Abstract:

Phytochromes, which receive and transmit signals generated by red and far- red light, can regulate a wide range of developmental and physiological responses during plant development. Their PHY-PAS1 domain is critical for tuning spectroscopic properties of the bound bilin and signal transduction and exists in all members of the gymnosperm phytochrome gene family created by gene duplication. Gene duplications can play significant roles in speciation. The PHYP gene occurs from the first gene duplication event, as a single copy. To further test whether PHY-PAS1 domains in PHYP have experienced the same constraint or positive selection during their evolution in distinct gymnosperm species , we assayed the molecular evolution of 31 gymnosperm PHY-PAS1 domain sequences under the branch, site and branch-site models. Most lineages are highly conserved, with w< 1, but 14 lineages evolved under positive selection, with w> 1; among them 13 lineages are of co-generic species. By contrast, such selective pressure is not detected in more distantly related species.

Key words: adaptive evolution, gymnosperm