Cloning and expression analysis of putative ethylene receptor genes BO-ETR1, BO-ETR2 and BO-ERS in harvested broccoli

摘要

Ethylene is involved in the premature senescence of broccoli after harvest. In an effort to understand the regulation of ethylene responses, we isolated three partial cDNAs from broccoli, BO-ETR1, BO-ERS, and BO-ETR2 as putative ethylene receptors, BO-ETR2 is a novel cDNA and it shared 77%, 68%, and 58% nucleotide identities with Arabidopsis ETR2 and tomato LeETR4, and BO-ETR1, respectively, in the corresponding regions of 479 bp long. Northern-blot analysis revealed that BO-ETR1 and BO-ERS mRNA were expressed in all examined parts of stem tissue and florets, but the transcription levels were higher in the stem tissue than in florets. During the broccoli senescence no significant change occurred in the expression of BO-ETR1 gene in either the stem or floret tissue. BO-ERS transcripts increased during the first 12 hr after harvest in the first layer of stem cutting, but decreased in the basal portion of curds. BO-ETR2 mRNA, which was maximum at harvest (0 hr), was detected only in the stem tissue. A significant reduction of BO-ETR2 transcripts was observed 36 hr after harvest. The results indicate that the gene expression for the above putative ethylene receptors in broccoli is regulated in a tissue specific manner.