Identification and characterization of xylem components associated with Pierce’s disease tolerance in grape

Abstract

Pierce’s disease (PD) is a destructive bacterial disease of grapes caused by Xylella fastidiosa, which is xylem confined. PD-tolerant grape genotypes are believed to produce certain novel components in xylem tissue that help them combat invading pathogen. However, the nature and identity of these components is unknown. This research was aimed at identifying and characterizing the uniquely expressed xylem proteins by PD-tolerant genotypes. The objectives are to 1) develop xylem proteome fi ngerprint for commercially important Vitis spp.; 2) compare and characterize Vitis xylem proteins; and 3) identify xylem proteins uniquely expressed in PD-tolerant genotypes. The two-dimensional electrophoresis resolved xylem proteins into more than 200 polypeptides with pIs between 3.0 to 9.0 and molecular weight (Mr) 20 to 75 kDa. Comparative analysis of xylem proteome showed that highest amount of protein is present in muscadine, moderate amount in Florida hybrid bunch, and lowest in bunch grape. Further, eight proteins were found to be uniquely expressed in PD-tolerant genotypes while they are absent in PD-susceptible genotypes. These data suggest that V. rotundifolia and Florida hybrid bunch grape genotypes express novel proteins in xylem to overcome pathogen attack while V. vinifera lacks this capability, which makes them susceptible to PD.