Patterns of divergence of a large family of nodule cysteine-rich peptides in accessions of Medicago truncatula

Sumitha Nallu, Kevin A.T. Silverstein, Peng Zhou, Nevin D. Young, Kathryn A. Vandenbosch

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The nodule cysteine-rich (NCR) groups of defensin-like (DEFL) genes are one of the largest gene families expressed in the nodules of some legume plants. They have only been observed in the inverted repeat loss clade (IRLC) of legumes, which includes the model legume Medicago truncatula. NCRs are reported to play an important role in plant-microbe interactions. To understand their diversity we analyzed their expression and sequence polymorphisms among four accessions of M. truncatula. A significant expression and nucleotide variation was observed among the genes. We then used 26 accessions to estimate the selection pressures shaping evolution among the accessions by calculating the nucleotide diversity at non-synonymous and synonymous sites in the coding region. The mature peptides of the orthologous NCRs had signatures of both purifying and diversifying selection pressures, unlike the seed DEFLs, which predominantly exhibited purifying selection. The expression, sequence variation and apparent diversifying selection in NCRs within the Medicago species indicates rapid and recent evolution, and suggests that this family of genes is actively evolving to adapt to different environments and is acquiring new functions.

Original languageEnglish (US)
Pages (from-to)697-705
Number of pages9
JournalPlant Journal
Volume78
Issue number4
DOIs
StatePublished - May 2014

Keywords

  • Medicago truncatula accessions
  • NCRs
  • diversifying selection in NCRs
  • expression polymorphism in NCRs
  • selection pressures on NCRs

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