Chemical biology news from across RSC Publishing.
Instant insight: Nature's fruitful chemistry
11 September 2008
Bernhard Kräutler and Thomas Müller at the University of Innsbruck in Austria explain why the changing colour of autumn leaves could be good news for your health
How green plant pigments disappear in the autumn, when the colours of the leaves of deciduous trees and shrubs change from green to red and yellow, has been a longstanding puzzle. While chlorophyll biosynthesis has been well studied, how chlorophyll breaks down remained a fascinating enigma until about 17 years ago. This lack of basic knowledge is all the more surprising, as chlorophyll metabolism is probably the most visible manifestation of life on Earth. In fact, it is even seen from outer space, and the total annual turnover of chlorophyll has been estimated to involve more than 1000 million tons.
Catabolites formed as fruit and leaves change colour may be valuable nutritional components
But chlorophyll breakdown is not merely a detoxification process for the plant. It has also been associated with recycling of important nutrients, of reduced nitrogen, in particular. In the case of the catabolites, the four chlorophyll nitrogen atoms remain in the known tetrapyrrolic breakdown products and are thus not available for the plant to re-use. Nevertheless, they will eventually become part of more global recycling, possibly involving lower organisms.
Recently, we addressed the puzzle of chlorophyll breakdown in ripening fruit. In freshly ripe apples and pears the very same linear tetrapyrroles were detected as chlorophyll catabolites. In fact, these breakdown products were also identical to the ones found in the de-greening leaves of the pear tree. Accordingly, chlorophyll breakdown appears to take a common pathway in fruit ripening and leaf senescence. As senescence is considered to accompany programmed cell death - yet ripening, commonly, is not - this finding is remarkable indeed.
140 years after Gregor Mendel used de-greening in peas as part of his experiments to establish the laws of inheritance, the basis for his observation is now known to be genetic control of chlorophyll breakdown. While the process may no longer be a total enigma, however, its wide-reaching benefits remain a field ripe for investigation.2
Read more in Bernhard Kräutler's perspective 'Chlorophyll breakdown and chlorophyll catabolites in leaves and fruit' in Photochemical and Photobiological Sciences.
1 B Kräutler et al, Angew. Chem., Int. Ed., 1991, 30, 1315
2 B Kräutler, Photochem. Photobiol. Sci., 2008, DOI: 10.1039/b802356p
Link to journal article
Chlorophyll breakdown and chlorophyll catabolites in leaves and fruit
Bernhard Kräutler, Photochem. Photobiol. Sci., 2008, 7, 1114
Also of interest
In this two-part set the editor has brought together contributions from numerous leading scientific experts providing a compendium of information offering the most up-to-date understanding of the primary processes of photosynthesis.
Martin R Adams
This is the third edition of a widely acclaimed text covering the whole field of modern food microbiology.