Natural variation, functional divergence, and local adaptation of nucleotide binding site sequences in Rhododendron (Ericaceae)

Pei Chun Liao, Jeng Der Chung, Chia Ling Chen, Chiun Jr Hwang, Ya Hsiu Sung, Yung-Ta Chang, Shih Ying Hwang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

To further understand natural variation and local adaptation in the evolution of plant defense, we analyzed polymorphism data of nucleotide-binding site (NBS) sequences of Rhododendron at both the species and population levels. Multiple duplication events were found in NBS sequence evolution in Rhododendron genomes, which resulted in six clades: A-F. Our results of several NBS clade pair comparisons showed significant evolutionary rate changes based on differences in substitution rates between NBS-encoding protein clades (type I functional divergence). Pairwise comparisons of NBS clades further revealed that many amino acids displayed radical biochemical property changes causing a shift in amino acid preferences between NBS-encoding protein clades (type II functional divergence). Such divergent evolution of NBSs is likely a consequence of positive selection related to differentiation of recognition signals in response to different pathogens. Primers specific to clades B and C, which differed in the number of radical amino acid changes causing type II functional divergence and levels of nucleotide diversities, were further used to amplify population clades B and C NBS sequences of Rhododendron formosanum populations. Higher levels of net nucleotide divergences (measured by D a) between R. formosanum populations were found based on NBS sequences of population clade B compared to population clade C, suggesting local adaptation of population clade B NBS sequences. Local adaptation can be further inferred for R. formosanum population clade B NBS sequences because of significant Φ ST based on variation in nonsynonymous substitutions. Furthermore, local adaptation was also suggested by no significant correlation of population pairwise F ST between population clades B and C in R. formosanum.

Original languageEnglish
Pages (from-to)879-893
Number of pages15
JournalTree Genetics and Genomes
Volume8
Issue number4
DOIs
Publication statusPublished - 2012 Aug

Keywords

  • Functional divergence
  • Local adaptation
  • Nucleotide-binding-site domain
  • Positive selection
  • Rhododendron

ASJC Scopus subject areas

  • Forestry
  • Molecular Biology
  • Genetics
  • Horticulture

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