The major resistance gene cluster in lettuce is highly duplicated and spans several megabases

Meyers, B C and Chin, D B and Shen, K A and Sivaramakrishnan, S and Lavelle, D O and Zhang, Z and Michelmore, R W (1998) The major resistance gene cluster in lettuce is highly duplicated and spans several megabases. The Plant Cell, 10 (11). pp. 1817-1832. ISSN 1040-4651

PDF Restricted to ICRISAT users only Download (378kB) | Request a copy

Abstract

At least 10 Dm genes conferring resistance to the oomycete downy mildew fungus Bremia lactucae map to the major resistance cluster in lettuce. We investigated the structure of this cluster in the lettuce cultivar Diana, which contains Dm3. A deletion breakpoint map of the chromosomal region flanking Dm3 was saturated with a variety of molecular markers. Several of these markers are components of a family of resistance gene candidates (RGC2) that encode a nucleotide binding site and a leucine-rich repeat region. These motifs are characteristic of plant disease resistance genes. Bacterial artificial chromosome clones were identified by using duplicated restriction fragment length polymorphism markers from the region, including the nucleotide binding site-encoding region of RGC2. Twenty-two distinct members of the RGC2 family were characterized from the bacterial artificial chromosomes; at least two additional family members exist. The RGC2 family is highly divergent; the nucleotide identity was as low as 53% between the most distantly related copies. These RGC2 genes span at least 3.5 Mb. Eighteen members were mapped on the deletion breakpoint map. A comparison between the phylogenetic and physical relationships of these sequences demonstrated that closely related copies are physically separated from one another and indicated that complex rearrangements have shaped this region. Analysis of low-copy genomic sequences detected no genes, including RGC2, in the Dm3 region, other than sequences related to retrotransposons and transposable elements. The related but divergent family of RGC2 genes may act as a resource for the generation of new resistance phenotypes through infrequent recombination or unequal crossing over

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Subjects:	Others
Depositing User:	Ms K Syamalamba
Date Deposited:	16 May 2013 11:08
Last Modified:	16 May 2013 11:08
URI:	http://oar.icrisat.org/id/eprint/6806
Official URL:	http://dx.doi.org/10.1105/tpc.10.11.1817
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	UNSPECIFIED
Links:	Google Scholar

View Statistics

Actions (login required)

View Item