OsMTP11 is localised at the Golgi and contributes to Mn tolerance

Abstract

Membrane transporters play a key role in obtaining sufficient quantities of manganese (Mn) but also in protecting against Mn toxicity. We have characterized OsMTP11, a member of the Cation Diffusion Facilitator/Metal Tolerance Protein (CDF/MTP) family of metal cation transporters in Oryza sativa. We demonstrate that OsMTP11 functions in alleviating Mn toxicity as its expression can rescue the Mn-sensitive phenotype of the Arabidopsis mtp11-3 knockout mutant. When expressed stably in Arabidopsis and transiently in rice and tobacco, it localises to the Golgi. OsMTP11 partially rescues the Mn-hypersensitivity of the pmr1 yeast mutant but only slightly alleviates the Zn sensitivity of the zrc1 cot1 yeast mutant. Overall, these results suggest that OsMTP11 predominantly functions as a Mn-transporting CDF with lower affinity for Zn. Site-directed mutagenesis studies revealed four substitutions in OsMTP11 that appear to alter its transport activity. OsMTP11 harbouring a substitution of leucine 150 to a serine fully rescued pmr1 Mn-sensitivity at all concentrations tested. The other substitutions, including those at conserved DxxxD domains, reduced complementation of pmr1 to different levels. This indicates their importance for OsMTP11 function and is a starting point for refining transporter activity/specificity.

Manganese in Plants: From Acquisition to Subcellular Allocation

“…By contrast, the overexpression of OsMTP11 enhanced Mn tolerance of rice and decreased the accumulation of Mn in shoots and roots (Ma et al, 2018). Stable expression of OsMTP11-GFP in Arabidopsis and transient expression of this construct in rice and tobacco protoplasts showed that OsMTP11 was also located to the Golgi (Figure 3B; Farthing et al, 2017). However, recent studies suggested that OsMTP11 localized to the trans-Golgi network (TGN) when it was expressed in rice protoplasts and tobacco epidermal cells (Ma et al, 2018).…”

Genome-Wide Identification, Comprehensive Gene Feature, Evolution, and Expression Analysis of Plant Metal Tolerance Proteins in Tobacco Under Heavy Metal Toxicity

“…Both OsMTP8.1 and OsMTP8.2 were tonoplast-localized Mn transporters, and OsMTP9 was involved in efficient root Mn uptake (Chen et al, 2013; Ueno et al, 2015; Takemoto et al, 2017; Tsunemitsu et al, 2018b). Moreover, OsMTP11 played a crucial role in Mn tolerance through intracellular Mn compartmentalization, although the correct localization of this protein was still under debate (Farthing et al, 2017; Zhang and Liu, 2017; Ma et al, 2018; Tsunemitsu et al, 2018a). In addition, some MTP proteins from cucumber were recently isolated and their corresponding substrates were also specified.…”

Molecular mechanisms of plant adaptive responses to heavy metals stress

“…However, there are indications that the organelle is indeed implicated. Farthing et al (2017) showed the member of the CDF/MTP family in Oryza sativa , OsMTP11, in alleviating Mn toxicity. Moreover, the expression of OsMTP11 gene can save the Arabidopsis mtp11‐3 knockout mutant, the Mn‐sensitive phenotype.…”

“…It slightly alleviates the Zn sensitivity of the zrc1 cot1 yeast mutant and partially rescues the Mn-hypersensitivity of the pmr1 yeast mutant. Therefore, it is possible to suggest that OsMTP11 mostly functions as a Mn-CDF transporter with lower affinity for Zn (Farthing et al, 2017). It was shown that in 5-day-old seedlings of H. vulgare cv.…”