"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. "One of those copies proliferated further through two small-scale duplications that we infer occurred much more recently."
The scientists examined each paralog's 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 another's presence.
One of the paralogs, HaFT3, has lost function and is no longer expressed. Countless genome surveys show "non-functionalization" is a common fate for gene duplicates in plants and other eukaryotes, possibly because the extra dose of genetic expression can be wasteful or overtly harmful to the organism.
Two of the paralogs, HaFT2 and HaFT4, are structurally similar to each other and have retained normal function. The proteins they encode are produced in leaves in response to day length. It is believed the HaFT2 and HaFT4 proteins travel down to the stem and up to the shoot tip, where they compel meristem cells to develop into flower buds, but this has yet to be shown conclusively for Helianthus annuus.
HaFT1 isn't produced in the leaves but at the site of HaFT2 and HaFT4's target -- the shoot tip and the green bracts that will radiate out from the flower itself. There are two basic versions of the HaFT1 called alleles. The domesticated HaFT1 allele is distinguished from the wild allele by the omission of a single nucleotide. But what a difference that nucleo
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