Establishing a plastid ionome to investigate plant organellar nutrient homeostasis

Holzner, Lorenz (2026): Establishing a plastid ionome to investigate plant organellar nutrient homeostasis. Dissertation, LMU München: Faculty of Biology

Abstract

Plants require a defined set of mineral nutrients for optimal growth, development, and metabolic function, which can be separated into macronutrients (N, P, K, Ca, Mg, S) and micronutrients (Fe, Mn, Ni, Cu, Zn, B, Mo, Cl). The sum of all plant mineral nutrients is termed the plant ionome. At a tissue level, a shoot, root, and seed ionome has been established. The respective ionome can be used to identify novel and probe proposed candidates of plant nutrient homeostasis. However, at a subcellular level, ionomes of the plant organelles, plastid and mitochondria, are missing. Additionally, many transporters of plant nutrients at the organelles have not been identified. The plastid with its high demand for metal nutrients is of special interest. To overcome these limitations, this thesis utilizes the plastid ionome to investigate the Fe and K uptake and homeostasis at the plastid. In the first study, a plastid ionome of A. thaliana, A. halleri, N. benthamiana, and P. sativum was established at standard growth conditions. Additionally, the plastid ionome of the Fe and other metal accumulator mutant opt3 was utilized to probe plastid Fe import candidates at elevated Fe conditions. In the second study, a partial overlap in the function of KEA1/2 plastid inner envelope K+/H+ exchanger and MSL2/3 cation channels was identified. Here, combined loss of KEA1 and MSL2 displayed an additive phenotype, which was distinct from kea1kea2 and msl2msl3 phenotypes. In the third study, the ParXY system was identified as an additional secretion system of the siderophore pyoverdine in Pseudomonas putida. ParXY is crucial for growth at Fe-limiting conditions if other pyoverdine secretion systems are inactive. In the fourth study, it was shown that the CPP1 homologue CPL3 localizes exclusively to plastids, and not to the endomembrane system as proposed previously. CPL3 might have a function in the Fe homeostasis of plastids, as the Fe content of cpl3 mutants is elevated by trend.

• Item Type: Theses (Dissertation, LMU Munich)
• Subjects: 500 Natural sciences and mathematics; 500 Natural sciences and mathematics > 570 Life sciences
• Faculties: Faculty of Biology
• Language: English
• Date of oral examination: 19. May 2026
• 1. Referee: Kunz, Hans-Henning
• Signature of the printed copy: 0001/UMC 32149