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Dr. Stefanie Höller

Research and teaching

During my undergraduate and graduate studies of Biology at the University of Bonn, I focused mainly on plant stress physiology. My final year project was concerned with the regulation of aldehyde dehydrogenases in the model plant Arabidopsis. After graduation, I moved my interests to plant nutrition and stress responses in crops and started my PhD project at the Department of Plant Nutrition (INRES) in Bonn. I focused on the ascorbate metabolism in rice and its importance and relevance under different stress conditions, like zinc (Zn) deficiency, ozone stress, iron (Fe) toxicity, and oxidative stress in general. We were able to comfirm that ascorbate served as an efficient tolerance factor against Zn deficiency and ozone stress, but not Fe toxicity, and enhanced plant fitness even under non-stressed conditions. Moreover, enhanced ascorbate biosynthesis could be related to tolerance to Zn deficiency in a recombinant inbred line, while reduced recycling or degradation was not a limiting factor.

At Halle, I have moved from Zn to manganese (Mn) in plants, and returned to Arabidopsis. Manganese (Mn) deficiency can be observed frequently on alkaline soils and results in interveinal chlorosis and severe defects in the plant since Mn is part of the photosynthetic oxygen evolving complex and a cofactor of many enzymes. On the other hand, Mn toxicity leads to severe problems for plant growth especially on acidic and waterlogged soils. To ensure the Mn balance under different conditions of Mn availability, transport processes are of great importance. Metal Tolerance Proteins (MTPs) are an important family of metal transporters. In Arabidopsis, four members of the Cation Diffusion Facilitator (CDF) family are involved in Mn transport. Only two of them have been described so far, both by people of our lab: MTP11 confers Mn tolerance by loading Mn into the Golgi apparatus (Peiter et al., 2007); MTP8, localized at the tonoplast, protect plants from Mn toxicity and secures Fe acquisition during Fe deficiency (Eroglu et al. 2016), and also mediates storage of Mn in developing seeds (Eroglu et al., 2017). In my current projects, I investigate the mechanisms behind the role of AtMTP8 in Fe acquisition and seed development, and I elucidate the physiological roles of yet uncharacterized members of the MTP family in Arabidopsis. For example, our ongoing work has shown that MTPs also impacts on Mn and Fe translocation under different conditions of nutrient supply.

In addition to conducting research myself, I supervise research internships and final year projects of bachelor and master students. I also participate in the teaching programme of the group. My courses mainly introduce students to molecular and physiological methods in physiological plant nutrition research on undergraduate and graduate level.

Publications

Fu D, Zhang Z, Wallrad L, Wang Z, Höller S, Ju C, Schmitz-Thom I, Huang P, Peiter E, Kudla J, Wang C (2022). Ca²⁺-dependent phosphorylation of NRAMP1 by CPK21 and CPK23 facilitates manganese uptake and homeostasis in Arabidopsis. Proceedings of the National Academy of Sciences of the USA 119, e2204574119.

Höller S, Küpper H, Brückner D, Garrevoet J, Spiers K, Falkenberg G, Andresen E, Peiter E (2022). Overexpression of METAL TOLERANCE PROTEIN8 reveals new aspects of metal transport in Arabidopsis thaliana seeds. Plant Biology 24, 23-29.

Alejandro S, Höller S, Meier B, Peiter E (2020). Manganese in plants: from acquisition to subcellular allocation. Frontiers in Plant Science 11, 300.

Höller S, Ueda Y, Wu L, Wang Y, Hajirezaei MR, Ghaffari MR, von Wirén N, Frei M (2015). Ascorbate biosynthesis in rice (Oryza sativa L.) and its involvement in stress tolerance and plant development. Plant Molecular Biology 88, 545-560.

Ueda Y, Frimpong F, Qi Y, Matthus E, Wu L, Höller S, Kraska T, Frei M (2014). Genetic dissection of ozone tolerance in rice (Oryza sativa L.) by genome wide association study. Journal of Experimental Botany 66, 293-306.

Matthus E, Wu LB, Ueda Y, Höller S, Becker M, Frei M (2015). Loci, genes, and mechanisms associated with tolerance to ferrous iron toxicity in rice (Oryza sativa L.). Theoretical and Applied Genetics 128, 2085-2098.

Höller S, Hajirezaei MR, von Wirén N, Frei M (2014). Ascorbate metabolism in rice genotypes differing in zinc efficiency. Planta 239, 367-379.

Höller S, Meyer A, Frei M (2014). Zinc deficiency differentially affects redox homeostasis of rice genotypes contrasting in ascorbate level. Journal of Plant Physiology 171, 1748-1756.

CV

Awards

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