Adaptive evolution of the rbcL gene in the genus Rheum (Polygonaceae)

ABSTRACT

Rapid putative radiations of Rheum might be caused by the recent uplifts of the Qinghai–Tibetan Plateau and the quaternary climate oscillations. To better understand the molecular adaptation associated with Rheum radiation, in this study, the adaptive evolution of the chloroplast rbcL gene was analysed using the Phylogenetic Analysis Program. The results showed that two amino acid residues (75F, 203I) were under positive selection. The spatial analysis indicated that the site (75F) was located in the β-sheet of the N-terminal loops involved in subunit interactions in the L8S8 molecule, and the site (203I) was in the α/β-barrel active centre located on the C-terminal domain of the large subunit of Rubisco. These results suggest that potential positive selection in rbcL might have played an important role in the adaption of Rheum species to the extreme environments in Qinghai–Tibetan Plateau regions, and different species lineages might have been subjected to different selective pressures.

KEYWORDS:

• Rheum (Polygonaceae)
• rbcL gene
• branch-specific model
• site-specific model
• positive selection

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the Natural Science Foundation of Guangxi [grant number 2013GXNSFAA019062]; Scientific Innovation Ability and Condition Construction of Guangxi [grant number GKN11217028]; Science Research Foundation of Guangxi Institute of Botany [grant number GZY13016].