The isocitrate dehydrogenase 1 gene is associated with the climacteric response in tomato fruit ripening

Climacteric ripening is related to a respiratory climax accompanied by an exponential increase in ethylene production. This association is not fully understood. Tomato fruit were exposed to the ethylene antagonist 1-methylcyclopropene (1-MCP) at different ripening stages and their transcriptome was monitored. ISOCITRATE DEHYDROGENASE 1 (ICDH, Solyc01g005560.2.1) was the only respiratory process related gene that was down regulated at all ripening stages including the mature green. Silencing SlICDH1using VIGS (virus indused gene silencing), to about 50 % of its native expression, in Micro-Tom tomatoes, reduced both respiration and ethylene production of the harvested fruit. Silenced SlICDH1 tomatoes also exhibited prolonged ripening and reduced susceptibility to the pathogen Botrytis cinerea. In addition, ethylene response factors binding sites were identified in the promotor and in the first intron of SlICDH1. These results suggest that regulation of SlICDH1 is a key step in the initiation of the climacteric rise of respiration via ethylene regulation.