Biology Reference
In-Depth Information
Coiled-coil-NBS-LRR and Toll-Interleukin
receptor NBS-LRR. Resistance gene analogs
(RGAs) were identified in several linkage groups
of common bean using degenerated primers
that targeted the conserved domains of R genes
(Lopez et al. 2003). Some RGAs were located
in the relative position of anthracnose resistance
genes. A molecular characterization in detail
was carried out in several regions including
anthracnose resistance loci. Genomic analyses
revealed the presence of R genes organized in
clusters including several nucleotide sequences
that code for R proteins. In plants, genes
encoding NBS-LRR are often located at cluster
of tightly linked loci (Dangl and Jones 2001;
McDowell and Woffenden 2003). This molec-
ular organization of genes in complex clusters,
encoding resistances to diverse pathogens or
to different races of the same pathogen, is
supported by genetic evidence from different
species (Kanazin et al. 1996; Michelmore and
Myers 1998; Sharma et al. 2004).
LinkageGroupPv04
A complex cluster of resistance genes including
the resistant genes to numerous races or isolates
are located at the end of Pv04, cluster Co-3, or
B4 resistance (R) gene cluster. Four expressed
resistance gene candidates that map at the Co-
3 cluster and co-localize with R-specificities
or R-QTLs effective against
C. lindemuthi-
anum
were analyzed in the bean genotypes
BAT93 and JaloEEP558. These candidate genes
encode NBS-LRR proteins (Ferrier-Cana et al.
2003).
Six bacterial artificial chromosome clones
(BAC), derived from genotype BAT93 and
located in same relative position as the Co-3
cluster, were sequenced. The analyzed region
approximately corresponds to 29 cM in the
genetic linkage map. A total of 97 genes, 26 of
which correspond to coiled-coil-NBC-LRR pro-
teins, were annotated. These 26 NBS-LRR genes
were identified in the approximately 650 kb
sequence and they are organized in four subclus-
ters. Fluorescent in situ hybridization of mei-
otic pachytene chromosomes revealed that these
sequences are located in the subtelomeric region
of the short arm of chromosome 4 (Pv04). Phy-
logenetic analysis showed a closely relationship
of this Co-3 (Pv04) cluster and the Co-2 clus-
ter (Pv11) suggesting an ectopoic recombination
event in the legume (David et al. 2009, 2010;
Geffroy et al. 2009). DNA sequences from clus-
ter Co-3 and derived from the genotypes BAT93
and JaloEEP558 were compared and different
numbers of genes encoding for NBS-LRR pro-
teins were found. In addition, the sequencing
and annotation of one BAC clone located at
the Co-3 cluster revealed three genes encoding
for formate dehydrogenase (FDH), an enzyme
involved in the oxidation of formate into CO
2
.
FDH protein accumulation and increased activ-
ity has been correlated with abiotic stress in
different plant species. FDH genes are differ-
entially up-regulated after infection with iso-
late M126 of
C. lindemuthianum
(David et al.
2010).
LinkageGroupPv02
A large cluster of NBS-LRR sequences asso-
ciated within the
I
locus that is involved in
the response to several related potyviruses was
described in the bean genotype Sprite (Valle-
jos et al. 2006). The
I
locus was located at
the end of Pv02 in several genetic maps. The
Co-u resistance gene conferring resistance to
anthracnose isolates E4 and E42b was located
in the relative position of the
I
gene (Geffroy
et al. 2008). Polygalacturonase-inhibiting pro-
teins (PGIPs) family was mapped in the Pv02
linkage group, although its relative position was
not specified (Freyre et al. 1998). PGIPs are
extracellular plant inhibitors of fungal endopoly-
galacturonases (PGs) that belong to the fam-
ily of LRR proteins. PGIP family in the
bean genotype BAT93 comprises four clus-
tered genes that span a 50-kb region (D'Ovidio
et al. 2004). The relation of this cluster of
genes with resistance to anthracnose should be
verified.
Search WWH ::
Custom Search