Abstract
Alphasatellites, which encode only a replication-associated protein (alpha-Rep), are frequently found to be non-essential satellite components associated with begomovirus/betasatellite complexes, and their presence can modulate disease symptoms and/or viral DNA accumulation during infection. Our previous study has shown that there are three types of alphasatellites associated with begomovirus/betasatellite complexes in Yunnan province in China and they encode three corresponding types of alpha-Rep proteins. However, the biological functions of alpha-Reps remain poorly understood. In this study, we investigated the biological functions of alpha-Reps in post-transcriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) using 16c and 16-TGS transgenic Nicotiana benthamiana plants. Results showed that all the three types of alpha-Rep proteins were capable of suppressing the PTGS and reversing the TGS. Among them, the alpha-Rep of Y10DNA1 has the strongest PTGS and TGS suppressor activities. We also found that the alpha-Rep proteins were able to increase the accumulation of their helper virus during coinfection. These results suggest that the alpha-Reps may have a role in overcoming host defense, which provides a possible explanation for the selective advantage provided by the association of alphasatellites with begomovirus/betasatellite complexes.
Highlights
Ory of Rice Biology, Institute of Biotechnology, Zhejiang University, Biotechnology and Germplasm Resources Institute, Yunnan Academy of Agricultural Sciences, Key Laboratory of Vector Biology and Pathogen Control of Zhejiang Province, College of Life Sciences, Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China
Our results showed that alpha-replication protein (Rep) are involved in the post-transcriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) in transgenic N. benthamiana 16c and 16-TGS plants
The result showed that Y10alphaRep, Y35alpha-Rep, Y132alpha-Rep, GDarSLA-Rep (Rep encoded by Gossypium darwinii symptomless alphasatellite, GDarSLA), and GMusSLA-Rep (Rep encoded by Gossypium mustelinium symptomless alphasatellite, GMusSLA) display a high sequence similarity
Summary
We found that the alpha-Rep proteins were able to increase the accumulation of their helper virus during coinfection These results suggest that the alpha-Reps may have a role in overcoming host defense, which provides a possible explanation for the selective advantage provided by the association of alphasatellites with begomovirus/betasatellite complexes. Post-transcriptional gene silencing (PTGS), which is initiated by double stranded RNA (dsRNA), is common in plant-virus interactions and is an evolutionarily conserved mechanism that protects host cells against invasive nucleic acids, such as viruses, transposons, and transgenes [4–6]. As a counter to these host defenses, most plant viruses encode proteins that act as suppressors of TGS and PTGS [7], such as Rice stripe virus (RSV) [8], Tobacco etch virus (TEV) [9], Cucumber mosaic virus (CMV) [10] and Cotton leaf curl Multan virus (CLCuMuV) [11].
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