RNA-seq Analysis Of Potato Leaves During The Early Stage Of Phytophthora Infestans Infection

Potato is the fourth most important food crop in the world after corn,rice and wheat.It not only plays an important role in the daily consumption of residents,but also adjusts the agricultural structure and continuously increases farmers' income.The sustainable production of potato is seriously threatened by late blight pathogen,Phytophthora infestans,an extraordinarily virulent and adaptable pathogen.P.infestans belongs to oomycetes,a group that is phylogenetically distant from true fungi.These make significant differences in physiological and biochemical characteristics,and lead to ineffectiveness of some fungicides against P.infestans.Therefore,improved understanding of the interaction between potato and P.infestans not only requires for revealing the underlying mechanisms of the interaction,but also plays a very important role in development of efficient late blight control measures.Based on the previous P.infestans population analysis in our lab,five genetically diverse strains were selected and 12 hours of early infection samples were prepared for RNA-seq to explore the response of potato upon P.infestans infection.The results are summarized as follows:1.In response to P.infestans infection,a large number of defense related genes were up-regulated in potato leaves,including those related to secondary metabolic pathways,cell-to-cell signal transduction,negative-regulatory enzyme activities,and genes related to salicylic acid,jasmonic acid,and ethylene signaling pathways.Most of the PAMP-induced genes were up-regulated.Genome-wide identification of the potato transcription factors reveals that the vast majority of WRKY transcription factors were up-regulated.Photosynthetic and protein translation-related genes were down-regulated.2.Analysis of genes encoding potato receptor-like kinases showed that the RLK-Pelle_DLSV and RLK-Pelle_LRK10L-2 subfamily genes undergo a large number of duplications and nearly half of them were upregulated.These results provide important candidates for subsequent identification of PAMP recognition receptors.3.Analysis of the potato NBS-LRR protein family genes showed a unique distribution of potato disease resistance genes,and the expansion of CNL subfamily is faster than TNL subfamily.Although fewer genes were differentially expressed,it was also consistent with the susceptibility characteristics of MaR3.Up to 223 novel NBS-LRR gene loci were identified and suggested the possibility of exploring NBS-LRR resistance genes through RNA-seq.4.A large number of protease inhibitor genes were identified highly up-regulated,and virus-induced gene silencing approach was employed to figure out their roles in resistance by silencing homologous genes in Nicotiana benthamiana.The result showed that Nb-PI2 significantly increased plant susceptibility to Phytophthora infection among three protease inhibitor genes examined,it indicated that the protease inhibitor genes are involved in defense regulation of the host plant.