Science Finds Key to Autumn's Splendor

Single protein triggers the glories of the season, researchers say

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SATURDAY, Sept. 17, 2005 (HealthDay News) -- Autumn's joyous pageant of red, yellow and gold relies on a single protein, new research reveals.

The protein -- with the less-than-poetic name of FtsH6 -- degrades a second compound that spends most of the year holding tight to the green chlorophyll in leaves. As this compound (called LHCII) slips away, hidden pigments of red and yellow are revealed, explain researchers at Umea Plant Science Center in Sweden.

While LHCII is incredibly small, it is also one of the most abundant plant membrane proteins on earth, and each leaf or blade of grass is so full of the compound that the planet's forests appear as swaths of green from space.

But in temperate climes, deciduous leaves lose that green as the days turn shorter.

The Swedish researchers, in conjunction with a Polish scientist, sought to identify exactly which type of protein-degrading protease molecule breaks down LHCII and causes plants to turn color in autumn.

Reporting in a recent issue of the Proceedings of the National Academy of Sciences, the researchers started on the assumption the molecule belonged to the family of so-called FtsH proteases. They then used genetically modified plants in which various FtsH proteases had already been removed to conduct their study.

One plant variation lacking a key protease, FtsH6, was largely unable to break down LHCII. That suggests FtsH6 is crucial to seasonal chlorophyll removal, the researchers say.

All is not lost in this seasonal cycle, however: Proteins in dying leaves contain important amino acids that trees and other plants recycle, the researchers say. These amino acids are stored all winter in the tree's trunk, branches, roots and stems until next year -- when they are used to help grow new leaves in the spring.

More information

To learn more about how leaves change color, visit the SUNY College of Environmental Science and Forestry.

SOURCE: Swedish Research Council, news release, Sept. 5, 2005

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