Arabidopsis ALA1 and ALA2 Mediate RNAi-Based Antiviral Immunity.

Biyun Zhu,Tiancong Qi,Susheng Song,Hongshan Jiang,Gang Xu,Shuifang Zhu,Daoxin Xie,Hua Gao,Dewei Wu

doi:10.3389/fpls.2017.00422

Abstract

RNA intereferencing (RNAi) pathway regulates antiviral immunity and mediates plant growth and development. Despite considerable research efforts, a few components in RNAi pathway have been revealed, including ARGONAUTEs (AGOs), DICER-LIKEs (DCLs), RNA-dependent RNA polymerase 1 and 6 (RDR1/6), and ALTERED MERISTEM PROGRAM 1 (AMP1). In this study, we performed a forward genetic screening for enhancers of rdr6 via inoculation of CMV2aTΔ2b, a 2b-deficient Cucumber Mosaic Virus that is unable to suppress RNAi-mediated antiviral immunity. We uncover that the membrane-localized flippase Aminophospholipid ATPase 1 (ALA1) cooperates with RDR6 and RDR1 to promote antiviral immunity and regulate fertility in Arabidopsis. Moreover, we find that ALA2, a homolog of ALA1, also participates in antiviral immunity. Our findings suggest that ALA1 and ALA2 act as novel components in the RNAi pathway and function additively with RDR1 and RDR6 to mediate RNAi-based antiviral immunity and plant development.

Highlights

RNA interference (RNAi) mediates plant defense against virus infections (Ding et al, 2004; Incarbone and Dunoyer, 2013; Martinez de Alba et al, 2013)
We show that Aminophospholipid ATPase 1 (ALA1) and ALA2 act additively with RDR1 and RDR6 to mediate RNAi-mediated antiviral immunity and development
We generated M2 population of ethyl methanesulfonate (EMS)-mutagenized rdr6, and inoculated M2 with CMV2aT 2b to identify mutants that enhanced the susceptibility to CMV2aT 2b in rdr6, and utilized whole genome sequencing to assist mapping and cloning of ENOR loci (Figure 1A)

Summary

INTRODUCTION

RNA interference (RNAi) mediates plant defense against virus infections (Ding et al, 2004; Incarbone and Dunoyer, 2013; Martinez de Alba et al, 2013). Cucumber Mosaic Virus (CMV) utilizes the VSR protein 2b (Zhang et al, 2006; DiazPendon et al, 2007) to suppress host RNAi-based antiviral immunity and causes severe pathogenic responses in wild-type Arabidopsis, while CMV2aT 2b, a CMV mutant without expression of 2b protein, is unable to cause any obvious viral symptoms in wild-type and the single mutants of RDR1 or RDR6, but is able to cause severe pathogenic responses in the RNAi-deficient double mutant rdr rdr (Wang et al, 2010). There are 12 Arabidopsis thaliana ALAs in the IV subfamily of ATPases that control plant development or tolerance to temperature. ALA1/2 Mediate RNAi-Based Antiviral Immunity stresses (Lopez-Marques et al, 2014). We show that ALA1 and ALA2 act additively with RDR1 and RDR6 to mediate RNAi-mediated antiviral immunity and development.

MATERIALS AND METHODS

RESULTS

DISCUSSION