Overexpression of the Arabidopsis thaumatin-like protein 1 in transgenic potato plants enhances resistance against early and late blights

The Arabidopsis thaumatin-like protein 1 (ATLP1), which belongs to the PR5 family of pathogenesis-related proteins, is induced by pathogen attacks and by systemic acquired resistance (SAR)-inducing compounds. To test whether the overexpression of ATLP1 will enhance fungal resistance in transgenic plants, the cDNA of this gene under the control of a constitutive promoter was transferred into Solanum tuberosum Cv. Desiree. The expression of the introduced gene was confirmed by Northern and Western blot analyses. Western blot analysis performed with intercellular fluid (ICF) showed that ATLP1 is secreted to apoplast. Several independent transgenic lines with high-level expression of the ATLP1 were assayed for resistance against early blight (Alternaria solani) and late blight (Phytophthora infestans). The rate of Alternaria lesions development was significantly reduced in the ATLP1 transgenic lines as compared to a control line. Percent reductions in area under the disease progress curve (AUDPC) values for the ATLP1 transgenic lines as compared to control line ranged between 52 and 82%. In response to P. infestans, infection efficiency (IE), lesion size (LS) and sporulation capacity (SC) were significantly reduced in ATLP1 transgenic lines as compared to a control line. On the average, IE, LS and SC were reduced by 18, 22 and 20%, respectively, for all transgenic lines with a maximum reduction of 25% in IE, 25% in LS and 32% in SC. Resistance assays against P. infestans using whole plants showed 40-70% reduction in symptoms as compared to control. These results suggest that constitutive expression of a heterologous ATLP in potato confers enhanced resistance against early and late blights.