THE CLONING OF 2 TOMATO LIPOXYGENASE GENES AND THEIR DIFFERENTIAL EXPRESSION DURING FRUIT RIPENING

A membrane-associated lipoxygenase from breaker-stage fruit of tomato (Lycopersicon esculentum Mill.) was purified and partially sequenced. Using degenerate oligonucleotides corresponding to portions of this se quence, a cDNA was amplified by PCR and used to screen a breaker fruit cDNA library. Two clones, tomloxA and tomloxB, were isolated and one of these (tomloxA) corresponded to the isolated protein. Genomic clone s were isolated and sequence data from these were used to obtain the 5 ' ends of the cDNAs. The 2.8-kb cDNAs encode proteins that are similar in size and sequence to each other and to other plant lipoxygenases. DNA blot analysis indicated that tomato contains three or more genes t hat encode lipoxygenase. RNA blot analysis showed that tomloxA is expr essed in germinating seeds as well as in ripening fruit, where it reac hed its peak during breaker stage. tomloxB appears to be fruit specifi c and is at its highest level in ripe fruit.