Abstract
BackgroundThe 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.ResultsWe 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.ConclusionFaster 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.
Highlights
The late blight pathogen Phytophthora infestans can attack both potato foliage and tubers
The +RB transgenic line exhibits enhanced tuber late blight resistance In previous field-based evaluations, the +RB line examined in this study, SP2211, was ranked as the third most foliar late blight resistant of 57 transgenic lines tested and was rated as “Resistant” to foliar late blight [5]
Results from two sets of whole tuber experiments were in agreement (32 of 33 P. infestans inoculations of WT tubers resulted in disease, none of the 60 inoculation sites in +RB tubers developed late blight disease)
Summary
The late blight pathogen Phytophthora infestans can attack both potato foliage and tubers. 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. P. infestans is a notorious plant destroyer with the capacity to attack both potato foliage and tubers. Gene RB (Rpi-blb1) [3,4], a disease resistance gene cloned from a wild potato species, confers broadspectrum foliar resistance against all major late blight pathogen isolates. Halterman et al [6] reported that the four foliar late blight resistant +RB transgenic potato lines examined in their study lacked statistically significant tuber blight resistance. RB has the potential to function in the tuber and the RB-potato tuber-P. infestans interaction provides a tractable system to study how potato tubers defend against plant pathogens
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