Between-species analysis of short-repeat modules in cell wall and sex-related hydroxyproline-rich glycoproteins of Chlamydomonas.

Jae-Hyeok Lee,Linda Small,Ursula Goodenough,Sabine Waffenschmidt

doi:10.1104/pp.107.100891

Jae-Hyeok Lee, Linda Small + Show 2 more

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https://doi.org/10.1104/pp.107.100891

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Journal: Plant Physiology	Publication Date: Jun 15, 2007
Citations: 42	License type: CC BY 4.0

Affiliation: University of Washington

Abstract

Protein diversification is commonly driven by single amino acid changes at random positions followed by selection, but, in some cases, the structure of the gene itself favors the occurrence of particular kinds of mutations. Genes encoding hydroxyproline-rich glycoproteins (HRGPs) in green organisms, key protein constituents of the cell wall, carry short-repeat modules that are posited to specify proline hydroxylation and/or glycosylation events. We show here, in a comparison of two closely related Chlamydomonas species-Chlamydomonas reinhardtii (CC-621) and Chlamydomonas incerta (CC-1870/3871)-that these modules are prone to misalignment and hence to both insertion/deletion and endoduplication events, and that the dynamics of the rearrangements are constrained by purifying selection on the repeat patterns themselves, considered either as helical or as longitudinal face modules. We suggest that such dynamics may contribute to evolutionary diversification in cell wall architecture and physiology. Two of the HRGP genes analyzed (SAG1 and SAD1) encode the mating-type plus and minus sexual agglutinins, displayed only by gametes, and we document that these have undergone far more extensive divergence than two HRGP genes (GP1 and VSP3) that encode cell wall components-an example of the rapid evolution that characterizes sex-related proteins in numerous lineages. Strikingly, the central regions of the agglutinins of both mating types have diverged completely, by selective endoduplication of repeated motifs, since the two species last shared a common ancestor, suggesting that these events may have participated in the speciation process.

Highlights

Protein diversification is commonly driven by single amino acid changes at random positions followed by selection, but, in some cases, the structure of the gene itself favors the occurrence of particular kinds of mutations
Plant Physiology, August 2007, Vol 144, pp. 1813–1826, www.plantphysiol.org Ó 2007 American Society of Plant Biologists Downloaded from on October 5, 2020 - Published by www.plantphysiol.org approximately three amino acids per helical gyre, this generates three longitudinal faces along the long axis of a shaft, each face separated from the by approximately 120° (Ferris et al, 2005)
In the diagrams (Fig. 1, A–D), the primary amino acid sequence of each shaft is arranged in three separate rows such that residues in every third position appear in a single row

Summary

Introduction

Protein diversification is commonly driven by single amino acid changes at random positions followed by selection, but, in some cases, the structure of the gene itself favors the occurrence of particular kinds of mutations. In a comparison of two closely related Chlamydomonas species—Chlamydomonas reinhardtii (CC-621) and Chlamydomonas incerta (CC-1870/3871)—that these modules are prone to misalignment and to both insertion/deletion and endoduplication events, and that the dynamics of the rearrangements are constrained by purifying selection on the repeat patterns themselves, considered either as helical or as longitudinal face modules. We suggest that such dynamics may contribute to evolutionary diversification in cell wall architecture and physiology.

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