Expression of a depolymerase gene in transgenic pears increased only slightly their fire blight resistance
2002
Malnoy, M. | Chevreau, E. | Brisset, M.N.
Fire blight, caused by Erwinia amylovora, is a major disease of pear (Pyrus communis L.). Different strategies to enhance fire blight resistance of pear through genetic engineering are currently studied in our group. Among them, transformation of pear with a depolymerase gene from a bacteriophage has been investigated. This gene encodes an enzyme that degrades the capsular exopolysaccharide (EPS) of E. amylovora. Mutant strains without bacterial EPS are known to fail to colonize host plants. Pear cv. ‘Passe Crassane’ was transformed with Agrobacterium tumefaciens EHA105pBinAR-dpo carrying the depolymerase gene under the control of the CaMV35S promoter. Sixteen transgenic diploid clones were obtained and analysed by western blot and RT-PCR. In vitro tests for fire blight resistance were performed by inoculation with a virulent strain of E. amylovora. Two transgenic clones showed a slight reduction of fire blight symptoms (about 15 %) in comparison to non-transformed plants. This partial resistance was correlated with a stronger expression of the transgene at transcriptional and traductional levels. Very low depolymerase activity was detected in most transgenic clones (0.006% of total soluble proteins). Greenhouse evaluation of fire blight resistance of the depolymerase clones is under investigation on acclimatized plants.
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