Isolation and molecular characterization of the ethylene receptor ETRI from 'carabao' mango (Mangifera indica L.) fruit

Signal transduction of ripening in climacteric mango is controlled by an ethylene-specific receptor protein in the plasma membrane of plant cells. To regulate ripening in mango by manipulating ethylene sensitivity, the gene encoding the receptor protein was isolated and characterized. Partial cDNAs corresponding to ETRI homologous have been cloned and characterized from ripening mesocarp tissues derived from mango cv. carabao using reverse transcription followed by polymerase chain reaction (RT-PCR). The primers ATGGCC (A/T) GCTGATG (forward) and ATAAAACGCTCCTC (reverse) were designed based on multiple sequence alignment analyses of ETRI genes available at the GenBank database. Total RNA isolate from ripening mesocarp tissues of mango was used as template for RT-PCR and generated at least two types of ETRI homologous- 1.1 and 1.7 kb PCR fragments. These two ETRI homologues were claimed in TOPO-TA vectors for DNA sequencing. Genomic DNA isolate d from newly emerging leaf tissues was also used as template for PCR and generated multiple PCR bands suggesting that ethylene receptors belong to a multigene family. Sequence analyzes of the partial cDNAs (Fragment A1, A2,B to F) revealed that the ethylene receptor in mango belongs to the ETRI-like subfamily (Type 1) with 3 hydrophobic domains at the sensor-region of the receptor. Four out of seven fragments were located at the N-terminal sensor domains while the remaining three fragments were located either at the kinase and receiver domains. The partial ripening-related cDNA sequences of ETRI homologues from mango cv. Carabao could be used for manipulating ethylene sensitivity or perception by antisense or co-suppressions technology and interference RNA (iRNA). This study represented the first DNA sequence for an ethylene-specific receptor protein involved in the ripening of the climacteric fruit-mango, cv. Carabao.