In order to understand the role of candidate genes related to fruit ripening, we have used the latest technology in gene editing: ¨CRISPR/Cas9¨.
We used the ´knockout gene strategy´ in melon, which in addition of being an important economic crop, became a good model to study this trait since it contains genotypes from both major groups of ripening behavior. These groups are climacteric fruits, in which ripening is characterized by a burst of ethylene; and non-climacteric fruits, in which ethylene production does not increase during the ripening process.
Ethylene is a plant hormone which regulates many processes of the plant, being one of them fruit ripening. In climacteric fruits, the increase of ethylene triggers plant metabolism adaptations that lead to changes in fruit colour, flavour and texture.
In the MeloCRISP project, we studied two ripening candidate genes in a climacteric genetic background (cantalupensis melon type ´Vedrantais´). The knockout of these genes by CRISPR /Cas9 resulted in several edited plants for each of the two genes. The selected edited plants were pollinated to produce seeds and the second generation of the edited plants was grown under glasshouse conditions for evaluation of their ripening behavior in comparison with non-edited climacteric plants. To better understand the role of these genes, we daily monitored the plants by measuring the ethylene production in attached fruits (as an indicator of climacteric ripening process) as well as several ripening associated traits such as aroma production, external color change, abscission layer formation in the pedicel of the fruit, the firmness, and the harvest time (date when the fruit abscised from the plant).
The edited plants showed an earlier ripening profile and a different profile of fruit ripening and ethylene production compared to climacteric not edited plants. For one of the target genes, ethylene production was higher compared to the control plants whereas for the other gene no changes were observed on the quantity of the hormone. However, for both edited plants, ethylene production started earlier than in the control plants revealing the role of these genes in the regulation of the ethylene production. The final results showed that both genes have a role in the ripening process affecting the initiation of the ripening process but without affecting other important traits such as firmness.
A scientific article with these results is currently being drafted and it is expected to be published in an open access peer-reviewed journal. The project background, concept and some preliminary results have also been communicated to non-specialized audience, including workshops for high-school students.
