Abstract:

The characteristic of ethylene production and gene expression of ethylene receptors were studied in pre-cooled broccoli which were stored under 20 ℃. The results showed that during 0-6 h of storage, the ethylene production increased in the cross section of stem (0-2 mm), while decreased markedly in florets. Changes in the activity of ACC synthase were in agreement with those of the ethylene production rate. ACC content increased from 0 h to 6 h and decreased from 6 h to 12 h in all tested tissues. The florets had the lowest level of ACC content. The MACC level in florets was relatively high and remained stable during the experimental period. The lowest level of MACC appeared in the basal portion of florets. Though it was significantly higher in florets than that in the stem tissues, the activity of ACC oxidase increased from 0 h to 12 h in all tested tissues，which was inconsistent with the ethylene production. Northern blot analysis showed that mRNA levels of BO-ACS1 and BO-ACO2 in stem tissues were higher than that in florets at 0 h; mRNA levels at 12 h were lower than that at 0 h. In florets, the mRNA level of BO-ACS1 didn't increase at 12 h, however mRNA level of BO-ACO2 increased significantly. The transcripts of BO-ETR1, BO-ERS, and BO-ETR2 in the first layer of the cross section of stem and the BO-ERS in the florets were higher at 12 h than that at 0 h. The mRNA of BO-ETR2 could be only detected in the stem tissues.

Key words: broccoli, ethylene, ethylene receptor, gene expression