COMPARATIVE PROTEIN EXPRESSION OF TWO PAPAYA CULTIVARS SHOWING A DIFFERENTIAL RESPONSE TO THE ROOT-ROT PATHOGEN PHYTOPHTHORA PALMIVORA.

Among the Hawaiian papaya (Carica papaya L.) cultivars, 'Kamiya' is more tolerant to Phytophthora palmivora than 'SunUp'. To understand the molecular basis for the difference between these two cultivars, their protein profiles cultivars were investigated by two-dimensional (2D) electrophoresis. Two hundred and fifty expressed protein spots were compared between 'Kamiya' and 'SunUp' on triplicate 2D gels. Twentyfive out of 28 differentially-expressed spots were successfully identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and three differentially migrating spots were identified as a single protein. Among the 15 proteins up-regulated 2-fold or higher in 'Kamiya', nine were related to plant disease resistance and defense response, while among the 8 proteins up-regulated 2 fold or more in 'SunUp', one was involved in disease and defense. Six differentially expressed proteins were further confirmed by semi-quantitative RT-PCR. Identified proteins were involved in at least five categories of plant defense or disease resistance: jasmonic acid (JA)-dependent pathway, ATP binding cassette (ABC) transporters, plant brassinolide hormone, abscisic acid (ABA)/reactive oxygen species (ROS) plant defense pathway, and transcription regulation. Our results infer that tolerant 'Kamiya' possesses various defense mechanisms against P. palmivora. [ABSTRACT FROM AUTHOR]