# Tetraspanin SfCD9 as a Key Membrane Binding Factor of SRBSDV P10 Facilitates Viral Entry Into Sogatella furcifera Midgut Epithelial Cells via Clathrin‐Mediated Endocytosis

## TL;DR

This study identifies SfCD9 as a key protein that helps a virus enter the gut cells of a rice pest, offering a potential target to stop virus spread.

## Contribution

The study reveals SfCD9 as a novel membrane binding factor for SRBSDV entry via clathrin-mediated endocytosis in Sogatella furcifera.

## Key findings

- SRBSDV P10 interacts with SfCD9 to enter midgut epithelial and haemolymph cells of S. furcifera.
- Knockdown of SfCD9 or anti-SfCD9 antibody delivery inhibits SRBSDV invasion in S. furcifera.
- SRBSDV can only enter SfCD9-expressing Sf9 cells, not wild-type cells.

## Abstract

Southern rice black‐streaked dwarf virus (SRBSDV), transmitted by
Sogatella furcifera
, causes significant rice yield losses in Asia. So far, the mechanism by which SRBSDV traverses the midgut barrier to establish infection in
S. furcifera
midgut epithelial cells remains unknown. Here, we show that SRBSDV P10, the major outer capsid protein, enters
S. furcifera
midgut epithelial and haemolymph cells through interacting with the tetraspanin SfCD9 highly expressed in midgut and haemolymph cells. SfCD9 co‐localises with SRBSDV P10 and relocates it from the endoplasmic reticulum (ER) to the cytomembrane of co‐expressing Sf9 cells. SfCD9 localises on the cell membrane and in the cytoplasm in nonviruliferous
S. furcifera
midgut epithelial cells. SRBSDV P10 and SfCD9 colocalised on the midgut epithelial cell membrane of viruliferous
S. furcifera
at 2 days post‐virus feeding (dpvf), and predominantly colocalised in epithelial cell cytoplasm at 6 dpvf. Knockdown of SfCD9 or oral delivery of the anti‐SfCD9 antibody significantly inhibited SRBSDV invasion in
S. furcifera
. SRBSDV from infected rice crude extracts can enter SfCD9‐expressing Sf9 cells, but not wild‐type Sf9 cells. SfCD9 serves as a key membrane binding factor for SRBSDV entry into vector midgut epithelial cells via clathrin‐mediated endocytosis. Collectively, these findings offer valuable insights into SRBSDV transmission and identify SfCD9 as a potential target to disrupt viral transmission.

Tetraspanin SfCD9 as a key membrane binding factor of SRBSDV P10 facilitates viral entry into
Sogatella furcifera
midgut epithelial cells via clathrin‐mediated endocytosis.