Ethylene and developmental signals regulate expression of lipoxygenase genes during tomato fruit ripening

The role of ethylene in regulating the expression of three lipoxygenase (LOX) genes TomloxA, TomloxB and TomloxC during fruit ripening has been investigated. The study used a combination of low-ethylene fruit containing an ACC oxidase (ACO1) sense-suppressing transgene and tomato fruit ripening mutants deficient in ethylene perception in the case of Never-ripe (Nr) or ripening in the case of the ripening-inhibitor (rin). The results indicate that the three genes are differentially regulated during fruit ripening and that a combination of ethylene and developmental factors influence their expression. The expression of TomloxA declines during ripening and this is delayed in the ACO1 transgenic low-ethylene and Nr fruit indicating that this phenomenon is ethylene regulated. However, transcript abundance also declines during rin fruit development indicating that developmental factors also influence the expression of TomloxA. TomloxB expression increases during fruit ripening and expression is increased by ethylene as reduced accumulation is evident in transgenic and mutant fruit. The same ethylene up-regulated and ripening-related expression is shown by TomloxC, however, expression increases in rin fruit at the onset of colour change, indicating that there may also be a developmental component regulating TomloxC expression. These results indicate that individual LOX isoforms are differentially regulated and may have distinct functions during tomato fruit ripening.