3 (CAT3) promoter sufficient to drive evening-specific circadian transcription of a LUCIFERASE reporter gene. Deletion analysis and site-directed mutagenesis reveal a circadian response element, the evening element (EE: AAAATATCT), that is necessary for evening-specific transcription. The EE differs only by a single base pair from the CIRCADIAN CLOCK ASSOCIATED 1-binding site (CBS: AAAAAATCT), which is important for morning-specific transcription. We tested the hypothesis that the EE and the CBS specify circadian phase by site-directed mutagenesis to convert the CAT3 EE into a CBS. Changing the CAT3 EE to a CBS changes the phase of peak transcription from the evening to the morning in continuous dark and in light-dark cycles, consistent with the specification of phase by the single base pair that distinguishes these elements. However, rhythmicity of the CBS-containing CAT3 promoter is dramatically compromised in continuous light. Thus, we conclude that additional information normally provided in the context of a morning-specific promoter is necessary for full circadian activity of the CBS.The circadian clock enables an organism to specifically partition aspects of its biology to precise times over the day (Dunlap, 1999). Although the circadian clock is, by definition, endogenous and continues to run in the absence of external time cues, environmental stimuli such as light and temperature act to entrain the internal processes of an organism both to the exact external daily period and in a defined relationship, or phase angle, to the diurnal cycle. For example, in Arabidopsis, light and temperature information are integrated to partition physiological activities such as circadian-regulated leaf movement, stomatal opening, and gene expression to distinct times of day or phases (McClung et al., 2002).A central theme that has emerged in circadian biology is that the core oscillator is composed of a negative feedback loop grounded in positive and negative transcriptional regulation (Dunlap, 1999). It has recently been demonstrated that the Arabidopsis circadian clock entails such a transcriptional feedback loop (Alabadí et al., 2001) that includes at least three components: TIMING OF CAB EXPRESSION 1 (TOC1; also called Arabidopsis PSEUDO-RESPONSE REGULATOR 1, APRR1; Millar et al., 1995;, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1; Wang and Tobin, 1998), and LATE ELON-GATED HYPOCOTYL (LHY; Schaffer et al., 1998).CCA1 and LHY are single-Myb domain transcription factors, and DNA-binding activity of CCA1 to a CCA1-binding site (CBS: AAAAATCT) has been characterized (Wang et al., 1997). The hypothesized role of TOC1 as a transcription factor is based on similarity to CONSTANS, although DNA binding by TOC1 has not been experimentally established (Strayer et al., 2000). However, TOC1 (APRR1) has been shown to bind to PHYTOCHROME-INTERACTING FACTOR 3 (PIF3), a Myc-related basic helix-loop-helix transcription factor, and to the related PIF3-LIKE 1 (PIL1; Makino et al., 2002). Expression o...

Type II protein arginine methyltransferase 5 (PRMT5) is required for circadian period determination in Arabidopsis thaliana

“…We screened an EMS-mutagenized M2 population of seedlings carrying pCAT3:LUC, which exhibits dusk-peaking expression (25), using seedlings entrained to LD cycles and released into DD, and we identified a long-period mutant, prmt5-54 (H54). In DD, Columbia 3 (Col-3) seedlings had a period (± SEM) of 24.7 ± 0.1 h (n = 11), whereas H54 seedlings had a period of 26.9 ± 0.1 h (n = 12; significant by two-tailed t test at P < 0.0001) ( Fig.…”

“…The rhythm in Catalase3 (CAT3) mRNA abundance also dampens in the dark, albeit to high constitutive expression (24). However, expression of a transcriptional fusion of LUC to the Catalase 3 promoter (pCAT3:LUC) maintains strong rhythms in continuous dark (DD), and the period does not lengthen compared with LL (25), in contrast to the rapid dampening and period lengthening of pCAB2:LUC in DD (26). Accordingly, we screened an ethylmethanesulfonate (EMS)-mutagenized population of seedlings expressing a pCAT3:LUC construct for altered period in DD.…”

A zinc knuckle protein that negatively controls morning-specific growth in Arabidopsis thaliana

“…S9D). CAT3 cycles under all diurnal and circadian conditions and may play a role in senescence and stress responses (28,29). Two additional genes of note were down-regulated in TZP-OX: PW9 (encoding a MATH/TRAF domain protein) and one of the PLUS3 homologs that encodes also a SWI/SNF domain ( Fig.…”

Differential expression and phylogenetic analysis suggest specialization of plastid-localized members of the PHT4 phosphate transporter family for photosynthetic and heterotrophic tissues

“…This expression pattern did not persist in LL suggesting that the pattern in LD is related to exposure of the shoot tissues to light rather than circadian control. pattern, two copies of the CIRCADIAN CLOCK ASSOCIATED 1-binding site (CBS: AAAAATCT), which is important for morningspecific circadian expression, 25,26 are located in the PHT4;1 promoter. One CBS is located -17 bp relative to the translation start, and the other is located -281 bp and is on the complementary strand.…”