Isolation and Expression Analysis of the Ethylene Receptor Gene MiETR1b in Mango (Mangifera indica)

A mango ETHYLENE RESPONSE1 (ETR1) gene, designated MiETR1b, was isolated from the cotyledon of mango (Mangifera indica L. ‘Zihua’) using RT-PCR, and the 5′ and 3′ rapid amplification of cDNA ends. The full-length cDNA was 2 530 bp, with an open reading frame of 2 220 bp, and it encoded a putative protein of 739 amino acids. The genomic DNA sequence of MiETR1b was 4 116 bp in length, having a 3 305 bp sequence from the start to terminator codon, containing six exons and five introns. The deduced amino acids possessed conserved domains of the GAF and HATPase_c superfamilies. A phylogenetic tree analysis indicated that MiETR1b had the highest similarity to MiETR1 from M. indica and a high similarity to CsERS1, DlETR1, TcERS1 and PtETR1. Quantitative real-time PCR showed that MiETR1b was expressed in the proximal and distal cut surfaces throughout the adventitious root formation period. Meanwhile, the expression of MiETR1b in the distal cut surface was significantly up-regulated within 6–48 h. Pre-treatments with indole-3-butyric acid and 2,3,5-triiodobenzoic acid significantly down-regulated MiETR1b expression at 1 d and 6 h, respectively. However, more ethylene was produced from 12 to 24 h, while ethylene production decreased after 4 days of culturing. In conclusion, MiETR1b might play an important role during the adventitious root formation of mango cotyledon segments, which is related to ethylene production.