Two xylanase genes of the vascular wilt pathogen Fusarium oxysporum are differentially expressed during infection of tomato plants

Two genes encoding putative family F xylanases from the tomato vascular wil t pathogen Fusarium oxysporum f.sp. lycopersici have been cloned and sequen ced. The two genes, designated xyl2 and xyl3, encode proteins with calculat ed molecular masses of 33 and 39.3 kDa and isoelectric points of 8.9 and 6. 7, respectively. The predicted amino acid sequences show significant homolo gy to other family F xylanases. XYL3 contains a cellulose-binding domain in its N-terminal region. Southern analysis suggested that xyl2 and xyl3 homo logs are also present in other formae speciales of F. oxysporum. Both genes were expressed during growth on oat spelt xylan and tomato vascular tissue in vitro. RT-PCR revealed that xyl3 is expressed in roots and in the lower stems of tomato plants infected by F. oxysporum f.sp. lycopersici througho ut the whole disease cycle, whereas xyl2 is only expressed during the final stages of disease.