Effects of exogenous auxin on pigments and primary metabolite profile of postharvest tomato fruit during ripening

- Auxin impact pigments and primary metabolites accumulation of tomato during ripening.
- Metabolites changes induced by auxin are partly restored at the end of ripening.
- Exogenous auxin application may enhance fruit acidity.

Auxin is an important plant hormone and plays crucial roles in regulating fruit ripening. The delay of ripening after auxin treatment has been found in tomato and other fleshy fruit. However, the influence of auxin on metabolites alteration during tomato ripening period has not been extensively studied. To investigate the impact of exogenous auxin on tomato fruit quality, pigment metabolism, primary metabolite profiling, and the expression of selected ripening-related transcription factor genes were analyzed. The results showed that exogenous auxin significantly interfered the accumulation and conversion of pigments, total phenolics and flavonoids but did not largely influence the final content of these compounds in full ripe tomato fruit. Dramatic changes on the content of primary metabolites were induced by auxin during tomato ripening period and the alterations were not able to be completely restored at the end of ripening. The contents of citric acid, threonic acid and succinic acid were increased whereas alanine and aspartic acid accumulation was repressed in auxin-treated fruit. The expression patterns of transcription factor genes related to ripening were also disturbed by exogenous auxin. The present study provided an overall insight on how auxin regulates pigment and primary metabolite accumulation during ripening stage and offered useful information for further investigation of auxin impact on fruit quality.