AtHMA1 contributes to the detoxification of excess Zn(II) in Arabidopsis

Abstract

SUMMARYAtHMA1 is a member of the heavy metal-transporting ATPase family. It exhibits amino acid sequence similarity to two other Zn(II) transporters, AtHMA2 and AtHMA4, and contains poly-His motifs that are commonly found in Zn(II)-binding proteins, but lacks some amino acids that are typical for this class of transporters. AtHMA1 localizes to the chloroplast envelope. In comparison with wild-type plants, we observed a more pronounced sensitivity in the presence of high Zn(II) concentrations, and increased accumulation of Zn in the chloroplast of T-DNA insertional mutants in AtHMA1. The Zn(II)-sensitive phenotype of AtHMA1 knock-out plants was complemented by the expression of AtHMA1 under the control of its own promoter. The Zn(II)-transporting activity of AtHMA1 was confirmed in a heterologous expression system, Saccharomyces cerevisiae. The sensitivity of yeast to high concentrations of Zn(II) was altered by the expression of AtHMA1 lacking its Nterminal chloroplast-targeting signal. Taken together, these results suggest that under conditions of excess Zn(II), AtHMA1 contributes to Zn(II) detoxification by reducing the Zn content of Arabidopsis thaliana plastids.

The Role of Arabidopsis ABCG9 and ABCG31 ATP Binding Cassette Transporters in Pollen Fitness and the Deposition of Steryl Glycosides on the Pollen Coat

“…To observe promoter-GUS expression in flowers and developing siliques, T1 plants from 58 (ABCG9 pro :GUS) and 23 (ABCG31 pro :GUS) independent transgenic lines were stained with GUS staining solution as described by Kim et al (2009). In the case of ABCG9, most lines exhibited similar expression patterns.…”

“…Flowers and seedlings were incubated in GUS solution for 15 and 12 h, respectively. To observe GUS expression in specific floral tissues, GUS-stained flower buds were fixed and dehydrated as described by Kim et al (2009). The dehydrated samples were embedded in Technovit 7100 (Kulzer), and then serial sections (10-mm thick) were obtained using a Leica RM2245 rotary microtome.…”

A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

“…They are divided into two groups: zinc (Zn)/cadmium (Cd)/cobalt/lead (Pb) and copper (Cu)/silver transporters (Williams and Mills, 2005). AtHMA1 to AtHMA4 in A. thaliana and OsHMA1 to OsHMA3 in rice belong to the former group, while AtHMA5 to AtHMA8 and OsHMA4 to OsHMA9 belong to the latter group, although AtHMA1 has also been shown to transport Zn, Cu, and calcium (Axelsen and Palmgren, 2001;Williams and Mills, 2005;Seigneurin-Berny et al, 2006;Moreno et al, 2008;Kim et al, 2009).…”

“…AtHMA1 is involved in delivering Cu to the stroma, exporting Zn 2+ from the chloroplast, or as a Ca 2+ /heavy metal transporter to the intracellular organelle (Seigneurin-Berny et al, 2006;Moreno et al, 2008;Kim et al, 2009). AtHMA2 and AtHMA4 localized at the pericycle are partially redundant and responsible for the release of Zn into the xylem (xylem loading) as well as Cd (Hussain et al, 2004;Verret et al, 2004;, while AtHMA3 localized at the tonoplast plays a role in the detoxification of Zn/Cd/cobalt/Pb by mediating them into the vacuole (Morel et al, 2009;Chao et al, 2012).…”

Hydathode function and changes in contents of elements in eddo exposed to zinc in hydroponic solution

“…A portion of the powder (.1 g) was digested with 3-mL (70%, v/v) nitric acid in a sealed decomposition vessel in a microwave sequestered in vacuoles in the epidermal cells of Thlaspi caerulescens (Frey et al, 2000;Küpper et al, 1999) and accumulated in mesophyll cells in Arabidopsis halleri (Küpper et al, 2000;Zhao et al, 2000). Some plants compartmentalize excess Zn into central vacuoles (Maeshima, 2001;Martinoia et al, 2007) and chloroplasts (Kim et al, 2009), and/or entrap free Zn in the cytoplasm using small cysteine-rich proteins and peptides (Clemens, 2001;Cobbett, 2000;Haydon & Cobbett, 2007). Guttation can facilitate the excretion of boron (B) in banana (Shapira et al, 2013), calcium (Ca) in eddo (Islam & Kawasaki, 2015), and arsenic in Pteris vittata fronds (Cantamessa et al, 2015) when those elements are present at excessive concentrations.…”