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Multiple rRNA Variants in a Single Spore of the Microsporidian Nosema bombi

Authors

  • ELAINE M. O'MAHONY,

    1. School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom, and
    2. Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JT, United Kingdom, and
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    • *These authors contributed equally to this paper.

  • WEE TEK TAY,

    1. School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom, and
    2. ARC Special Research Centre for Environmental Stress and Adaptation Research (CESAR), Department of Genetics, Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Melbourne, Vic. 3010, Australia
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    • *These authors contributed equally to this paper.

  • ROBERT J. PAXTON

    1. School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, United Kingdom, and
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Corresponding Author: E. O'Mahony, Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JT, United Kingdom—Telephone number: +44 (0) 131 6508661; Fax number: +44 (0) 131 6506564; e-mail: eomahony@staffmail.ed.ac.uk

Abstract

ABSTRACT. To understand the source of the multiple DNA sequence variants of Nosema bombi ribosomal RNA (rRNA) found in a single bumble bee host, we PCR amplified, cloned, and sequenced the partial rRNA gene from 125 clones, which were derived from four out of 46 spores individually isolated from a single host by laser microdissection. At least two rRNA variants, characterized by either (GTTT)2 or (GTTT)3 repeat units within the internal transcribed spacer (ITS) region, were found per spore in approximately equal proportions, variants which were also found in approximately equal proportions in 55 clones of the two DNA extracts of multiple spores from the same host. Firstly, we demonstrate for the first time that DNA sequences can be obtained from single-binucleate microsporidia. Secondly, it appears that concerted evolution has not homogenized the sequences of all rRNA copies within a single N. bombi spore or even within a single nucleus. We thereby demonstrate unequivocally that two or more rRNA sequence variants exist per N. bombi spore, and urge caution in the use of multicopy rRNA genes for population genetic and phylogenetic analysis of this and other Microsporidia unless homologous copies can be reliably typed.

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