CSL encodes a leucine-rich-repeat protein implicated in red/violet light signaling to the circadian clock in Chlamydomonas

Abstract

The green alga Chlamydomonas reinhardtii shows various light responses in behavior and physiology. One such photoresponse is the circadian clock, which can be reset by external light signals to entrain its oscillation to daily environmental cycles. In a previous report, we suggested that a light-induced degradation of the clock protein ROC15 is a trigger to reset the circadian clock in Chlamydomonas. However, light signaling pathways of this process remained unclear. Here, we screened for mutants that show abnormal ROC15 diurnal rhythms, including the light-induced protein degradation at dawn, using a luciferase fusion reporter. In one mutant, ROC15 degradation and phase resetting of the circadian clock by light were impaired. Interestingly, the impairments were observed in response to red and violet light, but not to blue light. We revealed that an uncharacterized gene encoding a protein similar to RAS-signaling-related leucine-rich repeat (LRR) proteins is responsible for the mutant phenotypes. Our results indicate that a previously uncharacterized red/violet light signaling pathway is involved in the phase resetting of circadian clock in Chlamydomonas.

Comprehensive Multiphase NMR—A Powerful Tool to Understand and Monitor Molecular Processes during Biofuel Production

“…However, the restricted diffusion (DE) fraction shows a significant increase in CH 3 at 150 °C (Figure b-5, see blue arrow). When CH 3 is the most dominant peak in a spectrum, it is a clear indicator that the fraction is protein-rich, where the CH 3 intensity arises from methyl-rich amino acid side chains such as valine and leucine. , At 150 °C (vs 125 °C), the CH 3 increases ∼100% on a relative basis, and at the same time, the total material in the biomass distribution in DE fraction (Figure e) increases from 7.6 to 9.8%, suggesting some proteins are brought into this dynamic phase. It is important to stress that as proteins are macromolecules, even when fully dissolved, they will show very slow diffusion; hence, it is likely that this protein increase in the dynamic fraction is also associated with cell lysis and the protein rich fraction either becomes highly swollen or completely dissolved (but remaining in the “restricted diffusion” fraction because of its macromolecular nature).…”

The role of ROC75 as a daytime component of the circadian oscillator in Chlamydomonas reinhardtii

“…In addition to endogenous oscillations, the ROC15 and ROC40 mRNAs show an acute decline after exposure to light [35,38,39]. To investigate this light response in roc75 to light, cells in the late night phase were exposed to light for 1 h. An acute decline in the expression of these mRNAs was observed in the roc75 mutant as well as in the WT strain ( Fig 5A).…”

“…Continuous culture (5 mL, 1-2x10 7 cells) was harvested by centrifugation. Protein extraction and Western blot were carried out as described previously [39].…”

“…Batch HS culture (5 mL, 1-2x10 7 cells) was harvested by centrifugation. RNA extraction and RT-qPCR was carried out as described previously [39]. Data were normalized with respect to the expression level of RCK1.…”

Uncovering the complex cell wall of Neochloris oleoabundans, a promising green microalga

“…The significant increase of this amino acid (p<0.05) could indicate that N. oleoabundans cell walls contain leucine-rich repeat proteins. These proteins are part of a large variety of organisms and are reported to be involved in many developmental processes and responses to biotic and abiotic stress (Diévart et al, 2011;Kinoshita et al, 2017;Liu et al, 2017). Due to the intrinsic limitation of the EZ:faast TM method, we were unable to detect asparagine, glutamine and arginine in the N. oleoabundans cell wall.…”