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TitleOrganization and evolution of resistance gene analogs in peanut
AuthorsBayram Yuksel, James C. Estill, Stefan R. Schulze, Andrew H. Paterson
PublicationMol Gen Genomics 274: 248-263
AbstractThe scarcity of genetic polymorphism in Arachis
hypogaea (peanut), as in other monophyletic polyploid
species, makes it especially vulnerable to
nematode, bacterial, fungal, and viral pathogens. Although
no disease resistance genes have been cloned
from peanut itself, the conserved motifs in cloned
resistance genes from other plant species provide a
means to isolate and analyze similar genes from peanut.
To survey the number, diversity, evolutionary history,
and genomic organization of resistance gene-like sequences
in peanut, we isolated 234 resistance gene analogs
(RGAs) by using primers designed from conserved
regions of different classes of resistance genes including
NBS-LRR, and LRR-TM classes. Phylogenetic and sequence
analyses were performed to explore evolutionary
relationships both among peanut RGAs and with orthologous
genes from other plant taxa. Fifty-six overgos
designed from the RGA sequences on the basis of their
phyletic association were applied to a peanut BAC library;
736 hybridizing BAC clones were fingerprinted
and contigs were formed in order to gain insights into
the genomic organization of these genes. All the fingerprinting
gels were blotted and screened with the
respective overgos in order to verify the authenticity of
the hits from initial screens, and to explore the physical
organization of these genes in terms of both copy
number and distribution in the genome. As a result, we
identified 250 putative resistance gene loci. A correlation
was found between the phyletic positions of the sequences
and their physical locations. The BACs isolated
here will serve as a valuable resource for future applications,
such as map-based cloning, and will help improve
our understanding of the evolution and
organization of these genes in the peanut genome.

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.: 2009 :: Barry Marler :: Plant Genome Mapping Laboratory :: University of Georgia