A homolog of the RPS2 disease resistance gene is constitutively expressed in Brassica oleracea

Abstract

In this study, we identified disease resistance gene homologs in Brassica oleracea and assessed their expression in lines resistant and susceptible to Xanthomonas campestris pv. campestris (Xcc). Two DNA fragments of approximately 2.5 kb (BI-16/RPS2 and Lc201/RPS2) were amplified by PCR from two Brassica lines using primers based on an RPS2 homologous sequence previously described in the Brassica oleracea ecotype B117. The sequences of these fragments shared high similarity (95-98%) with RPS2 homologs from various Brassica species. The digestion of these fragments with restriction enzymes revealed polymorphisms at the Xba I restriction sites. The length polymorphisms were used as a co-dominant marker in an F 2 population developed to segregate for resistance to Xcc, the causal agent of black rot. Linkage analysis showed no significant association between the marker and quantitative trait loci for black rot. RT-PCR with specific primers yielded an expected 453 bp fragment that corresponded to the RPS2 homologs in both resistant and susceptible lines inoculated with the pathogen, as well as in non-inoculated control plants. These results suggest that these homologs are constitutively expressed in B. oleracea.

Genome-wide comparative analysis of NBS-encoding genes between Brassica species and Arabidopsis thaliana

“…Earlier Wroblewski et al [ 50 ] identified RPS2 homologs with high nucleotide similarity in Brassica species, like B. montana AF180358 (98% identity), B. oleracea AF180357 (98% identity) and B. rapa AF180359 (95% identity). Later Malvas et al [ 51 ] also described the involvement of B. oleracea RPS2 homolog in disease resistance which is constitutively expressed. In our study, two CNL type NBS genes, one in B. rapa (Bra013947-previous GenBank ID AF180359) and one in B. oleracea (Bol039594- previous GenBank ID AF180357) were found to be conserved parallel to the RPS2 gene with 94.59% nucleotide similarity.…”

Genetic diversity and evolution ofBrassicagenetic resources: from morphology to novel genomic technologies – a review

“…Malvas et al . (2003) identified two DNA fragments of RPS2 gene homologues in two Brassica lines resistant and susceptible to Xcc. The digestion of these fragments with restriction enzymes showed polymorphisms at the XbaI restriction sites.…”

“…RFLP markers have been used in studying genetic variability and relationships in plant species, for example, Lathyrus (Chtourou-Ghorbel et al, 2001) and Pleurotus eryngii (Urbanelli et al, 2007). RFLP markers have also been used in assessing genetic variation and developing detailed genetic maps of Brassica (Diers and Osborn, 1994;Diers et al, 1996;Pradhan et al, 2003) and lettuce (Landry et al, 1987;Kesseli et al, 1994), assessing polymorphisms in Brassica lines resistant and susceptible to Xcc (Malvas et al, 2003;El-Esawi, 2012), and identification of origin of cultivated lettuce (Kesseli et al, 1991). Malvas et al (2003) identified two DNA fragments of RPS2 gene homologues in two Brassica lines resistant and susceptible to Xcc.…”