Functional Analysis of <i>BcSNX3</i> in Regulating Resistance to Turnip Mosaic Virus (TuMV) by Autophagy in Pak-choi (<i>Brassica campestris</i> ssp. <i>chinensis</i>)

Abstract

Sorting nexin protein is a class of highly conserved eukaryotic proteins containing the PX domain. Recent studies related to SNX in plants have focused on the regulation of abiotic stress processes, and there are few studies on the involvement of SNX in biological stress processes in plants. In this paper, a YTH assay and BiFC experiments were conducted twice to show that BcSNX3 (Brassica campestris Sorting nexin 3) interacted with CP and VPg of TuMV, and the interaction between BcATG8h (Brassica campestris autophagy-related gene 8h) and BcSNX3 was also found by YTH and BiFC. The colocalization of BcSNX3 and BcATG8b (Brassica campestris autophagy-related gene 8b) revealed BcSNX3 and autophagosome at the same place in the cell. QRT-PCR analysis showed that TuMV infection promotes the expression of BcSNX3, and the overexpression of this gene hinders the expression of autophagy-related genes and facilitates TuMV infection. VIGS was used to repress the expression level of the BcSNX3 gene in pak-choi to further study the function of BcSNX3 in the infection process of TuMV. After inoculation with TuMV, it was found that the accumulation of viral RNA in BcSNX3-gene-silenced plants was significantly less than in control plants. The accumulation of TuMV virus in the Arabidopsis snx3 knockout mutant was also less than in the wild type after TuMV inoculation. These results suggest that TuMV infection facilitates the expression of BcSNX3, and this gene may promote virus infection by inhibiting autophagy degradation of the virus and interacting with the CP and VPg of the virus. These results lay the foundation for the TuMV resistance breeding of pak-choi.

Keywords

• pak-choi
• TuMV
• autophagy
• BcSNX3