Investigating the role of miRNA160 and miRNA166 in defence response of potato

Abstract

To combat pathogen infection, plants have developed an immune response to protect them at the site of infection and prime the whole plant through systemic acquired resistance (SAR). Recently, numerous microRNAs have been shown to play a crucial role in plant’s defence response such as Arabidopsis, rice, soybean, potato and wheat. A previous study from our lab demonstrated the importance of miRNA160 in regulating both local and systemic defence response in potato upon Phytophthora infestans infection. miRNA160 was demonstrated to be involved in elicitation of SAR response, however, the mechanistic basis was not clear. In this study, we attempted to further elucidate the role of miRNA160 and miRNA166 in controlling potato defence response against necrotrophic and hemi-biotrophic pathogens. We show that StARF16 (a development associated gene and a target of miRNA160), is differentially regulated upon infection. This response was also noticed to be induced upon treatment with defence associated hormone: jasmonic acid & salicylic acid. Our study reveals a novel and a direct regulation of StNPR1 (a defence gene) by StARF16. Furthermore, the application of Glycerol 3 phosphate (G3P, a significant SAR signal) could rescue the compromised SAR phenotype in miRNA160 knockdown (KD) transgenic lines suggesting that KD lines are compromised in G3P accumulation. Additionally, miRNA166 was also differentially regulated in potato upon treatment with P. infestans during early infection, implying that miRNA166 is involved in the PAMP triggered response. The transgenic plants of miR166, miR166 OE and KD, when subjected to SAR assays, showed that KD lines but not OE, failed to establish SAR response and showed differential accumulation of defence and SAR markers. We establish that the miRNA166 target, StICU1 is crucial for the development of SAR response in potato. Overall, this study sheds light on the role of two miRNAs, miRNA160 and miRNA166, in the defence response during potato-pathogen interactions