Abstract
Pierce’s disease (PD) is a significant threat to grape cultivation and industry. The disease caused by bacterium Xylella fastidiosa clogs xylem vessels resulting in wilting of the plant. PD-tolerant grape genotypes are believed to produce certain novel components in xylem tissue that help them to combat invading pathogens. Research has been aimed at characterizing the uniquely expressed xylem proteins by PD-tolerant genotypes. The objectives were to i) compare and characterize Vitis xylem proteins differentially expressed in PD-tolerant and PD-susceptible cultivars and, ii) identify xylem proteins uniquely expressed in PD-tolerant genotypes. A high throughput two-dimensional gel electrophoresis of xylem proteins from three Vitis species identified more than 200 proteins with pls 3.0 to 9.0 and molecular weights of 20 to 75 kDa. The differentially expressed proteins were then excised and analyzed with MALDI/TOF mass spectrometer. The mass spectra were collected and protein identification was performed against the Viridiplantae database using Matrix Science algorithm. Proteins were mapped to the universal protein resource to study gene ontology. Comparative analysis of the xylem proteome of three species indicated the highest number of proteins in muscadine grape, followed by Florida hybrid bunch and bunch grape. These proteins were all associated with disease resistance, energy metabolism, protein processing and degradation, biosynthesis, stress related functions, cell wall biogenesis, signal transduction, and ROS detoxification. Furthermore, β-1, 3-glucanase, 10-deacetyl baccatin III-10-O-acetyl transferase-like, COP9, and aspartyl protease nepenthesin precursor proteins were found to be uniquely expressed in PD-tolerant muscadine grape, while they are absent in PD-susceptible bunch grape. Data suggests that muscadine and Florida hybrid bunch grapes express novel proteins in xylem to overcome pathogen attack while bunch grape lacks this capability, making them susceptible to PD.
Highlights
Vitis is a genus of about 60 species of vining plants in the family Vitaceae, mostly is dominated by bunch (Vitis vinifera L., V. labrusca L., and other Vitis spp.) grape for commercial grape cultivation
Our results suggests that muscadine and Florida hybrid bunch grape genotypes express certain novel proteins while bunch grape lacks these proteins, making the latter, susceptible to Pierce’s disease (PD)
The differences observed in the relative amounts of various proteins among the three Vitis species suggested that these variations might contribute to grape plant’s unique tolerance characteristics to biotic and abiotic stresses
Summary
Vitis (grapevines) is a genus of about 60 species of vining plants in the family Vitaceae, mostly is dominated by bunch (Vitis vinifera L., V. labrusca L., and other Vitis spp.) grape for commercial grape cultivation. Local PD-tolerant grape cultivars were hybridized with viniferas to develop new varieties of grape, known as Florida hybrid bunch (FH), which is tolerant to PD [4]. Their tolerance level varies compared to muscadine (whose tolerance remains stable) as the hybrids contain V. vinifera, a PDsusceptible species in their parentage. Most commercial genotypes of grapevine are susceptible to PD, many wild Vitis genotypes and some hybrids of grapevine have shown strong PD resistance in greenhouse evaluations [5]
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