Two poplar methyl salicylate esterases display comparable biochemical properties but divergent expression patterns

Two methyl salicylate (MeSA) esterase (SABP2) genes, PtSABP2-1 and PtSABP2-2, were identified and cloned from poplar. The proteins encoded by PtSABP2-1 and PtSABP2-2 are 98% identical. Recombinant PtSABP2-1 and PtSABP2-2 displayed specific methyl esterase activity using MeSA as substrate to produce salicylic acid (SA). In addition to exhibiting comparable biochemical properties, PtSABP2-1 and PtSABP2-2 have conserved structural features. In contrast, PtSABP2-1 and PtSABP2-2 showed divergent expression patterns. The plausible evolutionary mechanisms leading to these two highly homologous MeSA esterase genes involved in divergent biological processes in poplar are discussed.