Identification and Cloning of Differentially Expressed Genes Involved in the Interaction Between Potato and Phytophthora infestans using a Subtractive Hybridization and cDNA-AFLP Combinational Approach

Using a subtractive hybridization (SH)/cDNA-AFLP combinational approach,differentially expressed genes involved in the potato-Phytophthora infestans interaction were identified.These included genes potentially controlling pathogenesis or avr genes in P.infestans as well as those potentially involved in potato resistance or susceptibility to this pathogen.Forty-one differentially expressed transcriptderived fragments (TDFs),resulting from the interaction,were cloned and sequenced.Two TDFs,suggested as potential pathogenicity factors,have sequence similarity to N-succinyl diaminopimelate aminotransferase and a transcriptional regulator,TetR family gene,respectively.Two other TDFs,suggested as potential avr genes,have sequence similarity to an EST sequence from Avr4/Cf-4/Avr9/Cf9 and a P.infestans avirulence-associated gene,respectively.Genes’ expression and origin were confirmed using Southern blots,Northern blots and qRT-PCR.I.e.,potential resistance gene DL81 was induced at 12 hpi in the moderately resistant cultivar,whereas it was down-regulated as early as 6 hpi in the susceptible cultivar.On the other hand,DL21 was induced at 6 hpi (3.38-fold) in response to the highly aggressive isolate (US8) and strongly up-regulated thereafter (25.13-fold at 120 hpi.),whereas it was only slightly up-regulated in response to the weakly aggressive isolate US11 (3.82-fold at 96 hpi),suggesting its potential involvement as a susceptibility gene.