|P.C.S. Angelo, L.F.P. Pereira, G.H. Sera, E.T. Caixeta
|plant-pathogen recognition, gene-to-gene interaction, leucine rich repeats
Genes in coffee SH3 loci are involved in the interaction with the fungus Hemileia vastatrix. Previously we found, by comparison to data published for C. arabica ‘IAPAR 59’, that SH3 loci are multi-alellic and complex in the publicly available genomes of Coffea arabica ‘Caturra’, C. eugenioides and C. canephora. The above cited SH3 loci display different numbers of copies of a CC-NBS-LRR gene, in distinctive organizations.
In its turn, C. liberica is considered to display an SH3 configuration ideal to provide durable resistance to leaf rust, which is highly desirable and pursued.
The CC-NBS-LRR genes in the coffee SH3 loci display highly conserved as well as hypervariable regions.
Sets of primers designated to amplify the hypervariable LRR-carboxy terminals were used to clone and sequence SH3 variants in C. liberica and ‘IAPAR 59’. Neighbor-joining was used to graphically represent pairwise divergence indexes between the deduced peptide sequences. ‘IAPAR 59’. was re-accessed as a testimony for the approach’s effectiveness because it was possible to verify that all the variants previously reported elsewhere for SH3 genes in ‘IAPAR 59’ BAC clones were also cloned using our primer sets.
Indeed, it was considered that all the variants present in the accessed C. liberica plant had also been cloned.
This was further checked by contrasting the restriction fragment maps coming from genomic DNA × cloned amplicons in the two genotypes: patterns for both DNA sources of a same genotype were equal, and diverged from those in the other genotype.
Regarding sequences, at least three out of six carboxy-terminal variants found in C. liberica seem to be exclusive when contrasted to the other four genotypes accessed.
Differences found in the restriction maps and sequences are very likely related to susceptibility or resistance reactions verified during coffee plants-H. vastatrix physiological race interactions.
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