The vacuolar transporterLaMTP8.1 detoxifies manganese in leaves ofLupinus albus

Abstract

Manganese (Mn) is an essential microelement, but overaccumulation is harmful to many plant species. Most plants have similar minimal Mn requirements, but the tolerance to elevated Mn varies considerably. Mobilization of phosphate (P) by plant roots leads to increased Mn uptake, and shoot Mn levels have been reported to serve as an indicator for P mobilization efficiency in the presence of P deficiency. White lupin (Lupinus albus L.) mobilizes P and Mn with outstanding efficiency due to the formation of determinate cluster roots that release carboxylates. The high Mn tolerance of L. albus goes along with shoot Mn accumulation, but the molecular basis of this detoxification mechanism has been unknown. In this study, we identify LaMTP8.1 as the transporter mediating vacuolar sequestration of Mn in the shoot of white lupin. The function of Mn transport was demonstrated by yeast complementation analysis, in which LaMTP8.1 detoxified Mn in pmr1∆ mutant cells upon elevated Mn supply. In addition, LaMTP8.1 also functioned as an iron (Fe) transporter in yeast assays. The expression of LaMTP8.1 was particularly high in old leaves under high Mn stress. However, low P availability per se did not result in transcriptional upregulation of LaMTP8.1. Moreover, LaMTP8.1 expression was strongly upregulated under Fe deficiency, where it was accompanied by Mn accumulation, indicating a role in the interaction of these micronutrients in L. albus. In conclusion, the tonoplast‐localized Mn transporter LaMTP8.1 mediates Mn detoxification in leaf vacuoles, providing a mechanistic explanation for the high Mn accumulation and Mn tolerance in this species.

Cation diffusion facilitator proteins of Beta vulgaris reveal diversity of metal handling in dicotyledons

“…While BvMTP8.1 is localized in the tonoplast, BvMTP8.2 shows a punctate localization pattern. Localization of MTP8 proteins has been observed before to differ between species: tonoplast‐localized MTP8 homologs in Arabidopsis, rice, and white lupin are implicated in vacuolar Mn sequestration (Chen et al, 2013; Eroglu et al, 2016; Olt et al, 2022; Takemoto et al, 2017), while in barley, HvMTP8.1 and HvMTP8.2 are located in the Golgi with unknown function (Pedas et al, 2014). So far sugar beet is the only plant with two differently localized MTP8 proteins, indicating a diversification in their roles.…”

“…The rice orthologs OsMTP8.1 and OsMTP8.2 have also been characterized as transporters implicated in vacuolar Mn sequestration, albeit not related to the Fe deficiency response (Chen et al, 2013; Takemoto et al, 2017). In Lupinus albus , which mobilizes large amounts of Mn by P‐starvation‐induced root exudates, LaMTP8 detoxifies Mn in leaf vacuoles (Olt et al, 2022). In contrast to the vacuolar MTP8 proteins, the barley orthologs HvMTP8.1 and HvMTP8.2 have been localized to the Golgi (Pedas et al, 2014).…”

Effect of sewage sludge and digestate from anaerobic fermentation as soil additives on the nutritional status and accumulation of non-essential elements in plants with different nutrition strategies

“…Some P-e cient species, of which Lupinus albus and species from the Proteaceae have been the most profoundly studied, hyper-accumulate manganese under conditions of P-de ciency. When P-supply is low, the species release large quantities of carboxylates, especially citrate and malate (Lambers et al 2015;Lambers et al 2022 in the soil which is accompanied by the upregulation of transition metal transporters that e ciently transport Mn to the shoots and store it in leaf vacuoles (Lambers et al 2015;Olt et al 2022). The carboxylates mobilize not only phosphate and Mn but also a variety of non-essential elements (Wiche and Pourret 2023; ).…”