Palmitoylation Is Indispensable for Remorin to Restrict Tobacco Mosaic Virus Cell-to-Cell Movement in Nicotiana benthamiana

A novel cellular factor of Nicotiana benthamiana susceptibility to tobamovirus infection

Viral infection, which entails synthesis of viral proteins and active reproduction of the viral genome, effects significant changes in the functions of many intracellular systems in plants. Along with these processes, a virus has to suppress cellular defense to create favorable conditions for its successful systemic spread in a plant. The virus exploits various cellular factors of a permissive host modulating its metabolism as well as local and systemic transport of macromolecules and photoassimilates. The Nicotiana benthamiana stress-induced gene encoding Kunitz peptidase inhibitor-like protein (KPILP) has recently been shown to be involved in chloroplast retrograde signaling regulation and stimulation of intercellular transport of macromolecules. In this paper we demonstrate the key role of KPILP in the development of tobamovius infection. Systemic infection of N. benthamiana plants with tobacco mosaic virus (TMV) or the closely related crucifer-infecting tobamovirus (crTMV) induces a drastic increase in KPILP mRNA accumulation. KPILP knockdown significantly reduces the efficiency of TMV and crTMV intercellular transport and reproduction. Plants with KPILP silencing become partially resistant to tobamovirus infection. Therefore, KPILP could be regarded as a novel proviral factor in the development of TMV and crTMV infection in N. benthamiana plants.

Comprehensive Analysis of Ubiquitome Changes in Nicotiana benthamiana after Rice Stripe Virus Infection

Rice stripe virus (RSV) is one of the most devastating viruses affecting rice production. During virus infection, ubiquitination plays an important role in the dynamic regulation of host defenses. We combined the ubiquitomics approach with the label-free quantitation proteomics approach to investigate potential ubiquitination status changes of Nicotiana benthamiana infected with RSV. Bioinformatics analyses were performed to elucidate potential associations between proteins with differentially ubiquitinated sites (DUSs) and various cellular components/pathways during virus infection. In total, 399 DUSs in 313 proteins were identified and quantified, among them 244 ubiquitinated lysine (Kub) sites in 186 proteins were up-regulated and 155 Kub sites in 127 proteins were down-regulated at 10 days after RSV infection. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated that proteins with up-regulated Kub sites were significantly enriched in the ribosome. Silencing of 3-isopropylmalate dehydratase large subunit through virus-induced gene silencing delayed RSV infection, while silencing of mRNA-decapping enzyme-like protein promoted RSV symptom in the late stage of infection. Moreover, ubiquitination was observed in all seven RSV-encoded proteins. Our study supplied the comprehensive analysis of the ubiquitination changes in N. benthamiana after RSV infection, which is helpful for understanding RSV pathogenesis and RSV-host interactions.