Altered expression of autophagy-related genes in Nicotiana benthamiana plants in response to Potato virus A HC-Pro silencing suppressor

Accumulating data have revealed the role of autophagy in virus-induced RNA silencing via viral RNA silencing suppressor activity. To extend our understanding for the possible role of Potato virus A-HC-Pro (PVA-HC-Pro) suppressor protein in autophagy process, we investigated the effect of PVA-HC-Pro on expression of some important genes involved in autophagy. The cDNA of ORF PVA HC-Pro was cloned in pGWB17 vector with a C-terminal myc tag and N-terminal 35S promoter using Gateway technology. Agrobacterium cultures harboring PVA-HC-Pro were infiltrated into the abaxial side of N. benthamiana leaves. The expression of ATG6, ATG2, ATG7 and AGO1 genes were measured at 5 days post infiltration in response to PVA-HC-Pro using qRT-PCR technique. PVA HC-Pro as a suppressor of RNA silencing increased the expression level of ATG6, ATG2 and ATG7 5.89, 7.3 and 7.6 fold, respectively, compared to corresponding values in leaves infiltrated with empty plasmid (EP) as a control. In contrast, the transcript level of Argonaute1 (AGO1), a key component of RNA-induced silencing complex (RISC), was decreased by 1.36-fold compared to the level of AGO1in infiltrated leaves without PVA-HC-Pro. Results of this study indicated that PVA HC-Pro can alter the expression of autophagy related genes in N. benthamiana plant. These findings suggest the involvement of ATG6, ATG2, ATG7 and AGO1 in defense responses of N. benthamiana against PVA-HC-Pro, which might be considered in plant breeding programs as a novel approach to the control of plant viruses.