Ribosome profiles and riboproteomes of healthy and potato virus A and Agrobacterium -infected Nicotiana benthamiana plants.

Nicotiana benthamiana is an important model plant for plant-microbe interaction studies. Here we compared ribosome profiles and riboproteomes of healthy and infected N. benthamiana plants. We affinity-purified ribosomes from transgenic leaves having FLAG-tagged ribosomal large subunit protein RPL18B of Arabidopsis thaliana incorporated to N. benthamiana ribosomes. Purifications were made from healthy plants and plants that were infiltrated with Agrobacterium tumefaciens carrying infectious cDNA of potato virus A (PVA) or firefly luciferase gene, referred here as PVA- or Agrobacterium -infected plants. Plants encode a number of paralogous ribosomal-proteins (r-proteins). N. benthamiana riboproteome revealed ~6600 r-protein hits representing 424 distinct r-proteins that were members of 71 of the expected 81 r-protein families. The data indicated that N. benthamiana ribosomes are heterogeneous in their r-protein composition. In PVA -infected plants the number of identified r-protein paralogs was lower than in the Agrobacterium- infected or healthy plants. A. tumefaciens proteins did not associate with ribosomes, whereas ribosomes from PVA -infected plants co-purified with viral cylindrical inclusion protein and helper component proteinase, reinforcing their possible role in protein synthesis during virus infection. In addition, viral NIa protease-VPg, RNA polymerase NIb, and coat protein were occasionally detected. Infection did neither affect the proportions of ribosomal subunits nor the monosome to polysome ratio, suggesting that no overall alteration in the translational activity took place upon infection with these pathogens. The riboproteomic data of healthy and pathogen-infected N. benthamiana will be useful for studies on the specific use of r-protein paralogs to control translation in infected plants. This article is protected by copyright. All rights reserved.