Artifical MicroRNA Mediated Gene Silencing of Phytophthora infestans Single Effector Avr3a Gene Imparts Moderate Type of Late Blight Resistance in Potato

摘要

RNAi based "host plant mediated pathogen gene silencing" has emerged as a novel strategy for the efficient control of pathogens infecting various important food crops. Artifical microRNAs (amiRNAs) represent a robust and recently developed miRNA basedstrategy for the effective posttranscriptional gene silencing in plants. Phytophthora infestans RXLR effector Avr3a suppresses hypersensitive cell death in host cells and responsible for virulence. In the present investigation, the effect of artificialmicroRNAs are studied on the target transcript, Avr3a gene of P. infestans. Five Avr3a amiRNA gene constructs developed targeting five different regions of Avr3a gene of P. infestans and were transformed into two popular Indian potato cultivars i.e., Kufri Khyati and Kufri Pukharaj. Screening analysis study revealed that most of the transgenic lines were susceptible (15) and few lines (4) were found to be moderately or partially resistance. Target effector gene expression level and the pathogen load were determined to identify whether the resistant observed was RNA mediated. Real time PCR analysis showed that there is reduction in pathogen load as well as in transcript level of Avr3a in resistant lines as compared to the non-transgenic control. This revealed that, the invading P. infestans withdraws the dsRNA/amiRNAs from the host cell leading to the silencing of the Avr3a gene expression causing pathogen death and/or loss of virulence. The amiRNA technology developed in this study appears to be potential and promising for durable and long lasting resistance in potato to combat the notorious oomycete, P. infestans.