Upregulation of miR395 which Targets ATP Sulfurylase and Sulfate Transporter Facilitates Sulfur Enhanced Defence after Hibiscus chlorotic ringspot virus Infection

Previous results showed that interaction of Hibiscus chlorotic ringspot virus (HCRSV) coat protein (CP) and sulfite oxidase (SO) triggers sulfur enhanced defence (SED). MicroRNA395 (miR395), which targets genes ATP sulfurylase (ATPS) and sulfate transporter (SULTR), is the only reported miRNA to be involved in the sulfur metabolism pathway. ATPS and SULTR are two enzymes involved in producing glutathione and transporting sulfate, respectively, in the SED pathway. Hibiscus cannabinus L. (kenaf) was used as an experimental host for studies of HCRSV. In this study, we investigated the correlation of miR395 and its target genes ATPS and SULTR in HCRSV-infected kenaf within 30 days. SULTR showed a stronger negative correlation with miR395 as compared to ATPS after HCRSV infection. Since our previous results showed an upregulation of SO after HCRSV infection, SO overexpression and silencing experiments were carried out to evaluate the effects of SO on the SED effect using agroinfiltration. The miR395 and its target genes ATPS and SULTR were found to be upregulated or downregulated when SO was overexpressed or silenced, respectively. Therefore, this study demonstrated that upregulation of ATPS and SULTR, which are the consequences of SO accumulation facilitates the SED effect. This study contributes to a better understanding of the involvement of the SED pathway in virus infection. (210 words)