EXPRESSION OF PHI-EA1H PHAGE DEPOLYMERASE GENE WITH CONSTITUTIVE AND INDUCIBLE PROMOTERS, TRANSLATION ENHANCER AND SIGNAL SEQUENCE IN TRANSGENIC APPLE PLANTS INCREASES RESISTANCE TO FIRE BLIGHT

Fire blight, caused by the bacterium Erwinia amylovora, is a major disease of apple (Malus × domestica). Among different strategies to enhance fire blight resistance of apple through genetic engineering, transformation of apple with the dpo gene from the bacteriophage phi-Ea1h was investigated.
This gene encodes a depolymerase that degrades the capsular exopolysaccharide of E. amylovora. Previous work in other labs had shown no, or a slight, increase in fire blight resistance by expression of a dpo transgene in apple.
In the present research, the apple rootstock ‘M.26’, which is highly susceptible to fire blight, was transformed with a binary vector (p35SAMVSPdpo or pGST1Spdpo) carrying the dpo gene under the control of the constitutive CaMV35S or pathogen-inducible gst1 promoter, respectively.
The dpo gene was also fused to the AMV translation enhancer and to a signal sequence.
Nine and eleven dpo transgenic diploid apple clones with the CaMV35S or gst1 promoter, respectively, were obtained and analyzed by RT-PCR. Greenhouse tests for fire blight resistance were performed by inoculation with the virulent Ea 273 strain of E. amylovora at 5 x 107 cfu/ml.
The preliminary data showed an increase in resistance in some transgenic lines that expressed p35SAMVSPdpo or pGST1SPdpo.
The level of resistance was higher in plants expressing p35SAMVSPdpo compared with the level in plants expressing pGST1SPdpo.
Determination of DPO activity and the quantity of DPO in the transgenic lines is underway.

International Symposium on Biotechnology of Temperate Fruit Crops and Tropical Species

E.E. Borejsza-Wysocka, M. Malnoy, W.S. Kim, K. Geider, S.V. Beer, H.S. Aldwinckle

fire blight, apple, transgenics, depolymerase, resistance

https://doi.org/10.17660/ActaHortic.2007.738.28