The Copper Transporter RAN1 Is Essential for Biogenesis of Ethylene Receptors in Arabidopsis

Abstract

Plants utilize ethylene as a hormone to regulate multiple developmental processes and to coordinate responses to biotic and abiotic stress. In Arabidopsis thaliana, a small family of five receptor proteins typified by ETR1 mediates ethylene perception. Our previous work suggested that copper ions likely play a role in ethylene binding. An independent study indicated that the ran1 mutants, which display ethylene-like responses to the ethylene antagonist trans-cyclooctene, have mutations in the RAN1 copper-transporting P-type ATPase, once again linking copper ions to the ethylene-response pathway. The results presented herein indicate that genetically engineered Saccharomyces cerevisiae expressing ETR1 but lacking the RAN1 homolog Ccc2p (⌬ccc2) lacks ethylene-binding activity. Ethylene-binding activity was restored when copper ions were added to the ⌬ccc2 mutants, showing that it is the delivery of copper that is important. Additionally, transformation of the ⌬ccc2 mutant yeast with RAN1 rescued ethylene-binding activity. Analysis of plants carrying loss-of-function mutations in ran1 showed that they lacked ethylene-binding activity, whereas seedlings carrying weak alleles of ran1 had normal ethylene-binding activity but were hypersensitive to copper-chelating agents. Altogether, the results show an essential role for RAN1 in the biogenesis of the ethylene receptors and copper homeostasis in Arabidopsis seedlings. Furthermore, the results indicate cross-talk between the ethylene-response pathway and copper homeostasis in Arabidopsis seedling development.

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…AtHMA1 and HvHMA1, present in the chloroplast envelope, are broad-specificity exporters of metals from chloroplasts and may play a specialized role in Cu mobilization (Mikkelsen et al, 2012). AtHMA7 (RAN1), the first functionally characterized heavy metal ATPase, is responsible for the biogenesis of ethylene receptors by supplying Cu at the endoplasmic reticulum and also for Cu homeostasis in seedling development (Binder et al, 2010). The rice mitochondrial Fe transporter (MIT) also appears to regulate the influx of Cu, although more studies are needed to confirm this (Bashir et al, 2011).…”

Overexpression of ARGOS Genes Modifies Plant Sensitivity to Ethylene, Leading to Improved Drought Tolerance in Both Arabidopsis and Maize

“…) and the latter, a transporter, providing the ethylene cofactor copper and also playing a role in the biogenesis of active ethylene receptors (Hirayama et al, 1999;Binder et al, 2010). Many aspects of the ethylene signaling pathway and the sequences of the proteins involved are conserved between dicots and monocots (Guillaume and Sauter, 2008).…”

“…EIN2, an ER-tethered protein, functions as a shuttle to transduce the signal from the membrane to the nucleus via its cleavable C-terminal domain (Ju et al, 2012;Qiao et al, 2012). Proteins that modulate ethylene perception include REVERSION-TO-ETHYLENE SENSITIVITY1 (RTE1) and RESPONSIVE-TO-ANTAGONIST1, the former promoting the activity of ETR1 (Resnick et al, 2006Dong et al, 2010) and the latter, a transporter, providing the ethylene cofactor copper and also playing a role in the biogenesis of active ethylene receptors (Hirayama et al, 1999;Binder et al, 2010). Many aspects of the ethylene signaling pathway and the sequences of the proteins involved are conserved between dicots and monocots (Guillaume and Sauter, 2008).…”

A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

“…AtHMA6 (PAA1, for P-type ATPase of Arabidopsis1) localized at the chloroplast periphery has been proposed to transport Cu over the chloroplast envelope, whereas AtHMA8 (PAA2) localized at the thylakoid membranes most likely transports Cu into the thylakoid lumen to supply plastocyanin (Shikanai et al, 2003;Abdel-Ghany et al, 2005). Finally, AtHMA7 (RESPONSIVE-TO-ANTAGONIST1) is responsible for delivering Cu to ethylene receptors and Cu homeostasis in the seedlings (Hirayama et al, 1999;Woeste and Kieber, 2000;Binder et al, 2010).…”