Biomaterial Database

Endogenous timekeepers in photosynthetic organisms. 2001

C H Johnson

Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee 37235, USA. carl.h.johnson@vanderbilt.edu

Circadian and photoperiodic timing mechanisms were first described in photosynthetic organisms. These organisms depend upon sunlight for their energy, so adaptation to daily and seasonal fluctuations in light must have generated a strong selective pressure. Studies of the endogenous timekeepers of photosynthetic organisms provide evidence for both a fitness advantage and for selective pressures involved in early evolution of circadian clocks. Photoperiodic timing mechanisms in plants appear to use their circadian timers as the ruler by which the day/night length is measured. As in animals, the overall clock system in plants appears to be complex; the system includes multiple oscillators, several input pathways, and a myriad of outputs. Genes have now been isolated from plants that are likely to encode components of the central clockwork or at least that act very close to the central mechanism. Genetic and biochemical analyses of the central clockwork of a photosynthetic organism are most highly advanced in cyanobacteria, where a cluster of clock genes and interacting factors have been characterized.

UI	MeSH Term	Description	Entries
D010788	Photosynthesis	The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)	Calvin Cycle,Calvin-Benson Cycle,Calvin-Benson-Bassham Cycle,Carbon Fixation, Photosynthetic,Reductive Pentose Phosphate Cycle,Dark Reactions of Photosynthesis,Calvin Benson Bassham Cycle,Calvin Benson Cycle,Cycle, Calvin,Cycle, Calvin-Benson,Cycle, Calvin-Benson-Bassham,Photosynthesis Dark Reaction,Photosynthesis Dark Reactions,Photosynthetic Carbon Fixation
D010940	Plant Proteins	Proteins found in plants (flowers, herbs, shrubs, trees, etc.). The concept does not include proteins found in vegetables for which PLANT PROTEINS, DIETARY is available.	Plant Protein,Protein, Plant,Proteins, Plant
D002940	Circadian Rhythm	The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli.	Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D017360	Arabidopsis	A plant genus of the family BRASSICACEAE that contains ARABIDOPSIS PROTEINS and MADS DOMAIN PROTEINS. The species A. thaliana is used for experiments in classical plant genetics as well as molecular genetic studies in plant physiology, biochemistry, and development.	Arabidopsis thaliana,Cress, Mouse-ear,A. thaliana,A. thalianas,Arabidopses,Arabidopsis thalianas,Cress, Mouse ear,Cresses, Mouse-ear,Mouse-ear Cress,Mouse-ear Cresses,thaliana, A.,thaliana, Arabidopsis,thalianas, A.
D056890	Eukaryota	One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.	Eukaryotes,Eucarya,Eukarya,Eukaryotas,Eukaryote