Molecular Bases for Circadian Clocks

A new class of organic nanoparticles (CN-MBE nanoparticles) with a mean diameter of ca. 30−40 nm, which exhibit a strongly enhanced fluorescence emission, were prepared by a simple reprecipitation method. CN-MBE (1-cyano-trans-1,2-bis-(4‘-methylbiphenyl)ethylene) is very weakly fluorescent in solution, but the intensity is increased by almost 700 times in the nanoparticles. Enhanced emission in CN-MBE nanoparticles is attributed to the synergetic effect of intramolecular planarization and J-type aggregate formation (restricted excimer formation) in nanopaticles. On/off fluorescence switching for organic vapor was demonstrated with CN-MBE nanoparticles.

Enhanced Emission and Its Switching in Fluorescent Organic Nanoparticles

The circadian clock is a widespread cellular mechanism that underlies diverse rhythmic functions in organisms from bacteria and fungi, to plants and animals. Intense genetic analysis during recent years has uncovered many of the components and molecular mechanisms comprising these clocks. Although autoregulatory genetic networks are a consistent feature in the design of all clocks, the weight of evidence favours their independent evolutionary origins in different kingdoms.

Time zones: a comparative genetics of circadian clocks.

http://www.lsic.ucla.edu/classes/lifesci/central/mcdb162/MCDB_162/papers_files/Debono%201998.pdf

Natural Variation in a Neuropeptide Y Receptor Homolog Modifies Social Behavior and Food Response in C. elegans

The earth rotates on its axis every 24 h, with the result that any position on the earth's surface alternately faces toward or away from the sun—day and night. That the metabolism, physiology, and behavior of most organisms changes profoundly between day and night is obvious to even the most

/pdf/plant-circadian-rhythms-3xlojkk9d2.pdf

Plant Circadian Rhythms

The threonine-glycine (Thr-Gly) encoding repeat within the clock gene period of Drosophila melanogaster is polymorphic in length. The two major variants (Thr-Gly)17 and (Thr-Gly)20 are distributed as a highly significant latitudinal cline in Europe and North Africa. Thr-Gly length variation from both wild-caught and transgenic individuals is related to the flies' ability to maintain a circadian period at different temperatures. This phenomenon provides a selective explanation for the geographical distribution of Thr-Gly lengths and gives a rare glimpse of the interplay between molecular polymorphism, behavior, population biology, and natural selection.

https://science.sciencemag.org/content/sci/278/5346/2117.full.pdf

Natural variation in a Drosophila clock gene and temperature compensation.

The period gene is a key regulator of biological rhythmicity in Drosophila melanogaster. The central part of the gene encodes a dipeptide Thr-Gly repeat that has been implicated in the evolution of both circadian and ultradian rhythms. We have previously observed that length variation in the repeat follows a latitudinal cline in Europe and North Africa, so we have sought to extend this observation to the southern hemisphere. We observe a parallel cline in Australia for one of the two major length variants and find higher levels of some Thr-Gly length variants, particularly at the tropical latitudes, that are extremely rare in Europe. In addition we examined >40 haplotypes from sub-Saharan Africa and find a very different and far more variable profile of Thr-Gly sequences. Statistical analysis of the periodicity and codon content of the repeat from all three continents reveals a possible mechanism that may explain how the repeat initially arose in the ancestors of the D. melanogaster subgroup of species. Our results further reinforce the view that thermal selection may have contributed to shaping the continental patterns of Thr-Gly variability.

https://www.genetics.org/content/genetics/174/1/465.full.pdf

Lesley A. Sawyer

Papers

Natural variation in a Drosophila clock gene and temperature compensation.

The period Gene Thr-Gly Polymorphism in Australian and African Drosophila melanogaster Populations: Implications for Selection

Evolution and population biology of theperiodgene

melanogaster populations: implications for selection.