S23 - Session O6 - Manipulating tomato climacteric ripening by mutating or over expressing ICDH1 a feasible mediator between respiration and ethylene production

Authors: Dan Gamrasni *, Amit Asiag-Tabatznik, Tomer Lindman, Tom Shlomovich, Amir Raz , Martin Goldway

Fruits have two basic forms of ripening: climacteric and non-climacteric. Climacteric ripening is characterized by a climax of respiration along with an increase in ethylene production, whereas non-climacteric fruits present a low respiration rate and minor or no ethylene production. The relationship between these two central processes of climacteric ripening is well documented but not fully understood. Previously, following exposure of tomato fruit to the ethylene inhibitor 1-methylcyclopropene (1-MCP) at three pre-climacteric stages (immature green, mature green and breaker), we showed that the isocitrate dehydrogenase1 (SlICDH1) gene was down-regulated at all of the stages examined, suggesting that ethylene is involved in its regulation. To elucidate the role of SlICDH1 in climacteric ripening we mutated SlICDH1 in Micro-Tom tomatoesusing CRISPR/Cas9 that led to a deletion of about half of the protein. In addition, we generated Micro-Tom plants that overexpressed (OE) the SlICDH1 gene using the CaMV35S promoter. The respiration and ethylene production rates of slicdh1 fruit was lower with delayed ripening and prolonged shelf life while no physiological alterations in the plant phenology were observed. In contrast, the OE- SlICDH1 fruit exhibited an earlier peak of ethylene production but there was no significant effect on the fruit respiration rate. In addition, the plant had shorter internodes. Sequence analysis of the promotor region of SlICDH1 identified a few motifs recognized by ethylene induced transcription factors. These findings suggest that SlICDH1 is involved in the molecular association between ethylene and respiration during the climacteric phase of fruit ripening. From the agricultural perspective, a mutation in the cytosolic Sl-ICDH1 can increase the shelf-life of the fruit and reduce postharvest losses while overexpression of the gene can be useful tool for enhancing ripening when necessary.