Manganese homeostasis and detoxification in plants: the role of Cation Diffusion Facilitators
Final Report Abstract
Manganese (Mn) is an essential element for plants; it plays crucial roles in the water-splitting complex of photosystem II and as cofactor of many enzymes. Conversely, a high availability of Mn in the soil can cause toxicity symptoms. Both, limiting and excessive Mn availability can therefore severely limit crop growth and productivity. The efficiencies of Mn use and Mn detoxification are largely determined by the uptake, translocation, and intracellular distribution of the metal. As these processes involve the transport of Mn across cellular membranes, Mn transporters are principal players in Mn homeostasis. The Cation Diffusion Facilitator (CDF) / Metal Tolerance Protein (MTP) gene family encodes metal transport proteins, some of which are good candiates for Mn transporters. It was the general objective of this project to reveal roles of those proteins in Mn homeostasis and detoxification. To this end, we studied their selectivites and transport activities by heterologous expression in yeast mutants, their expression patterns by using qPCR and promoter-reporter-gene fusions, and their subcellular localization by using fluorescent fusion proteins. T-DNA insertional mutants, complementation lines, and overexpressor lines were obtained or generated to analyse the function of those CDFs in Mn-dependent processes and their effect on Mn translocation and accumulation. All examined proteins restored the growth of a Mn-sensitive yeast strain on high Mn medium, but did not complement yeast strains sensitive to other metals. For two of the proteins, their Mn transport activity was directly shown in vesicle flux assays. One member of the family was localized to the tonoplast, implying that this protein transports Mn into the vacuole. The finding that that knockout mutants for this gene were not only hypersensitive to high Mn, but also to low Fe availability, are indicative of a crucial function of this protein in alleviating Fe-Mn antagonism. Subcellular localization of another family member suggested that it functions in secretory Mn export from the cell. Its specific expression in the root pericycle suggested a role in xylem loading of Mn. Accordingly, knockout mutants were hypersensitive to low Mn supply, contained less Mn in the shoot, and showed a temporarily decreased Mn translocation via the xylem. This mutant was also hypersensitive to post-submergence stress, which was found to be associated with the transporter's role in xylem loading. The advancement of our understanding of the role of CDF transporters in plant Mn homeostasis provides a basis to improve this process in crop plants by biotechnological means or marker-based selection.
Publications
- (2010). Novel Manganese Transporters in Plants: Jacks of many trades. Genetics of Plant Mineral Nutrition, 30 September - 2 October 2010, Hannover, Germany
Meier B, Chen X, Gwinner A, Peiter-Volk T, Peter K, Peiter E
- (2011). Three Novel Transporters: Guiding manganese to the destined place. Annual Meeting of the German Society of Plant Nutrition, 27-29 September 2011, Kiel, Germany
Meier B, Chen X, Gwinner A, Höroldt M, Peter K, Thor K, Peiter E
- (2012). An intracellular manganese transporter required for submergence tolerance of Arabidopsis. Challenges for Plant Nutrition in Changing Environments: International Workshop and Meeting of the German Society of Plant Nutrition, 05-08 September 2012, Bonn, Germany. AND Annual Meeting of the German Society of Plant Nutrition, 9-10 May 2013, Weihenstephan, Germany
Meier B, Chen X, Peiter-Volk T, Peter K, Mustroph A, Peiter E
- (2013). A vascular manganese and iron transporter required for submergence tolerance of Arabidopsis. XVII. International Plant Nutrition Colloquium, 19-22 August 2013, Istanbul, Turkey
Meier B, Kirsten A, Fierlbeck L, Nies D, Mustroph A, Peiter E
- (2013). Characterization of a Mn transporter essential for Fe efficiency in Arabidopsis thaliana. XVII. International Plant Nutrition Colloquium, 19-22 August 2013, Istanbul, Turkey
Eroğlu S, Meier B, von Wirén N, Peiter E
- (2014). A manganese transporter essential for iron deficiency in Arabidopsis. 17th International Symposium on Iron Nutrition and Interactions in Plants, 6-10 July 2014, Gatersleben, Germany. AND Plant Nutrition 2014: International Conference of the German Society of Plant Nutrition, 10-12 September 2014, Halle (Saale), Germany
Eroğlu S, Meier B, von Wirén N, Peiter E
- (2014). Survival of Arabidopsis under post-anoxia conditions depends on a vascular manganese transporter. 17th International Symposium on Iron Nutrition and Interactions in Plants, 6-10 July 2014, Gatersleben, Germany
Meier B, Fierlbeck L, Kirsten A, Nies D, Mustroph A, Peiter E
- The vacuolar manganese transporter MTP8 determines tolerance to Fe deficiency-induced chlorosis in Arabidopsis. Plant Physiology, February 2016, 50 S.
Eroglu S, Meier B, von Wirén N, Peiter E
(See online at https://doi.org/10.1104/pp.15.01194)
