Molecular Genetics and Genomics

, Volume 280, Issue 2, pp 111–125

Genetic diversity and genomic distribution of homologs encoding NBS-LRR disease resistance proteins in sunflower

  • Osman Radwan
  • Sonali Gandhi
  • Adam Heesacker
  • Brett Whitaker
  • Chris Taylor
  • Alex Plocik
  • Richard Kesseli
  • Alexander Kozik
  • Richard W. Michelmore
  • Steven J. Knapp
Original Paper

Abstract

Three-fourths of the recognition-dependent disease resistance genes (R-genes) identified in plants encode nucleotide binding site (NBS) leucine-rich repeat (LRR) proteins. NBS-LRR homologs have only been isolated on a limited scale from sunflower (Helianthus annuus L.), and most of the previously identified homologs are members of two large NBS-LRR clusters harboring downy mildew R-genes. We mined the sunflower EST database and used comparative genomics approaches to develop a deeper understanding of the diversity and distribution of NBS-LRR homologs in the sunflower genome. Collectively, 630 NBS-LRR homologs were identified, 88 by mining a database of 284,241 sunflower ESTs and 542 by sequencing 1,248 genomic DNA amplicons isolated from common and wild sunflower species. DNA markers were developed from 196 unique NBS-LRR sequences and facilitated genetic mapping of 167 NBS-LRR loci. The latter were distributed throughout the sunflower genome in 44 clusters or singletons. Wild species ESTs were a particularly rich source of novel NBS-LRR homologs, many of which were tightly linked to previously mapped downy mildew, rust, and broomrape R-genes. The DNA sequence and mapping resources described here should facilitate the discovery and isolation of recognition-dependent R-genes guarding sunflower from a broad spectrum of economically important diseases.

Keywords

Helianthus Lactuca Compositae Resistance genes 

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Osman Radwan
    • 1
    • 2
  • Sonali Gandhi
    • 3
  • Adam Heesacker
    • 1
  • Brett Whitaker
    • 1
  • Chris Taylor
    • 1
  • Alex Plocik
    • 4
  • Richard Kesseli
    • 4
  • Alexander Kozik
    • 5
  • Richard W. Michelmore
    • 5
  • Steven J. Knapp
    • 1
  1. 1.Center for Applied Genetic TechnologiesThe University of GeorgiaAthensUSA
  2. 2.Plant Production Department, Efficient Productivity InstituteUniversity of ZagazigSharkiaEgypt
  3. 3.Department of Crop and Soil ScienceOregon State UniversityCorvallisUSA
  4. 4.Department of BiologyUniversity of MassachusettsBostonUSA
  5. 5.Department of Plant Sciences and the Genome CenterUniversity of CaliforniaDavisUSA

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