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. The scientists also examined "landraces," Native Americans' own domesticated cultivars, some of which are quite old. These too are dominated by domesticated HaFT1.
By comparing the activity of domesticated and wild HaFT1, the scientists learned it is the domesticated version of HaFT1 that lengthens the time period during which flowers grow and mature. This can have a wide variety of effects, from increasing the size of the sunflowers' seed disk to increasing the flowers' total seed mass.
Despite its name, domestic HaFT1 isn't the result of domestication -- its origin likely precedes human cultivation. It is called domestic, because it is the version of HaFT1 that caused traits early Native Americans seem to have preferred as they bred the plants for horticulture. 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.
"Our study is the first to provide both strong functional evidence and strong evolutionary evidence that a particular nucleotide variant in this one gene -- HaFT1 -- was critical for early sunflower domestication," Blackman said.
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. A. thaliana's own FT gene had been removed. Cloning genes in this way can eliminate complicating fact
|Contact: David Bricker|