Silencing of Putative Plasmodesmata-Associated Genes PDLP and SRC2 Reveals Their Differential Involvement during Plant Infection with Cucumber Mosaic Virus

Plant viruses utilize a subset of host plasmodesmata-associated proteins to establish infection in plants. In the present study, we aimed to understand the role of two plant genes, one encoding a putative plasmodesma located protein (PDLP) and a homolog of soybean gene regulated by cold 2 protein (SRC2) during Cucumber mosaic virus (CMV) infection. Virus-induced gene silencing (VIGS) was used to silence <i>PDLP</i> and <i>SRC2</i> genes in <i>Nicotiana benthamiana</i> and in two related solanaceous plants, <i>N. tabacum</i> and <i>Capsicum chinense</i> Jacq. (Bhut Jolokia). Up to 50% downregulation in the expression of the <i>PDLP</i> gene using the TRV2-<i>PDLP</i> VIGS construct was observed in <i>N. benthamiana</i> and <i>N. tabacum</i> while, using the same gene construct, 30% downregulation of the target mRNA was observed in <i>C. chinense</i>. Similarly, using the TRV2-<i>SRC2</i> VIGS construct, a 60% downregulation of the <i>SRC2</i> mRNA was observed in <i>N. benthamiana</i>, <i>N. tabacum</i>, and a 40% downregulation in <i>C. chinense</i> as confirmed by qRT-PCR analysis. Downregulation of the <i>PDLP</i> gene in <i>N. benthamiana</i> resulted in delayed symptom appearance up to 7-12 days post inoculation with reduced CMV accumulation compared to the control plants expressing TRV2-<i>eGFP</i>. In contrast, <i>SRC2</i>-silenced plants showed enhanced susceptibility to CMV infection compared to the control plants. Our data suggest that the <i>PDLP</i> gene might facilitate infection of CMV, thus being a susceptibility factor, while the <i>SRC2</i> gene could play a role in resistance to CMV infection in <i>N. benthamiana</i>.