Sequence/structural analysis of xylem proteome emphasizes pathogenesis-related proteins, chitinases andβ-1, 3-glucanases as key players in grapevine defense againstXylella fastidiosa

Abstract

Background. Xylella fastidiosa, the causative agent of various plant diseases including Pierce’s disease in the US, and Citrus Variegated Chlorosis in Brazil, remains a continual source of concern and economic losses, especially since almost all commercial varieties are sensitive to this Gammaproteobacteria. Differential expression of proteins in infected tissue is an established methodology to identify key elements involved in plant defense pathways.Methods. In the current work, we developed a methodology named CHURNER that emphasizes relevant protein functions from proteomic data, based on identification of proteins with similar structures that do not necessarily have sequence homology. Such clustering emphasizes protein functions which have multiple copies that are up/down-regulated, and highlights similar proteins which are differentially regulated. As a working example we present proteomic data enumerating differentially expressed proteins in xylem sap from grapevines that were infected with X. fastidiosa.Results. Analysis of this data by CHURNER highlighted pathogenesis related PR-1 proteins, reinforcing this as the foremost protein function in xylem sap involved in the grapevine defense response to X. fastidiosa. β-1, 3-glucanase, which has both anti-microbial and anti-fungal activities, is also up-regulated. Simultaneously, chitinases are found to be both up and down-regulated by CHURNER, and thus the net gain of this protein function loses its significance in the defense response.Discussion. We demonstrate how structural data can be incorporated in the pipeline of proteomic data analysis prior to making inferences on the importance of individual proteins to plant defense mechanisms. We expect CHURNER to be applicable to any proteomic data set.

Molecular Profiling of Pierce’s Disease Outlines the Response Circuitry of Vitis vinifera to Xylella fastidiosa Infection

“…Given the xylem-dwelling characteristic of the pathogen, deep within the plant, and its ability to form biofilms and secrete virulence factors, pathogen clearance is not achieved in susceptible hosts despite the array of responses observed, including PR proteins and phytoalexins. Our data expand the set of PR proteins previously detected in the xylem sap of X. fastidiosa -infected grapevines ( Chakraborty et al, 2016 ) further reinforcing their importance in the defense response. Though fastidious in growth, X. fastidiosa can actively migrate with and against xylem sap flow ( Meng et al, 2005 ) and colonize the plant systemically, overcoming host strategies to halt pathogen proliferation.…”

Lipopolysaccharide O-antigen delays plant innate immune recognition of Xylella fastidiosa

“…Specifically, there were three Class III peroxidases ( VIT_18s0001g06840 ; VIT_18s0001g06850 ; VIT_18s0001g06890 ). These peroxidases accumulate in abundance in xylem sap during colonization by vascular pathogens 4 , 32 . Their functions include specific roles in defense against pathogen infection, such as enhanced production of ROS (as signal mediators and antimicrobial agents) and enhanced production of phytoalexins 33 .…”

YeATSAM analysis of the walnut and chickpea transcriptome reveals key genes undetected by current annotation tools

“…This pathway is over-expressed upon osmotic stress and pathogen attack ( Attila et al , 2008; González-Candelas et al , 2010), provides resistance in lettuce, sunflower and transgenic tobacco by generating anti-microbial compounds ( Custers et al , 2004), and has unknown functions at specific developmental stages in Arabidopsis ( Irshad et al , 2008; Pagnussat et al , 2005). Moreover, it is expressed in floral nectar (Nectarin V, Nt BBE) ( Carter & Thornburg, 2004) and roots of tobacco ( Kajikawa et al , 2011), and in xylem sap of cabbage ( Ligat et al , 2011) and grapevine ( Chakraborty et al , 2016b). Nt BBE was constitutively expressed in the Phytophthora infestans -resistant potato genotype SW93-1015 ( Ali et al , 2012).…”