Transgenic tomato lines expressing human lactoferrin show increased resistance to bacterial and fungal pathogens

Agrobacterium-mediated transformation of tomato (Lycopersicon esculentum Mill.) plants was carried out to transfer the human lactoferrin gene (hLf) under control of the constitutive Cauliflower Mosaic Virus (CaMV) 35 S promoter to increase their resistance to phytopathogens. Since binary plasmid construct contained also neomycin phosphotransferase gene (nptII) conferring resistance to kanamycin, the selection of transgenic lines was carried out on nutrient medium supplemented with 100 mg/L kanamycin (as selective agent). PCR and Western blot analyses of transformed lines with primers specific to hLf gene and a monoclonal antibody against lactoferrin were performed to confirm the transgenic nature of selected tomato plants and hLf gene expression. The resistance of transgenic tomato lines expressing hLf to bacterial pathogens Clavibacter michiganensis subsp. michiganensis (causing bacterial wilt and canker of tomato), and Ralstonia solanacearum (causing bacterial wilt), and fungal pathogen Phytophthora infestans (causing late blight) was demonstrated. Although the partial resistance to bacterial wilt in transgenic tomatoes expressing modified lactoferrin has already been shown (Lee et al., 2002), here we report for the first time that the transfer and the expression of human lactoferrin gene in transgenic tomato plants leads to their enhanced resistance not only to R. solanacearum but also to another bacterial pathogen C. michiganensis and to fungal pathogen P. infestans. The present study demonstrates that the genetic transformation of plants with the human lactoferrin gene (hLf) is a promising technology to increase the resistance of plant species to certain phytopathogens.