Positive feedback regulation may occur during tomato ripening: expression of PDS and ZDS increases in response to low quantities of end-products of the carotenoid pathway, such as β-carotene, xanthophylls or ABA [ 49, 50].
This is consistent with early ripening expression of amino acid decarboxylases leading to amine synthesis in a number of fruits [ 44, 45].
However, as the berries ripened, expression of each of these genes was reduced.
At the onset of ripening, expression patterns of numerous genes involved in these ripening-associated phenomena are upregulated in a highly synchronized fashion, indicating that ripening is controlled by a highly systematic and sophisticated transcriptional mechanism.
Late in ripening, F3'5'H expression was predominated by transcripts of F3'5'Hf, -g,-h, and -l.
In this example, comparing graph heights between stages highlights ripening related expression of gene CUFF.187, which is homologous to genes in many other plant species but has no known function.
To further investigate the implications of ethylene and auxin in grape berry ripening, the expression of TAR1-4, YUC3, YUC3 as well as ACS1 and ACO1 was analysed in Shiraz berries from 3 weeks post flowering (wpf) through to harvest at 16 wpf.
During fruit ripening, the expression of vacuolar H+-ATPase A subunit was increased in tomato [ 48] and grape [ 49], while a number of other subunits are still largely uncharacterized at the molecular level.
To identify other genes that were potentially involved in ripening, the expression levels of genes from the two lines were compared.
Similarly, the miraculin-like gene can be distinguished from the others because throughout ripening the expression profile of this gene is completely the opposite between Chardonnay and Cabernet Sauvignon berries (data not shown).
This was further corroborated by our findings in that ethylene treatment did not induce any significant changes towards ripening, and the expression of all four measured ETR isoforms at the B stage in capsicum after ethylene exposure were also constant compared to the control.
