RNAi-mediated silencing of CYP4G15 correlates with altered transmission of barley yellow dwarf virus in Sitobion avenae (Fabricius)

Abstract

Insect-borne plant viruses have emerged as major threats to crop production, and the genes of vector insects involved in viral transmission are crucial for effective viral control. However, few studies have identified and functionally validated these genes. A previous study suggested that the aphid protein CYP4G15 interacts with the barley yellow dwarf virus (BYDV; Luteoviridae: Luteovirus) virion in vitro. We hypothesized that the ability of vector aphids to transmit BYDV would be correlated with CYP4G15. To test this hypothesis, we first cloned and analyzed SaCYP4G15 in grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), and then examined the expression levels of SaCYP4G15 in S. avenae during the acquisition accession periods (AAPs) and inoculation accession periods (IAPs) of the transmission of the BYDV species PAV (BYDV-PAV). Finally, the role of SaCYP4G15 in the acquisition, retention, and transmission of BYDV-PAV was evaluated by the RNA interference (RNAi) method. The results showed that 1) the coding DNA sequence of SaCYP4G15 was 1701 bp, which corresponds to 566 amino acids, and a transmembrane domain is anticipated to be present at the N-terminus; 2) the expression level of SaCYP4G15 in S. avenae was notably up-regulated in both the AAPs and IAPs of BDYV-PAV transmission; and 3) after knockdown SaCYP4G15, the relative amount of BYDV-PAV in S. avenae decreased during AAPs and increased during IAPs. Additionally, the transmission efficiency of BYDV-PAV during IAPs decreased. These results indicated that SaCYP4G15 in S. avenae correlated with changes in BYDV-PAV transmission by increasing acquisition and transmission efficiency, while decreasing retention. This study extends our knowledge of the interaction between Luteoviridae and vector aphids and suggests that the SaCYP4G15 gene could be a potential target for RNAi-based BYDV control.