Small interfering RNA pathway modulates initial XXXX in the midgut epithelium of insect after ingestion of virus.

@entity30416 @entity62735 @entity1800 @entity579
UNASSIGNED: Numerous viruses are transmitted in a persistent manner by insect vectors. Persistent viruses establish their initial infection in the midgut epithelium, from where they disseminate to the midgut visceral muscles. Although propagation of viruses in insect vectors can be controlled by the small interfering RNA (siRNA) antiviral pathway, whether the siRNA pathway can control viral dissemination from the midgut epithelium is unknown. A @entity579 virus ( @entity30416 , SRBSDV) is restricted its infection in the midgut epithelium of its incompetent vector ( @entity62735 , SBPH). Here, we showed that the siRNA pathway was triggered by SRBSDV infection in the continuous cultured cells derived from SBPH and in the midgut of the intact insect. Knockdown of the expression of the core component Dicer-2 of siRNA pathway due to RNA interference strongly increased the propagation ability of SRBSDV in the continuous SBPH cultured cells and in the midgut epithelium, allowing viral titers in the midgut epithelium to reach a certain threshold (1.99 * 10(9) copies of SRBSDV P10 gene/ g midgut RNA) needed for viral dissemination into the SBPH midgut muscles. Our results thus represent the first elucidation of the threshold for viral dissemination from the insect midgut epithelium. The silencing of Dicer-2 further facilitated the transmission of SRBSDV into @entity579 plants by SBPHs. Taken together, our results revealed a new finding that the siRNA pathway can control the initial infection of a virus in the insect midgut epithelium, which finally affected vector competence of a virus. IMPORTANCE: Many viral pathogens that cause significant global health and agricultural problems are transmitted via insect vectors. The first bottleneck for @entity1800 , the midgut epithelium, is a principal determinant of the ability of an insect species to transmit a virus. @entity30416 (SRBSDV) is exclusively restricted to the midgut epithelium of the incompetent vector @entity62735 (SBPH). Here, we show that silencing of the core component Dicer-2 of siRNA pathway increased viral titers in the midgut epithelium past a certain threshold (1.99 * 10(9) copies of SRBSDV P10 gene/ g midgut RNA) for viral dissemination into the midgut muscles, then into the salivary glands, allowing the SBPH to become a competent vector of SRBSDV. This result is the first evidence of a direct role of the siRNA antiviral pathway in controlling viral dissemination from the midgut epithelium and affecting vector competence of a virus.
