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

The role of ethylene in regulating the expression of three lipoxygenase (LO X) genes TomloxA, TomloxB and TomloxC during fruit ripening has been invest igated. The study used a combination of low-ethylene fruit containing an AC C oxidase (ACO1) sense-suppressing transgene and tomato fruit ripening muta nts deficient in ethylene perception in the case of Never-ripe (Nr) or ripe ning in the case of the ripening-inhibitor (rin). The results indicate that the three genes are differentially regulated during fruit ripening and tha t a combination of ethylene and developmental factors influence their expre ssion. The expression of TomloxA declines during ripening and this is delay ed in the ACO1 transgenic low-ethylene and Nr fruit indicating that this ph enomenon is ethylene regulated. However, transcript abundance also declines during rin fruit development indicating that developmental factors also in fluence the expression of TomloxA. TomloxB expression increases during frui t ripening and expression is increased by ethylene as reduced accumulation is evident in transgenic and mutant fruit. The same ethylene up-regulated a nd ripening-related expression is shown by TomloxC, however, expression inc reases in rin fruit at the onset of colour change, indicating that there ma y also be a developmental component regulating TomloxC expression. These re sults indicate that individual LOX isoforms are differentially regulated an d may have distinct functions during tomato fruit ripening.