Predicting the physiological role of circadian metabolic regulation in the green alga Chlamydomonas reinhardtii.

Although the number of reconstructed metabolic networks is steadily growing, experimental data integration into these networks is still challenging. Based on elementary flux mode analysis, we combine sequence information with metabolic pathway analysis and include, as a novel aspect, circadian regulation. While minimizing the need of assumptions, we are able to predict changes in the metabolic state and can hypothesise on the physiological role of circadian control in nitrogen metabolism of the green alga Chlamydomonas reinhardtii.

The role of an E-box element: multiple frunctions and interacting partners.

Circadian clocks can be entrained by light-dark or temperature cycles. In the green alga Chlamydomonas reinhardtii, 12h changes in temperature between 18°C and 28°C synchronize its clock. Both subunits of the circadian RNA-binding protein CHLAMY1, named C1 and C3, are able to integrate temperature information.

Both subunits of the circadian RNA-binding protein CHLAMY1 can integrate temperature information.

The circadian RNA-binding protein CHLAMY1 from the green alga Chlamydomonas reinhardtii consists of two subunits named C1 and C3. Changes in the C1 level cause arrhythmicity of the phototaxis rhythm, while alterations in the level of C3 lead to acrophase shifts. Thus, CHLAMY1 is involved in maintaining period and phase of the circadian clock.

A heteromeric RNA-binding protein is involved in maintaining acrophase and period of the circadian clock.

The RNA-binding protein CHLAMY1 from the green alga Chlamydomonas reinhardtii consists of two subunits. One (named C1) contains three lysine homology motifs and the other (named C3) has three RNA recognition motifs. CHLAMY1 binds specifically to uridine-guanine-repeat sequences and its circadian-binding activity is controlled at the posttranslational level, presumably by time-dependent formation of protein complexes consisting of C1 and C3 or C1 alone.

Changes in photoreceptor currents and their sensitivity to the chemoeffector tryptone during gamete mating in Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii Dangeard generates photoreceptor currents (PCs) upon light excitation. These currents play a key role in the signal transduction chain for photomotility responses. We have previously found that inhibition of PCs by tryptone occurs only in gametes that display chemotaxis toward this agent, and is not observed in chemotactically insensitive vegetative cells.

Proteomic analysis of the eyespot of Chlamydomonas reinhardtii provides novel insights into its components and tactic movements.

Flagellate green algae have developed a visual system, the eyespot apparatus, which allows the cell to phototax. To further understand the molecular organization of the eyespot apparatus and the phototactic movement that is controlled by light and the circadian clock, a detailed understanding of all components of the eyespot apparatus is needed. We developed a procedure to purify the eyespot apparatus from the green model alga Chlamydomonas reinhardtii.