The Arabidopsis Copper Transporter COPT1 Functions in Root Elongation and Pollen Development

Abstract

Copper plays a dual role in aerobic organisms, as both an essential and a potentially toxic element. To ensure copper availability while avoiding its toxic effects, organisms have developed complex homeostatic networks to control copper uptake, distribution, and utilization. In eukaryotes, including yeasts and mammals, high affinity copper uptake is mediated by the Ctr family of copper transporters. This work is the first report on the physiological function of copper transport in Arabidopsis thaliana. We have studied the expression pattern of COPT1 in transgenic plants expressing a reporter gene under the control of the COPT1 promoter. The reporter gene is highly expressed in embryos, trichomes, stomata, pollen, and root tips. The involvement of COPT1 in copper acquisition was investigated in CaMV35S::COPT1 antisense transgenic plants. Consistent with a decrease in COPT1 expression and the associated copper deprivation, these plants exhibit increased mRNA levels of genes that are down-regulated by copper, decreased rates of 64 Cu uptake by seedlings and reduced steady state levels of copper as measured by atomic absorption spectroscopy in mature leaves. Interestingly, COPT1 antisense plants also display dramatically increased root length, which is completely and specifically reversed by copper addition, and an increased sensitivity to growth inhibition by the copper-specific chelator bathocuproine disulfonic acid. Furthermore, COPT1 antisense plants exhibit pollen development defects that are specifically reversed by copper. Taken together, these studies reveal striking plant growth and development roles for copper acquisition by high affinity copper transporters.

Comparison of global responses to mild deficiency and excess copper levels in Arabidopsis seedlings

“…RNA was quantified by UV spectrophotometry and its integrity was visually assessed on ethidium bromidestained agarose gels. Total RNA (1.5 mg) was first converted into cDNA by reverse transcription using SuperScript II reverse transcriptase (Invitrogen) and anchored oligo(dT) 15 (Roche).…”

Examining the Specific Contributions of Individual Arabidopsis Metallothioneins to Copper Distribution and Metal Tolerance

“…When this capacity is surpassed, plants may down-regulate Cu transporters (e.g. AtCOP1; Sancenon et al, 2004) to limit further uptake of Cu or pump excess Cu into the rhizosphere. Excess Cu may also be transported to the shoots, but we did not observe an increase in Cu accumulation in CuWT DTY3 MATa; trp1-1; leu2-3; leu2-112; gal1, His2; ura3-50; cup1s (single copy) Hamer et al (1985) Dcup1 DTY4 MATa; trp1-1; leu2-3; leu2-112; gal1, His2; ura3-50; cup1TURA31 Hamer et al (1985) Dzrc1 Dcot1 CM137 MATa; can1-100; his3-11; his3-15; leu2-3; leu2-112; trp1-1; ura3-52; Dzrc1THIS3; Dcot1TKanR…”

AtCCS is a functional homolog of the yeast copper chaperone Ccs1/Lys7

“…The Arabidopsis COPT1 gene and its four homologs encode copper transporters that may allow the entrance of Cu into cells [5][6][7]. Copper is imported into the chloroplast stroma by the P-type ATPase PAA1 and mutations in PAA1 affect both stromal Cu/ZnSOD activity and PC [8].…”