Application of Tn5 derivatives in understanding rice - xanthomonas oryzae interaction

Abstract

Xanthomonas oryzae pv. oryzae is the causal agent of bacterial leaf blight, a newlineserious disease of rice. The disease occurs in many rice growing parts of the world newlineand has been reported to cause losses of upto 50% in the field. The pathogen newlineenters rice leaves through either wounds or natural openings called hydathodes newline(water pores) that are concentrated at the leaf edges. The bacterium multiplies in newlinethe xylem vessels and migrates through the leaf. The symptoms are characterized newlineby drying of the leaf from the tip downwards. newlineAlthough the pathology of the bacterial blight pathogen has been studied in newlinedetail by several workers over the last 50 years, very little information is available newlineabout the genetics of the pathogen, especially of the genes involved in newlinepathogenesis. A number of virulence genes have been cloned from other plant newlinepathogenic bacteria such as Erwinia, Pseudomonas and other species of the genus newlineXanthomonas (Xanthomonas campestris pv. campestris, X. c. pv. glycines, X newlinecitri, etc. ) but genetic studies of X. oryzae pv. oryzae have lagged behind in newlinecomparison. Part of the reason for this has been the lack of adequate genetic tools newlineto study this bacterium. As a result, very few virulence genes have been identified newlineand the molecular basis of pathogenesis for this bacterium remains largely newlineunknown. newlineA major drawback for conducting genetic studies of X. oryzae pv. oryzae has newlinebeen the lack of a system for performing transposon mutagenesis. In recent years, newlinethe application of transposon technology has· revolutionized studies on bacterial newlinegenetics. The objective of this thesis is to develop transposon mutagenesis newlineprotocols for X. oryzae pv. oryzae and to use transposon-induced mutants to newlineenhance our understanding of rice-Xanthomonas interaction. The bacterial newlineTransposonS (TnS) has been chosen for this study because it has been shown to newlinetranspose in a number of different bacterial species.