Several genes involved in copper trafficking have been iden- tified in Arabidopsis. We have previously shown that one of these, CCH, is expressed at basal levels throughout the plant and is induced in leaves undergoing senescence (Himelblau et al. 1998). The yeast homolog of CCH, ANTIOXIDANT1, is known to interact with Ca2 -SENSITIVE CROSS-COMPLE- MENTER2 (CCC2), a copper-transporting ATPase in the post- Golgi membrane (Pufahl et al. 1997). We identified a putative homolog of CCC2 from Arabidopsis and initiated a study of the possible role of the homolog in leaf senescence. While this work was in progress, two groups reported that this gene, now called RESPONSIVE-TO-ANTAGONIST1 (RAN1), is a functional homolog of CCC2 (Hirayama et al. 1999, Woeste and Kieber 2000). It is possible that