Traces of early Native Americans — in sunflower genes

Posted: April 5, 2010 at 1:48 am

Story Summary: The Current Biologypaper suggests reality may be a little more complex. FT genes play a role in sensitizing flowering plants to seasons, and their expression is usually triggered by changes in day length. As far as biologists know, all flowering plants have at least one FT gene. Blackman and his colleagues identified four FT genes in sunflower, Helianthus annuus, which are known as HaFT paralogs. Based on the level of divergence between the various HaFTs and the presence of a single FT copy in lettuce, we inferred that one copy became two during a whole genome doubling event that occurred roughly 30 million years ago, Blackman said. The scientists examined each paralogs expression patterns within sunflower, and by strategically cloning variants of the HaFT genes into the model plant Arabidopsis thaliana, discerned the paralogs physiological properties in one anothers presence. One of the paralogs, HaFT3, has lost function and is no longer expressed. HaFT1 isnt produced in the leaves but at the site of HaFT2 and HaFT4s target — the shoot tip and the green bracts that will radiate out from the flower itself. Only two of the 23 wild populations surveyed possess both types of the HaFT1 allele. That is not the case for domesticated sunflower populations, for which the domestic version of HaFT1 completely (or almost completely) dominates. Modern domesticated sunflowers used in farming are homogeneous for domesticated HaFT1. Genetic evidence the scientists collected from a broad survey of domesticated and wild HaFT1 genes suggests domesticated HaFT1 experienced a selective sweep around the time early Native Americans would have begun cultivating sunflower. How HaFT1 was exerting its flower-delaying effects was not clear until the scientists cloned HaFT1, HaFT2 and HaFT4 into Arabidopsis thaliana in different combinations. Domesticated HaFT1 had no impact on flowering in the presence of HaFT2. But HaFT1 did delay A. thaliana flowering in the presence of HaFT4. Rieseberg has dual appointments at IU Bloomington and the University of British Columbia. It was supported with grants from the National Institutes of Health and the National Science Foundation….Read the Full Story

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