Alteration of some defense-related genes expression in Nicotiana benthamiana leaves in response to Potato virus A HC-Pro silencing suppressor

The role of autophagy and hormones in plant defense against viruses has been proven. To extend our understanding for the possible role of Potato virus A HC-Pro (PVA HC-Pro) suppressor protein in defense mechanisms, we investigated the effect of PVA HC-Pro on expression of some important genes involved in these pathways. 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 syringe infiltrated into the abaxial side of N. benthamiana leaves. The expression of some genes involved in autophagy process, SA and JA pathways were measured at 5 days post infiltration in response to PVA HC-Pro using qRT-PCR technique. The expression level of ATG6, ATG2 and ATG7 was increased in response to PVA HC-Pro with 5.89, 7.3 and 7.6-fold respectively, when compared with their counterparts in infiltrated leaves with empty plasmid (EP) (control). While, transcript level of Argonaute1 (AGO1), a key component of RNA-induced silencing complex (RISC) was decreased with 1.36-fold lower than the level of AGO1 in infiltrated leaves without PVA HC-Pro. Additionally, the expression of the SA and JA upstream genes, ICS1 and OPR3 was increased in PVA HC-Pro with 10.8, 7.76-fold respectively, greater than the level of genes in infiltrated leaves with EP. The transcript levels of SA (NPR1 and PR1), were found to be upregulated in PVA HC-Pro with 2.31, 2.64-fold respectively, more than the accumulation level of genes in infiltrated leaves with EP. While, JA (COI1 and PDF1.2) downstream genes was upregulated in response to PVA HC-Pro with 1.93, 2.69-fold respectively, more than the accumulation level of genes in infiltrated leaves with EP. Results of this study indicated that PVA HC-Pro can alter the expression of autophagy, SA and JA signaling pathway-related genes in N. benthamiana host plant. These findings suggest the involvement of these genes in defense responses of N. benthamiana against PVA HC-Pro that might be considered in plant breeding programs to control viruses.

Keywords:

Gene Silencing , ISR , Potyvirus