CONICET | Buscador de Institutos y Recursos Humanos

Plant senescence involves several events that occur at the finalstages of development, or are initiated in response to stress. The lossof green colour caused by chlorophyll degradation is the mostcharacteristic symptom. Broccoli (Brassica oleracea) belongs to thefamily of Cruciferae. It is harvested when inflorescences areimmature, which causes considerable stress and triggers thesenescence. In this work, we studied by RT-PCR the effect of 1-MCP, an ethylene inhibitor agent, on the expression of genesassociated to chlorophyll degradation pathway: Chlorophyllase 1(BoCHL1), Chlorophyllase 2 (BoCHL2), Pheophytinase (BoPPH)and Pheophorbide a oxigenase (BoPaO). Broccoli heads weretreated with 1-MCP and stored in dark at 22ºC for five days. Therelative expression of BoCLH1 decreased continuously duringsenescence in both control and treated samples. In the case ofBoCLH2, the expression increased after 72 h and then diminishedafter 120 h in controls, whereas in 1-MCP treated samples theexpression was higher than in controls at 72 h without decreasingafterwards. The relative expression of BoPPH increased after 72 hand then diminished in controls. The treatment with 1-MCP inducedthe peak of BoPPH expression after 120 h. The expression of BoPaOwas similar to that of BoPPH and BoCHL2 in controls. Thetreatment did not modify this pattern but the relative expression waslower.