The effect of 1-methylcyclopropene (1-MCP) on expression of ethylene receptor genes in durian pulp during ripening.

Rapid fruit ripening is a significant problem that limits the shelf life of durian, with ethylene having a major impact on the regulation of this event. Durian treated with ethephon ripened 3 d after treatment with increased pulp total soluble solids, ethylene production of the whole fruit and decreased pulp firmness compared to the control fruit. 1-MCP treatment delayed ripening by up to 9 d with inhibited accumulation of total soluble solids, color change, softening and ethylene production. Genes related to ethylene perception (DzETR1 and DzETR2) and the signaling pathway (DzCTR1, DzEIL1 and DzEIL2) in the pulp were investigated during this process, using qPCR to quantify changes in gene transcription. All candidate genes were significantly up-regulated in ripening durian pulp. Ethephon treatment increased the expression of DzETR1 and DzETR2 genes, while expression of DzCTR1, DzEIL1 and DzEIL2 were slightly affected. 1-MCP treatment significantly inhibited the expression of the DzETR2 and DzEIL1 genes. The promoters of DzETR2 genes were isolated and their activation by fruit transcription factors studied using transient expression in tobacco leaves. It was found that members of the kiwifruit and apple EIL1, EIL2 and EIL3 genes strongly activated the DzETR2 promoter. These results suggest that ethylene-induced ripening of durian is via the regulation of DzETR2 by EIL transcription factors.

Ethylene and pollination decrease transcript abundance of an ethylene receptor gene in Dendrobium petals.

We studied the expression of a gene encoding an ethylene receptor, called Ethylene Response Sensor 1 (Den-ERS1), in the petals of Dendrobium orchid flowers. Transcripts accumulated during the young floral bud stage and declined by the time the flowers had been open for several days. Pollination or exposure to exogenous ethylene resulted in earlier flower senescence, an increase in ethylene production and a lower Den-ERS1 transcript abundance. Treatment with 1-methylcyclopropene (1-MCP), an inhibitor of the ethylene receptor, decreased ethylene production and resulted in high transcript abundance. The literature indicates two kinds of ethylene receptor genes with regard to the effects of ethylene. One group shows ethylene-induced down-regulated transcription, while the other has ethylene-induced up-regulation. The present gene is an example of the first group. The 5' flanking region showed binding sites for Myb and myb-like, homeodomain, MADS domain, NAC, TCP, bHLH and EIN3-like transcription factors. The binding site for the EIN3-like factor might explain the ethylene effect on transcription. A few other transcription factors (RAV1 and NAC) seem also related to ethylene effects.