Effect of 1-MCP on the expression of chlorophyll degrading genes during senescence of broccoli (Brassica oleracea L.)

Abstract

Degreening caused by chlorophyll degradation is the most evident visual manifestation of broccoli senescence and deterioration. In this work, the effect of 1-MCP on color change, chlorophyll degradation and expression of genes associated to chlorophyll catabolism was evaluated during postharvest storage. 1-MCP treatment markedly delayed degreening and reduction of chlorophyll content. The expression of genes encoding chlorophyllases showed different behaviors. In controls, the expression of BoCLH1 decreased during postharvest storage while that of BoCLH2 increased after 72 h and then decreased. The treatment with 1-MCP did not cause any effect on BoCLH1 but induced a higher expression of BoCLH2. A high BoPPH expression level was found in senescent broccoli florets, but the up-regulation of this gene was delayed by 1-MCP treatment. The expression of BoPaO, a gene encoding a pheophorbide a oxygenase, increased after three days and then decreased. In contrast, this expression was reduced in treated broccoli. Finally, the expression of BoRCCR decreased during senescence and the treatment with 1-MCP caused a higher decrement. These results show that postharvest 1-MCP inhibit selectively some of the genes encoding enzymes related chlorophyll catabolism.