Sequence Analysis of Ethylene Response Sensor Gene Isolated from Vanda Miss Joaquim Flower

Abstract

A specific ethylene receptor protein is a major key for ethylene perception into plant tissues. Thus, the Ethylene Response Sensor (ERS) gene was isolated from the ethylene-sensitive flowers of Vanda Miss Joaquim and its deduced ethylene response sensor (ERS) was aligned with three other reported orchid ERS genes to identify the specific divergence in orchid ethylene receptor proteins. The results from multiple alignment showed that the amino acid sequence of the Vanda ERS was 95% identical to Phalaenopsis ERS (the ethylene-sensitive species), but shared 90–91% identity with the ERS isolated from two ethylene-insensitive orchid species, Dendrobium hybrid Khao Sanan and Oncidium Gower Ramsey. The most conserved regions were located at the N-terminus of the polypeptide being three transmembrane hydrophobic regions; however, the most variable regions, particularly for the Dendrobium ERS and Oncidium ERS, were located in the ATP-binding site of the histidine kinase domain and the amino acid sequence of the downstream histidine kinase domain at the C-terminus. The findings suggest the sequence similarity in the ATP-binding site can be used to distinguish the closely related ERS proteins. In considering the level of ERS gene expression, there was an abundance of ERS transcript accumulation in fully opened Vanda Miss Joaquim flowers (particularly in the column and the lip followed by the perianth tissue) compared with root and leaf tissues.