An Endoplasmic Reticulum-Bound Ca²⁺/Mn²⁺Pump, ECA1, Supports Plant Growth and Confers Tolerance to Mn²⁺ Stress

Journal Article · Tue Jan 01 00:00:00 EST 2002 · Plant Physiology

DOI:https://doi.org/10.1104/pp.004440· OSTI ID:932548

Z, Wu; Liang, F; Hong, B; Young, JC; Sussman, MR; Harper, JF; Sze, and H

Plants can grow in soils containing highly variable amounts of mineral nutrients, like Ca²⁺ and Mn²⁺, though the mechanisms of adaptation are poorly understood. Here we report the first genetic study to determine in vivo functions of a Ca²⁺ pump in plants. Homozygous mutants of Arabidopsis thaliana harboring a T-DNA disruption in ECA1 showed a 4-fold reduction in ER-type calcium pump activity. Surprisingly, the phenotype of mutant plants was indistinguishable from wild-type when grown on standard nutrient medium containing 1.5 mM Ca²⁺ and 50 μM Mn²⁺. However, mutants grew poorly on medium with low (0.2 mM) Ca²⁺ or high (0.5 mM) Mn²⁺. On high Mn²⁺, the mutants failed to elongate their root hairs, suggesting impairment in tip growth processes. Expression of the wild-type gene (CAMV35S::ECA1) reversed these conditional phenotypes. The activity of ECA1 was examined by expression in a yeast mutant, K616, which harbors a deletion of its endogenous calcium pumps. In vitro assays demonstrated that Ca²⁺, Mn²⁺ and Zn²⁺ stimulated formation of a phosphoenzyme intermediate, consistent with the translocation of these ions by the pump. ECA1 provided increased tolerance of yeast mutant to toxic levels of Mn²⁺ (1 mM) and Zn²⁺(3mM), consistent with removal of these ions from the cytoplasm. These results show that despite the potential redundancy of multiple Ca²⁺ pumps and Ca²⁺/H⁺ antiporters in Arabidopsis, pumping of Ca²⁺ and Mn²⁺ by ECA1 into the endoplasmic reticulum is required to support plant growth under conditions of Ca²⁺ deficiency or Mn²⁺ toxicity.

• Research Organization: University of Maryland, College Park, MD
• Sponsoring Organization: USDOE - Office of Energy Research (ER)
• DOE Contract Number: FG02-95ER20200
• OSTI ID: 932548
• Report Number(s): DOE/ER/20200-1
• Journal Information: Plant Physiology, Vol. 130
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
Calcium pump
ATPase
Plant growth
Mn tolerance
Arabidopsis
ER