Analysis of the molecular basis ofPseudomonas syringaepv.tomatoresistance in tomato

摘要

Tomato (Lycopersicon esculentum) cultivars that contain thePtobacterial resistance locus also exhibit sensitivity to fenthion, an organophosphorous insecticide. Resistance toPseudomonas syringaepv.tomato (Pst)encoded by thePtogene and sensitivity to fenthion cosegregate in large F2populations and were apparently introgressed together into tomato from the wild speciesLycopersion pimpinellifolium. In order to isolate the genes responsible for these two phenotypes and to study their molecular basis, a multistep map-based cloning project was initiated. A closely linked RFLP marker was used to isolate a yeast artificial chromosome (YAC) clone that spanned thePtoregion. Transcribed sequences within thePtoregion were identified by isolating cDNA clones that hybridized to the YAC clone. Transformation of candidate cDNA clones into aPst-susceptible, fenthion-insensitive tomato line succeeded in identifying a cDNA conferringPstresistance and a separate cDNA conferring sensitivity to fenthion. The cDNA clones represent members of a tandemly repeated gene family and encode putative serine-threonine protein kinases. The role of these kinases in recognizing a signal fromPstor the fenthion molecule and in activating the plant response is currently being investigated.