(E)-2-hexenal regulates the chloroplast degradation in tomatoes

The concentrations of (E)-2-hexenal (E2H) have obvious correlation with the color change process in tomatoes during ripening. It is proposed that E2H may play a role in regulating the chloroplast degradation. In this study, the exogenous E2H was applied to tomato fruits and plants to create a higher concentration of E2H atmosphere than naturel released. A set of indices in response to E2H were detected. The color change was inhibited. The ethylene pathway and the involved genes were limited. The results of subcellular structure changes, the fatty acid profiles and the malondialdehyde (MDA) content supported that the chloroplast membranes were specifically degraded. The hydroperoxide lyase (HPL) and the lipoxygenase (LOX) pathway was activated to decompose the free fatty acids. In tomato plants at the harvest stage, E2H did not affect the ripe tomatoes, but inhibited the color changes of green tomatoes, accelerated the withering of the leaves and the branches, and made the fruits fall off easier. The chlorophagy was activated and the autophagosomes were observed to decompose the chloroplasts in leaves. In conclusion, E2H accelerated the chloroplast degradation, by which the color changes were regulated.