Insights into organ-specific pathogen defense responses in plants: RNA-seq analysis of potato tuber-Phytophthora infestans interactions

The late blight pathogen Phytophthora infestans can attack both potato foliage and tubers. Although interaction transcriptome dynamics between potato foliage and various pathogens have been reported, no transcriptome study has focused specifically upon how potato tubers respond to pathogen infection. When inoculated with P. infestans, tubers of nontransformed 'Russet Burbank' (WT) potato develop late blight disease while those of transgenic 'Russet Burbank' line SP2211 (+RB), which expresses the potato late blight resistance gene RB (Rpi-blb1), do not. We compared transcriptome responses to P. infestans inoculation in tubers of these two lines.We demonstrated the practicality of RNA-seq to study tetraploid potato and present the first RNA-seq study of potato tuber diseases. A total of 483 million paired end Illumina RNA-seq reads were generated, representing the transcription of around 30,000 potato genes. Differentially expressed genes, gene groups and ontology bins that exhibited differences between the WT and +RB lines were identified. P. infestans transcripts, including those of known effectors, were also identified.Faster and stronger activation of defense related genes, gene groups and ontology bins correlate with successful tuber resistance against P. infestans. Our results suggest that the hypersensitive response is likely a general form of resistance against the hemibiotrophic P. infestans-even in potato tubers, organs that develop below ground.