Evolution of the telomere-associated protein POT1a in arabidopsis thaliana is characterized by positive selection to reinforce protein-protein interaction

Mark A Beilstein, Kyle B. Renfrew, Xiangyu Song, Eugene V. Shakirov, Michael J. Zanis, Dorothy E. Shippen

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Gene duplication is a major driving force in genome evolution. Here, we explore the nature and origin of the POT1 gene duplication in Arabidopsis thaliana. Protection of Telomeres (POT1) is a conserved multifunctional protein that modulates telomerase activity and its engagement with telomeres. Arabidopsis thaliana encodes two divergent POT1 paralogs termed AtPOT1a and AtPOT1b. AtPOT1a positively regulates telomerase activity, whereas AtPOT1b is proposed to negatively regulate telomerase and promote chromosome end protection. Phylogenetic analysis uncovered two independent POT1 duplication events in the plant kingdom, including one at the base of Brassicaceae. Tests for positive selection implemented in PAML revealed that the Brassicaceae POT1a lineage experienced positive selection postduplication and identified three amino acid residues with signatures of positive selection. A sensitive and quantitative genetic complementation assay was developed to assess POT1a function in A. thaliana. The assay showed that AtPOT1a is functionally distinct from single-copy POT1 genes in other plants. Moreover, for two of the sites with a strong signature of positive selection, substitutions that swap the amino acids in AtPOT1a for residues found in AtPOT1b dramatically compromised AtPOT1a function in vivo. In vitro-binding studies demonstrated that all three sites under positive selection specifically enhance the AtPOT1a interaction with CTC1, a core component of the highly conserved CST (CTC1/STN1/TEN1) telomere protein complex. Our results reveal a molecular mechanism for the role of these positively selected sites in AtPOT1a. The data also provide an important empirical example to refine theories of duplicate gene retention, as the outcome of positive selection here appears to be reinforcement of an ancestral function, rather than neofunctionalization. We propose that this outcome may not be unusual when the duplicated protein is a component of a multisubunit complex whose function is in part specified by other members.

Original languageEnglish (US)
Pages (from-to)1329-1341
Number of pages13
JournalMolecular Biology and Evolution
Volume32
Issue number5
DOIs
StatePublished - May 1 2015

Fingerprint

telomerase
Telomerase
telomeres
Telomere
protein-protein interactions
Arabidopsis
Brassicaceae
Gene Duplication
Arabidopsis thaliana
gene duplication
protein
Duplicate Genes
genetic complementation
duplicate genes
Proteins
proteins
gene
quantitative genetics
amino acid substitution
assays

Keywords

  • Arabidopsis
  • Brassicaceae
  • CTC1
  • positive selection
  • POT1
  • telomere

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology
  • Ecology, Evolution, Behavior and Systematics

Cite this

Evolution of the telomere-associated protein POT1a in arabidopsis thaliana is characterized by positive selection to reinforce protein-protein interaction. / Beilstein, Mark A; Renfrew, Kyle B.; Song, Xiangyu; Shakirov, Eugene V.; Zanis, Michael J.; Shippen, Dorothy E.

In: Molecular Biology and Evolution, Vol. 32, No. 5, 01.05.2015, p. 1329-1341.

Research output: Contribution to journalArticle

Beilstein, Mark A ; Renfrew, Kyle B. ; Song, Xiangyu ; Shakirov, Eugene V. ; Zanis, Michael J. ; Shippen, Dorothy E. / Evolution of the telomere-associated protein POT1a in arabidopsis thaliana is characterized by positive selection to reinforce protein-protein interaction. In: Molecular Biology and Evolution. 2015 ; Vol. 32, No. 5. pp. 1329-1341.
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