Life Keeps Quality Time

Several recent findings describe how living organisms keep accurate time in surprising ways.

Your UV clock:  Stem cells in the skin keep time to protect us from damaging ultraviolet radiation.  “Circadian Rhythms in Skin Stem Cells Protect Us Against UV Rays,” Science Daily announced. A researcher explained, “Our study shows that human skin stem cells posses an internal clock that allows them to very accurately know the time of day and helps them know when it is best to perform the correct function.”  The stem cells “turn on” the UV protection genes.  See also Nature News.

Your birthday clock:  Our genes also keep time in mysterious ways involved in aging, Medical Xpress reported with the headline, “Biological clock able to measure age of most human tissues.”  The timekeeping is apparently an epigenetic phenomenon.  This biological clock does not tick at a constant rate, but changes up to about age 20, when it stabilizes.  A UCLA researcher wants to understand it so that diseases associated with aging can be treated.

RNA regulator:  Current Biology reported a “novel layer of regulation for the clock” in mammals, in the form of micro-RNAs.  Researchers from Florida State described the biological clock thus: “As in other organisms, the timekeeping mechanism in mammals depends on a self-sustaining transcriptional negative feedback loop with a built-in time delay in feedback inhibition.”  The miRNA molecules are responsible for the built-in time delay.

The sugar clock in plants:  According to Science Daily, “Plants use sugars to tell the time of day.”  The sugars are produced in photosynthesis.  The “sugar levels within a plant play a vital role in synchronizing circadian rhythms with its surrounding environment.”  The accumulation of sugar is “a bit like the resetting of a stopwatch,” a researcher at the University of York explained.  Expanding on circadian rhythms generally, the article states,

Plants, like animals, have a 24 hour ‘body-clock’ known as the circadian rhythm. This biological timer gives plants an innate ability to measure time, even when there is no light — they don’t simply respond to sunrise, for example, they know it is coming and adjust their biology accordingly. This ability to keep time provides an important competitive advantage and is vital in biological processes such as flowering, fragrance emission and leaf movement.

Multiple independent clocks:  European researchers were surprised to find additional timekeeping mechanisms in some marine animals that work independently.  The bristle worm, for instance, in addition to the diurnal clock, has a separate clock that tracks the lunar phases (see similar finding about a crustacean in Current Biology).   Nature News described the finding: “Some marine invertebrates have at least two internal clocks, which follow different times and have different mechanisms, according to two new studies,” adding, “Multiple timepieces might prove common among animals.”  National Geographic provided more examples: mice with a 12-hour clock, and marine organisms that watch the tides.  There’s also, of course, the monthly menstrual cycle in women.  The uncanny ability of some crabs, fish, and worms to time their spawning to the moon has fascinated biologists for many years.  Now, researchers are just beginning to understand the mechanisms at the cellular level.

Wasn’t there a story long ago about finding a watch, and considering what it implied?