The fractionated orthology of Bs2 and Rx/Gpa2 supports shared synteny of disease resistance in the Solanaceae.
Comparative genomics provides a powerful tool for the identification of genes that encode traits shared between crop plants and model organisms. Pathogen resistance conferred by plant R genes of the nucleotide-binding-leucine-rich-repeat (NB-LRR) class is one such trait with great agricultural importance that occupies a critical position in understanding fundamental processes of pathogen detection and coevolution. The proposed rapid rearrangement of R genes in genome evolution would make comparative approaches tenuous. Here, we test the hypothesis that orthology is predictive of R-gene genomic location in the Solanaceae using the pepper R gene Bs2. Homologs of Bs2 were compared in terms of sequence and gene and protein architecture. Comparative mapping demonstrated that Bs2 shared macrosynteny with R genes that best fit criteria determined to be its orthologs. Analysis of the genomic sequence encompassing solanaceous R genes revealed the magnitude of transposon insertions and local duplications that resulted in the expansion of the Bs2 intron to 27 kb and the frequently detected duplications of the 5'-end of R genes. However, these duplications did not impact protein expression or function in transient assays. Taken together, our results support a conservation of synteny for NB-LRR genes and further show that their distribution in the genome has been consistent with global rearrangements.
Mazourek
Michael
M
Department of Plant Breeding and Genetics, Cornell University, Ithaca, New York 1485, USA.
Cirulli
Elizabeth T
ET
Collier
Sarah M
SM
Landry
Laurie G
LG
Kang
Byoung-Cheorl
BC
Quirin
Edmund A
EA
Bradeen
James M
JM
Moffett
Peter
P
Jahn
Molly M
MM
D002212:Capsicum / Q000235:genetics; D015321:Gene Rearrangement; D017343:Genes, Plant; D018745:Genome, Plant / Q000235:genetics*; D023281:Genomics / Q000379:methods; D007113:Immunity, Innate / Q000235:genetics*; D010935:Plant Diseases / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics*; D019657:Solanaceae / Q000235:genetics*; D011198:Solanum tuberosum / Q000235:genetics; D026801:Synteny / Q000235:genetics*
C402462:BS2 protein, Capsicum chacoense; D010940:Plant Proteins; C120017:Rx protein, Solanum tuberosum