There is an interesting paper for those technically-inclined in this week's AAAS Science. It has long been known that flowering that is responsive to the length of day is driven by the balance of red and blue light received by the plant. The relevant receptor molecules are called phytochomes, and have been well typified. The mystery was, however, what these did with the information that they contained.
Skip the next para if you don't want to know the gory details. Sawa et al (Science 318 pp 261-264 10 Oct 2007) look at the gene cascade that is affected by this. Cutting through the detail, what happens is this. Many organisms have an internal time keeper, called the circadian clock. This expresses itself in plants in the rise and fall of a the product of a gene called GI. Another product from a gene called ZTL binds to this, in a way which is stabilised by "blue light" phytochrome. That complex in turn binds to yet another gene product, called TOC1, and marks it for destruction. TOC1, in its turn, controls the production of GI, and so the clock ticks at a rate set by the amount of blue light. However, this is not all of the story, because GI - now entrained to the day length of the moment - also complexes with another product, called FKF1. It also does this in a way which is also enhanced by blue light. The resulting complex marks a protein called CDF1 for destruction, so long days with lots of blue light reduce this compound in the plant. The concentration of CDF1 is absolutely crucial, however, as it represses a gene called CO (also called Constans) which - and here is the Big Message - is the trigger for flowering. Ergo, if a chemical could be produced that represses CO/Constans, then one could force flowering at any time: Cattleyas for Christmas, Spring Melons. This would be a horticultural revolution, for obvious reasons. I assume that the big agrochemical people are already onto this... Also in the same issue is a review of the bar coding movement as it applies to plants. It appears that my earlier remarks were a bit sanguine: it looks like plants will need three and not one gene barcode region to get a proper taxonomic separation. However, the days of the diagnostic dipstick are plainly not far off. There is, perhaps, limited utility in a simple dip stick diagnostic that will tell you that "this is indeed a lion", but a great deal to be said for one that says "this is indeed a V. coerulea, or C. rex" or - with certainty and acrtoss the relvant spectrum - that this is "not a CITES annex 1 species". ______________________________ Oliver Sparrow +44 (0)1628 823187 www.chforum.org _______________________________________________ the OrchidGuide Digest (OGD) [email protected] http://orchidguide.com/mailman/listinfo/orchids_orchidguide.com
