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Our lab has shown that mutations at the Arabidopsis locus REVERSION-TO-ETHYLENE-SENSITIVITY1 (RTE1) result in the loss of ETR1 ethylene receptor function. This is based on the ability of rte1 mutations to suppress ethylene insensitive mutations in the ethylene receptor gene etr1, as well as the fact that rte1 mutants have the same enhanced ethylene response phenotype as the etr1 null mutant. RTE1 encodes a novel integral membrane protein with homologues in other plants and animals, including one copy in humans. We are interested in uncovering the unknown molecular function of RTE1 and its homolog in Arabidopsis named RTE-HOMOLOG (RTH). One approach we are taking is to analyze the basis of rte1 suppression of etr1-2 at the protein level. Immunoblot and immunofluorescence assays indicate no obvious changes in the level of ETR1 protein and show correct localization of the ETR1 protein in the rte1 null background. Preliminary results also indicate correct dimer formation of ETR1 in the rte1 null background. To identify the role of RTH, we are currently analyzing the rth null mutant for any involvement iit may have in the ethylene-signaling pathway. The rth null mutant does not show the same phenotypes as the rte1 null mutant, and the rte1 rth double null mutant does not display any additive effects, suggesting that the two loci are not redundant. Interestingly, the rth single null mutant appears to have an opposite phenotype (lengthening of the hypocotyl in dark-grown seedlings) from the rte1 null mutant. Consistent with this finding, over-expression of the wild-type RTH gene confers a shorter hypocotyl than the wild type. Further experiments to understand the basis for this phenotype and its possible relation to ethylene are in progress.
“FUTBOL” Team at the University of Buenos Aires
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