Proteomics of Papaya ringspot virus-Infected Papaya Leaves

Abstract

The Papaya ringspot virus (PRSV) causes severe economic losses in both papaya and cucurbits throughout the tropical and subtropical regions. An understanding of the interaction between the papaya plant and PRSV can help to improve papaya production. The protein profi les of virus-infected and healthy papaya leaves were compared by two-dimensional polyacrylamide gel electrophoresis. Among the observed 490 protein spots, 227 were identifi ed using matrix-assisted laser desorption/ionizationtime of fl ight mass spectrometry and liquid chromatography-mass spectrometry. Forty-three proteins were found to be similar to those identifi ed in the Papaya EST and NCBI nr databases. They play roles in the areas of: photosynthesis (14%), photorespiration (5%), metabolism (20%), gene and biosynthesis (10%), defence related (7%), stress response (5%), signal transduction (10%), and unknown processes (29%). Spot intensity and transcription levels determined by real-time polymerase chain reaction showed ribulose-1, 5-bisphosphate carboxylase, Rieske protein ubiquinol cytochome C and chlorophyll A/B binding were down-regulated in infected plants. On the other hand, ubiquitin-like modifi ers, vascular processing enzyme and germin-like protein were up-regulated in infected plants at transcription and translation levels. The results showed the novel virus-responding mechanism of the papaya plant that might be essential for developing viral-tolerant papaya in the agricultural industries.