Recently, researchers at State Key Laboratory of Plant Diseases and Insect Pests, Institute of Plant Protection of CAAS have published a research paper on Molecular Plant about new findings of the novel tobacco RING E3 ligase NtRFP1-mediated defense against geminivirus-encoded βC1, a pathogenicity determinant encoded by the Tomato yellow leaf curl China virus associated betasatellite.

Geminiviruses are a group of circular, single-stranded DNA viruses that infect a broad variety of plants and cause considerable loss in many economically important crops worldwide. Geminiviruses are obligate molecular parasites that encode relatively few proteins and are exclusively dependent on host resources for multiplication and movement. To combat attack, plant hosts have evolved diverse innate defense mechanisms to defend against virus invasion and attenuate development of disease symptoms. Therefore, elucidation of host-geminivirus interactions will advance our understanding of virulence functions, as well as surveillance mechanisms that have evolved to protect plants from infection.

The new results revealed that βC1 interacts with NtRFP1 and induces the expression of NtRFP1. In vitro ubiquitination assays showed that NtRFP1 is a functional E3 ubiquitin ligase that catalyzed βC1 ubiquitination and degradation by the 26S proteasome. In addition, study showed that NtRFP1 attenuates βC1-induced symptoms by promoting βC1 degradation. After viral infection, plants overexpressing NtRFP1 developed attenuated symptoms, and plants silenced for NtRFP1 expression had severe symptoms. The findings suggest that NtRFP1 is part of the host defense system and can attenuate disease symptoms via ubiquitination and degradation of βC1 through the ubiquitin/26S proteasome system.