Xylella fastidiosa: role of exoenzymes (proteases, cellulases, pectate lyases) and adhesion (in the plant and insect vector) in pathogenicity

Abstract

The project (classified as a "projeto temático") involves a group of 8 leading scientists with different scientific backgrounds from 4 institutions (ESALQ/USP, lAC, I. Butantan, UNICAMP) and fits well into the objectives of the program "Functional genome of Xylella fastidiosa". The information generated by nucleotide sequence from the Genome Project will be used in this project with the main objective of finding out the biological function of identified genes having as result the understanding of the pathogenicity factors of Xylella as well as the possibility of developing approaches for controlling the disease. The proposed project is directed towards the comprehension of the bacterium pathogenicity mechanisms by looking at extra-cellular enzymes such as proteases, cellulases and pectate Iyases and the adhesion of the cells to the host plant and insect vector. Based upon a search for homologies between sequenced pathogenicity genes from other organisms in the Genebank and the Xylella nucleotide sequence, we found Xylella cosmids containing genes sharing high homologies with genes from other bacteria for proteases, cellulases, pectate Iyases and molecules involved in the adhesion phenomena. Based upon this information, which will be updated as the sequencing of Xylella genome advances, the genes concerned to this study will be cloned in Escherichia colli cells, as a vector for gene expression. Proteins and adhesion molecules encoded by these genes will be isolated, purified, characterized and the biological role determined through bioassays either by using the plant tissue or the insect vector. In addition, the biologically significant molecules found will be used for the production of antibodies for immunolocalization assays. Finally, these antibodies as well as some known commercially available substances will be used as an attempt to block the biological activity of the molecules possibly leading to the control of the eve disease. (AU)