Lr34 multi-pathogen resistance ABC transporter: Molecular analysis of homoeologous and orthologous genes in hexaploid wheat and other grass species

Simon Krattinger, Evans S. Lagudah, Thomas Wicker, Joanna M. Risk, Anthony R. Ashton, Liselotte L. Selter, Takashi Matsumoto, Beat Keller*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

The Triticum aestivum (bread wheat) disease resistance gene Lr34 confers durable, race non-specific protection against three fungal pathogens, and has been a highly relevant gene for wheat breeding since the green revolution. Lr34, located on chromosome 7D, encodes an ATP-binding cassette (ABC) transporter. Both wheat cultivars with and without Lr34-based resistance encode a putatively functional protein that differ by only two amino acid polymorphisms. In this study, we focused on the identification and characterization of homoeologous and orthologous Lr34 genes in hexaploid wheat and other grasses. In hexaploid wheat we found an expressed and putatively functional Lr34 homoeolog located on chromosome 4A, designated Lr34-B. Another homoeologous Lr34 copy, located on chromosome 7A, was disrupted by the insertion of repetitive elements. Protein sequences of LR34-B and LR34 were 97% identical. Orthologous Lr34 genes were detected in the genomes of Oryza sativa (rice) and Sorghum bicolor (sorghum). Zea mays (maize), Brachypodium distachyon and Hordeum vulgare (barley) lacked Lr34 orthologs, indicating independent deletion of this particular ABC transporter. Lr34 was part of a gene-rich island on the wheat D genome. We found gene colinearity on the homoeologous A and B genomes of hexaploid wheat, but little microcolinearity in other grasses. The homoeologous LR34-B protein and the orthologs from rice and sorghum have the susceptible haplotype for the two critical polymorphisms distinguishing the LR34 proteins from susceptible and resistant wheat cultivars. We conclude that the particular Lr34-haplotype found in resistant wheat cultivars is unique. It probably resulted from functional gene diversification that occurred after the polyploidization event that was at the origin of cultivated bread wheat.

Original languageEnglish (US)
Pages (from-to)392-403
Number of pages12
JournalPlant Journal
Volume65
Issue number3
DOIs
StatePublished - Feb 1 2011

Keywords

  • Lr34
  • comparative analysis
  • disease resistance
  • gene diversification
  • orthologous genes
  • polyploid wheat

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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