Location: Produce Safety and Microbiology ResearchTitle: Identification of protein biomarkers of Xylella fastidiosa using MALDI-TOF-TOF-MS/MS and top-down proteomic analysis
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/7/2022
Publication Date: N/A
Technical Abstract: Xylella fastidiosa is an aerobic gram-negative bacterium that causes Pierce’s Disease in viticulture resulting in its destruction. X. fastidiosa is transmitted by sharpshooter leafhoppers (e.g. Glassy-winged sharpshooter). A number of X. fastidiosa strains have been genomically sequenced. However, only a few proteomic studies have been performed on this plant pathogen. Using MALDI-TOF-TOF-MS/MS and top-down proteomic analysis, we have identified several highly conserved proteins whose sequences are identical in two genomically sequenced X. fastidiosa strains (M23 and Stag’s Leap) both of which were isolated in California. In addition, we have identified an outer membrane/hypothetical protein whose sequence differs between these strains and which shows variable sequence truncation at the N-terminus. Samples were analyzed using a 4800 MALDI-TOF-TOF mass spectrometer (Sciex). MS and MS/MS data were analyzed using software developed in-house to scan in silico protein sequences derived from whole genome sequencing (WGS). Software identifications were confirmed by manual inspection. Four highly conserved proteins were identified: two cold-shock/DNA-binding proteins, 10 kDa chaperonin protein GroES and 50S ribosomal protein L33. The protein sequences were identical in both X. fastidiosa strains. The N-terminal methionine was removed consistent with the penultimate residue rule for bacterial proteins. In addition, we identified an outer membrane/hypothetical protein (OMP/Hypo) whose sequence differed significantly between the two strains and also exhibited variable truncation of its sequence from the N-terminus. This variable sequence truncation was not observed for other identified proteins suggesting that this unusual truncation may be intrinsic to this protein structure/function. Finally, the OMP/Hypo protein displayed a number of alanine residue repeats (i.e. AA, AAA, AAAA, AAAAA, etc.) distributed across its primary sequence.