Mn tolerance in rice is mediated by MTP8.1, a member of the cation diffusion facilitator family

Abstract

Manganese (Mn) is an essential micronutrient for plants, but is toxic when present in excess. The rice plant (Oryza sativa L.) accumulates high concentrations of Mn in the aerial parts; however, the molecular basis for Mn tolerance is poorly understood. In the present study, genes encoding Mn tolerance were screened for by expressing cDNAs of genes from rice shoots in Saccharomyces cerevisiae. A gene encoding a cation diffusion facilitator (CDF) family member, OsMTP8.1, was isolated, and its expression was found to enhance Mn accumulation and tolerance in S. cerevisiae. In plants, OsMTP8.1 and its transcript were mainly detected in shoots. High or low supply of Mn moderately induced an increase or decrease in the accumulation of OsMTP8.1, respectively. OsMTP8.1 was detected in all cells of leaf blades through immunohistochemistry. OsMTP8.1 fused to green fluorescent protein was localized to the tonoplast. Disruption of OsMTP8.1 resulted in decreased chlorophyll levels, growth inhibition in the presence of high concentrations of Mn, and decreased accumulation of Mn in shoots and roots. However, there was no difference in the accumulation of other metals, including Zn, Cu, Fe, Mg, Ca, and K. These results suggest that OsMTP8.1 is an Mn-specific transporter that sequesters Mn into vacuoles in rice and is required for Mn tolerance in shoots.

The Vacuolar Manganese Transporter MTP8 Determines Tolerance to Iron Deficiency-Induced Chlorosis in Arabidopsis

“…6). Mn specificity and vacuolar localization were recently also demonstrated for MTP8 orthologs in cucumber (Cucumis sativus; Migocka et al, 2014) and rice (Oryza sativa; Chen et al, 2013). The function of MTP8 to sequester Mn into vacuoles, therefore, is widely conserved across species, with the possible exception of barley (Hordeum vulgare), where MTP8 homologs have been localized to the Golgi apparatus (Pedas et al, 2014).…”

Characterization of a cDNA from Beta maritima that confers nickel tolerance in yeast

“…These two proteins have also been shown to localize and function in similar patterns to those Mtp11 proteins (Erbasol et al, 2013). Finally, in a very recently published study, researchers identified OsMTP8.1, which is the rice homolog of AtMTP11, and reported that OsMTP8.1 confers manganese tolerance via vacuole sequestering of the same element (Chen et al, 2013).…”

“…Recent studies on manganese tolerance clearly show the robustness of cDNA library based studies to identify heavy metal detoxification genes in plant species (Chen et al, 2013;Erbasol et al, 2013;Papoyan and Kochian, 2004;Pence et al, 2000). Apart from that, these studies have also shown the evolutionary importance and convergence of the secretory pathway proteins' significant involvement on the heavy metal detoxification (Chen et al, 2013;Erbasol et al, 2013;Peiter et al, 2007).…”

“…Apart from that, these studies have also shown the evolutionary importance and convergence of the secretory pathway proteins' significant involvement on the heavy metal detoxification (Chen et al, 2013;Erbasol et al, 2013;Peiter et al, 2007). Even though all these different plants do not share the same environment, and adapted to different levels of soil manganese levels, they all do have similar mechanism, and even share highly identical protein sequences to cope with heavy metal stress (Chen et al, 2013;Erbasol et al, 2013;Peiter et al, 2007).…”

Altered Expression of a Malate-Permeable Anion Channel, OsALMT4, Disrupts Mineral Nutrition

“…Expression of OsMTP8.1, a member of the cation diffusion facilitator family, tended to be greater in OX5 than in null plants as well. OsMTP8.1 localizes to the tonoplast of leaf cells and appears to be important for loading Mn into the vacuole, since it is induced by Mn toxicity (Chen et al, 2013). Other transporters encoded by OsYSL6 and OsMTP9 have been shown previously not to change expression with Mn supply (Sasaki et al, 2011;Ueno et al, 2015).…”