Dynamic Subcellular Localization, Accumulation, and Interactions of Proteins From Tomato Yellow Leaf Curl China Virus and Its Associated Betasatellite.

Hao Li,Pan Gong,Mingzhen Zhang,Xueping Zhou,Fangfang Li

doi:10.3389/fpls.2020.00840

Abstract

Geminiviruses contain the largest number of species of plant viruses, and cause devastating crop diseases worldwide. The development of resistance to these viruses will require a clear understanding of viral protein function and interactions. Tomato yellow leaf curl China virus (TYLCCNV) is a typical monopartite geminivirus, which is associated with a tomato yellow leaf curl China betasatellite (TYLCCNB) in the field; the complex infection of TYLCCNV/TYLCCNB leads to serious economic losses in solanaceous plants. The functions of each protein encoded by the TYLCCNV/TYLCCNB complex have not yet been examined in a targeted manner. Here, we show the dynamic subcellular localization and accumulation of six viral proteins encoded by TYLCCNV and the βC1 protein encoded by TYLCCNB in plants over time, and analyzed the effect of TYLCCNV or TYLCCNV/TYLCCNB infection on these parameters. The interaction among the seven viral proteins was also tested in this study: C2 acts as a central player in the viral protein interaction network, since it interacts with C3, C4, V2, and βC1. Self-interactions were also found for C1, C2, and V2. Together, the data presented here provide a template for investigating the function of viral proteins with or without viral infection over time, and points at C2 as a pivotal protein potentially playing a central role in the coordination of the viral life cycle.

Highlights

Geminiviruses are a group of plant viruses with single-stranded circular DNA genomes that are encapsidated in twinned viral particles, transmitted by insect vectors and causing devastating crop diseases worldwide
C1, as a replication initiation protein (Rep) involved in the replication of the geminivirus genome in the nucleus, was initially localized in this subcellular compartment, and partially localized outside of the nucleus with decreasing fluorescence intensity over time (Figure 1). We found that both in the protein level and RNA level of Tomato yellow leaf curl China virus (TYLCCNV) C1-yellow fluorescence protein (YFP) decreased from 48 to 96 hpi (Figure 3 and Supplementary Figure S1), suggesting that the expression of C1-YFP is susceptible to both RNA and protein-mediated degradation
C4-YFP was localized at the plasma membrane, and no obvious change was observed in the C4-YFP subcellular localization or C4-YFP protein accumulation over time (Figures 2, 3)

Summary

Introduction

Geminiviruses are a group of plant viruses with single-stranded circular DNA genomes that are encapsidated in twinned viral particles, transmitted by insect vectors and causing devastating crop diseases worldwide. Based on their genome organization, transmission insect vectors, and host range, geminiviruses are divided into nine genera. Tomato yellow leaf curl China virus (TYLCCNV) is a typical monopartite geminivirus, which appears associated with a tomato yellow leaf curl China betasatellite (TYLCCNB) in the field (Cui et al, 2004). Infection by TYLCCNV alone in tobacco or tomato plants fails to induce any obvious symptoms and accumulate less viral DNA (Cui et al, 2004). The functions of βC1 are well characterized (Zhou, 2013; Li et al, 2018a); for example, TYLCCNB βC1 suppresses transcriptional gene silencing (TGS) by inhibiting the activity of S-adenosylhomocysteine hydrolase (SAHH) to restrict the production of S-adenosyl methionine, an essential methyltransferase co-factor (Yang et al, 2011); TYLCCNB βC1 inhibits post-transcriptional gene silencing (PTGS) by up-regulating the expression of an endogenous RNA silencing suppressor, rgs-CaM, which can reduce the transcription of NbRDR6 (Li et al, 2014), and interact with NbSGS3 to guide its autophagic degradation (Li et al, 2017)

Methods

Results

Conclusion