MOLECULAR-CLONING OF A RIPENING-SPECIFIC LIPOXYGENASE AND ITS EXPRESSION DURING WILD-TYPE AND MUTANT TOMATO FRUIT-DEVELOPMENT

A 94-kD protein that accumulates predominately in tomato (Lycopersicon esculentum) fruit during ripening was purified, and antibodies specif ic for the purified protein were used to isolate cDNA clones from a re d-ripe fruit cDNA library. A sequence analysis of these cDNAs and cros s-reactivity of the 94-kD-specific antibodies to the soybean lipoxygen ase (LOX) L-1, L-2, and L-3 proteins and soybean LOX L-1-specific anti bodies to the 94-kD protein identified it as a member of the LOX gene family. Maximum levels of the 94-kD LOX mRNA and protein are present i n breaker to ripe and red-ripe stages, respectively. Expression of 94- kD LOX in different tissues from mature green and red-ripe tomato frui ts was found to be greatest in the radial walls of ripe fruit, but imm unocytolocalization using tissue printing suggests that the highest ac cumulation of its protein occurs in locular jelly. None of 94-kD LOX i s expressed in nonripening mutant fruits of any age. Never-ripe mutant fruit accumulate the 94-kD LOX mRNA to levels similar to those obtain ed in wild-type fruit, but fail to accumulate the 94-kD LOX protein. C ollectively, the results show that expression of 94-kD LOX is regulate d by the ripening process, and ethylene may play a role in its protein accumulation.