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CELL BIOLOGY AND SIGNAL TRANSDUCTION

ECA3, a Golgi-Localized P_2A-Type ATPase, Plays a Crucial Role in Manganese Nutrition in Arabidopsis^{1,[C],[W],[OA]}

School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom (R.F.M., M.L.D., L.E.W.); Centre for Membrane Pumps in Cells and Disease, Danish National Research Foundation, Department of Plant Biology, University of Copenhagen, DK–1871 Frederiksberg, Denmark (R.L.L.-M., M.G.P.); Department of Biochemistry, Downing Site, Cambridge CB2 1QW, United Kingdom (T.W., P.D.); and Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom (J.K.P.)

Calcium (Ca) and manganese (Mn) are essential nutrients required for normal plant growth and development, and transport processes play a key role in regulating their cellular levels. Arabidopsis (Arabidopsis thaliana) contains four P_2A-type ATPase genes, AtECA1 to AtECA4, which are expressed in all major organs of Arabidopsis. To elucidate the physiological role of AtECA2 and AtECA3 in Arabidopsis, several independent T-DNA insertion mutant alleles were isolated. When grown on medium lacking Mn, eca3 mutants, but not eca2 mutants, displayed a striking difference from wild-type plants. After approximately 8 to 9 d on this medium, eca3 mutants became chlorotic, and root and shoot growth were strongly inhibited compared to wild-type plants. These severe deficiency symptoms were suppressed by low levels of Mn, indicating a crucial role for ECA3 in Mn nutrition in Arabidopsis. eca3 mutants were also more sensitive than wild-type plants and eca2 mutants on medium lacking Ca; however, the differences were not so striking because in this case all plants were severely affected. ECA3 partially restored the growth defect on high Mn of the yeast (Saccharomyces cerevisiae) pmr1 mutant, which is defective in a Golgi Ca/Mn pump (PMR1), and the yeast K616 mutant (pmc1 pmr1 cnb1), defective in Golgi and vacuolar Ca/Mn pumps. ECA3 also rescued the growth defect of K616 on low Ca. Promoter:β-glucuronidase studies show that ECA3 is expressed in a range of tissues and cells, including primary root tips, root vascular tissue, hydathodes, and guard cells. When transiently expressed in Nicotiana tabacum, an ECA3-yellow fluorescent protein fusion protein showed overlapping expression with the Golgi protein GONST1. We propose that ECA3 is important for Mn and Ca homeostasis, possibly functioning in the transport of these ions into the Golgi. ECA3 is the first P-type ATPase to be identified in plants that is required under Mn-deficient conditions.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Lorraine E. Williams (l.e.williams{at}soton.ac.uk).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.107.110817

^* Corresponding author; e-mail l.e.williams{at}soton.ac.uk.

Received October 15, 2007; accepted November 11, 2007; published November 16, 2007.