Deregulated Copper Transport Affects Arabidopsis Development Especially in the Absence of Environmental Cycles    

Abstract

Copper is an essential cofactor for key processes in plants, but it exerts harmful effects when in excess. Previous work has shown that the Arabidopsis (Arabidopsis thaliana) COPT1 high-affinity copper transport protein participates in copper uptake through plant root tips. Here, we show that COPT1 protein localizes to the plasma membrane of Arabidopsis cells and the phenotypic effects of transgenic plants overexpressing either COPT1 or COPT3, the latter being another high-affinity copper transport protein family member. Both transgenic lines exhibit increased endogenous copper levels and are sensitive to the copper in the growth medium. Additional phenotypes include decreased hypocotyl growth in red light and differentially affected flowering times depending on the photoperiod. Furthermore, in the absence of environmental cycles, such as light and temperature, the survival of plants overexpressing COPT1 or COPT3 is compromised. Consistent with altered circadian rhythms, the expression of the nuclear circadian clock genes CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) is substantially reduced in either COPT1-or COPT3-overexpressing plants. Copper affects the amplitude and the phase, but not the period, of the CCA1 and LHY oscillations in wild-type plants. Copper also drives a reduction in the expression of circadian clock output genes. These results reveal that the spatiotemporal control of copper transport is a key aspect of metal homeostasis that is required for Arabidopsis fitness, especially in the absence of environmental cues.

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

“…The COPT-family transporters are also responsible for Cu uptake in leaves and other shoot organs. In addition to their expression in root, AtCOPT1 and OsCOPT1 also showed high expression in the plasma membrane of leaves supporting the idea of a role in the Cu transport in shoot (Andres-Colas et al, 2010;Yuan et al, 2011). OsCOPT2 and OsCOPT3 had relatively high expression levels in leaf and panicle .…”

“…AtCOPT1, the first COPT family member identified and characterized, is expressed in the plasma membrane of roots and has an important role in the acquisition of Cu monovalent ions. AtCOPT2 and AtCOPT3 are also present in the plasma membrane of root tissues and seem to play a role in Cu acquisition from the rhizosphere (Andres- Colas et al, 2010). Furthermore, it is hypothesized that members of the Zinc-Regulated Transporter and Iron-Regulated Transporter (ZRT-IRT)-like proteins (ZIP) family can mediate the uptake and transport of Cu in both Arabidopsis thaliana and Medicago truncatula (del Pozo et al, 2010;Stephens et al, 2011).…”

Reciprocal Interaction of the Circadian Clock with the Iron Homeostasis Network in Arabidopsis

“…It is becoming increasingly clear that in plants, clock function not only regulates many aspects of cellular metabolism and physiology (Harmer, 2009;McClung and Gutiérrez, 2010;Pruneda-Paz and Kay, 2010;McClung, 2011), including solute transport , but is, in turn, modulated by the cellular metabolic state. Plant clock function has been shown to respond to the uptake and homeostasis of Suc (Bläsing et al, 2005;Knight et al, 2008;Dalchau et al, 2011) and other nutrients, including magnesium (Mg; Hermans et al, 2010), copper (Cu; Andrés-Colás et al, 2010;Peñarrubia et al, 2010), and nitrogen (N; Gutiérrez et al, 2008). Similarly, clock function is highly responsive to metabolic state, including redox status, in cyanobacteria (Ivleva et al, 2005;Rust et al, 2011) and 1 This work was supported by the National Science Foundation (grant nos.…”

Daily rhythmicity of high affinity copper transport

“…In this sense, Cu sufficiency inhibiting SPL7 function 8 forms a negative autoregulatory feedback loop that has been proposed to produce an oscillation in COPT2 expression, and subsequently, in intracellular Cu levels with an approximate circadian period. 20 Cu content has been shown to affect the expression of some central components of the circadian clock, 15,21 such as the single Myb domain transcription factors CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) and LATE ELONGATED HYPO-COTYL (LHY) (for review, 2 ) and the protein GIGANTEA (GI), known to modulate other circadian clock components (for review, 22 ). LHY and GI include, respectively, 3 and 2 GTAC boxes in their promoter regions, respectively, which suggests a direct involvement of SPL7 in their increased abundance under Cu deficiency (Fig.…”

“…15,21 Light signaling and Cu homeostasis pathways are coordinated through the interaction of the transcription factors SPL7 15 and ELON-GATED HYPOCOTYL5 (HY5). 23 This mutual dependence of Cu transport, circadian clock, and light signaling pathways would lead to the synchronization of inextricably linked outputs from these intertwined and cyclic processes.…”