A Strong Loss-of-Function Mutation in RAN1 Results in Constitutive Activation of the Ethylene Response Pathway as Well as a Rosette-Lethal Phenotype

Abstract

A recessive mutation was identified that constitutively activated the ethylene response pathway in Arabidopsis and resulted in a rosette-lethal phenotype. Positional cloning of the gene corresponding to this mutation revealed that it was allelic to responsive to antagonist1 (ran1), a mutation that causes seedlings to respond in a positive manner to what is normally a competitive inhibitor of ethylene binding. In contrast to the previously identified ran1-1 and ran1-2 alleles that are morphologically indistinguishable from wild-type plants, this ran1-3 allele results in a rosette-lethal phenotype. The predicted protein encoded by the RAN1 gene is similar to the Wilson and Menkes disease proteins and yeast Ccc2 protein, which are integral membrane cation-transporting P-type ATPases involved in copper trafficking. Genetic epistasis analysis indicated that RAN1 acts upstream of mutations in the ethylene receptor gene family. However, the rosette-lethal phenotype of ran1-3 was not suppressed by ethylene-insensitive mutants, suggesting that this mutation also affects a non-ethylene-dependent pathway regulating cell expansion. The phenotype of ran1-3 mutants is similar to loss-of-function ethylene receptor mutants, suggesting that RAN1 may be required to form functional ethylene receptors. Furthermore, these results suggest that copper is required not only for ethylene binding but also for the signaling function of the ethylene receptors.

REVERSION-TO-ETHYLENE SENSITIVITY1 , a conserved gene that regulates ethylene receptor function in Arabidopsis

“…Defects in RAN1 are thought to severely disrupt the formation of functional wild-type ethylene receptors, presumably because of improper copper loading. Similar to rte1, mutations in ran1 are suppressed by etr1-1 (39,40). In the case of ran1, this implies that the etr1-1 receptor is stable in the absence of copper and locked into the repressive signaling state, unlike wild-type ethylene receptors.…”

“…One other protein known to affect ethylene receptor function is RAN1, a homolog of the human Menkes͞Wilson P-type ATPase copper transporters (39,40). Defects in RAN1 are thought to severely disrupt the formation of functional wild-type ethylene receptors, presumably because of improper copper loading.…”

The effects of Group 11 transition metals, including gold, on ethylene binding to the ETR1 receptor and growth of Arabidopsis thaliana

“…Additionally, genetic studies indicate that the RAN1 copper transporter acts upstream of the receptors [9,10]. Together, these studies support a model where copper ions are delivered to and required by the ethylene receptors.…”

Transcription Analysis of Arabidopsis Membrane Transporters and Hormone Pathways during Developmental and Induced Leaf Senescence

“…The five ET receptors or the next downstream protein, AtCTR1, are not regulated in NS, DIS, or DET, but several other components of ET signal transduction are. The TP-like AtRAN1 protein, which might be required to form functional ET receptors (Woeste and Kieber, 2000), and the downstream component AtEIN3 are significantly up-regulated in all three senescence experiments, most rapidly in DIS and DET (Supplemental Fig. 6, H and I).…”