() and the Circadian Control of Stomatal Aperture.

The endogenous circadian (∼24 h) system allows plants to anticipate and adapt to daily environmental changes. Stomatal aperture is one of the many processes under circadian control; stomatal opening and closing occurs under constant conditions, even in the absence of environmental cues. To understand the significance of circadian-mediated anticipation in stomatal opening, we have generated (specifically guard cell) Arabidopsis () plants in which the oscillator gene () was overexpressed under the control of the guard-cell-specific promoter, The plants showed a loss of ability to open stomata in anticipation of daily dark-to-light changes and of circadian-mediated stomatal opening in constant light.

The use of fluorescent proteins to analyze circadian rhythms.

Compared with luciferase which is widely used as a reporter for circadian rhythms in Arabidopsis thaliana, available fluorescent markers are generally too stable to allow circadian oscillations to be measured. However, we have developed a technique to use the nuclear localization of circadian-controlled transcription factors fused to a fluorescent reporter as a means of measuring circadian rhythms. This technique has the advantage of being suitable for analyzing rhythms at the level of individual cells and in living plants.

Cell autonomous and cell-type specific circadian rhythms in Arabidopsis.

The circadian system of plants regulates a wide range of rhythmic physiological and cellular output processes with a period of about 24 h. The rhythms are generated by an oscillator mechanism that, in Arabidopsis, consists of interlocking feedback loops of several components including CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION 1 (TOC1) and CCA1 HIKING EXPEDITION (CHE). Over recent years, researchers have gained a detailed picture of the clock mechanism at the resolution of the whole plant and several tissue types, but little information is known about the specificities of the clock mechanism at the level of individual cells.

Disruption of Nap14, a plastid-localized non-intrinsic ABC protein in Arabidopsis thaliana results in the over-accumulation of transition metals and in aberrant chloroplast structures.

Chloroplasts are the major sink for Fe in shoot tissues because of the requirements of the photosynthetic process and to storage in ferritins. Such requirements are common both to plastids and to their evolutionary progenitors, the cyanobacteria. Here, we examined whether iron transport mechanisms were conserved throughout the evolution of photosynthetic organisms.

Over-expression of CONSTANS-LIKE 5 can induce flowering in short-day grown Arabidopsis.

To ensure that the initiation of flowering occurs at the correct time of year, plants need to integrate a diverse range of external and internal signals. In Arabidopsis, the photoperiodic flowering pathway is controlled by a set of regulators that include CONSTANS (CO). In addition, Arabidopsis plants also have a family of genes with homologies to CO known as CO-LIKE (COL) about which relatively little is known.

Posttranslational regulation of CIRCADIAN CLOCK ASSOCIATED1 in the circadian oscillator of Arabidopsis.

As an adaptation to life in a world with predictable daily changes, most eukaryotes and some prokaryotes have endogenous circadian (approximately 24 h) clocks. In plants, the circadian clock regulates a diverse range of cellular and physiological events from gene expression and protein phosphorylation to cellular calcium oscillations, hypocotyl growth, leaf movements, and photoperiod-dependent flowering. In Arabidopsis (Arabidopsis thaliana), as in other model organisms, such as Drosophila (Drosophila melanogaster) and mice, circadian rhythms are generated by molecular oscillators that consist of interlocking feedback loops involving a number of elements.

CIRCADIAN CLOCK ASSOCIATED1 transcript stability and the entrainment of the circadian clock in Arabidopsis.

The circadian clock is an endogenous mechanism that generates rhythms with an approximately 24-h period and enables plants to predict and adapt to daily and seasonal changes in their environment. These rhythms are generated by molecular oscillators that in Arabidopsis (Arabidopsis thaliana) have been shown to consist of interlocking feedback loops involving a number of elements. An important characteristic of circadian oscillators is that they can be entrained by daily environmental changes in light and temperature.

Mutations in CHLOROPLAST RNA BINDING provide evidence for the involvement of the chloroplast in the regulation of the circadian clock in Arabidopsis.

The Arabidopsis circadian system regulates the expression of up to 36% of the nuclear genome, including many genes that encode photosynthetic proteins. The expression of nuclear-encoded photosynthesis genes is also regulated by signals from the chloroplasts, a process known as retrograde signaling. We have identified CHLOROPLAST RNA BINDING (CRB), a putative RNA-binding protein, and have shown that it is important for the proper functioning of the chloroplast.