An Erwinia Amylovora inducible promoter for intragenic improvement of Apple Fire blight resistance
Résumé
Intragenesis is an important alternative to transgenesis to produce modied plants containing native DNA only but allowing a reorganization of bothregulatory and coding sequences, as well as the introduction of mutations. A key point to develop such a strategy is the availability of regulatorysequences controlling the expression of the gene of interest. With the aim of nding apple gene promoters either inducible by the re blight pathogenErwinia amylovora (Ea) or moderately constitutive, we focused on polyphenoloxidase genes (PPO). These genes encode oxidative enzymes involved inmany physiological processes and have been previously shown to be up-regulated during the Ea infection process. We found ten PPO sequences in theapple genome and characterized the promoter of MdPPO16 (pPPO16) for its potential as Ea-inducible regulatory sequence. Expression levels ofreporter genes fused to this promoter and transiently or stably expressed in apple were quantied after various treatments. pPPO16 allowed a fastand strong expression of transgenes in apple following Ea infection in a Type 3 Secretion System dependent manner. Altogether our results indicatethat pPPO16, the rst Ea-inducible promoter cloned from apple, can be a useful component of intragenic strategies to create re blight resistant applegenotypes.