Ronja Rüdel (Salzburg University)
Ronja Rüdel's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Paris Lodron University Salzburg in the year 2021
Title: "Experimental evolution of zinc tolerance in Pseudomonas syringae infecting zinc accumulating plants"
This study provides evidence that pathogens can rapidly evolve higher zinc tolerances in vitro and are therefore able to infect plants, which have accumulated increased concentrations of zinc. This result supports the Elemental Defence Hypothesis and reveals a connection between plant pathogens and the evolutionary trait of metal hyperaccumulation in plants.
The enhanced uptake and storage of heavy metals in plants may function as a protection mechanism of the plant against herbivores or pathogens, which is known as the “elemental defence hypothesis”. This study aimed to investigate the ability of plant pathogens to coevolve with hyperaccumulating plants by adapting to altered metal concentrations.
In this study, in vitro experimental evolution of a Pseudomonas syringae pv. maculicola standard laboratory strain was performed to possibly evolve strains exhibiting increased zinc tolerance. Further, in vitro assessment of zinc tolerance of the evolved bacterial strains was conducted to characterize enhanced zinc tolerances. This was followed by in planta infection assays to investigate the ability of the evolved, zinc tolerant bacterial strains to infect the zinc accumulating plant Noccaea caerulescens.
The results of this study provide evidence that it is possible to evolve strains towards higher zinc tolerance in only few rounds of experimental evolution. The evolved strains were able to infect plants, which had accumulated intermediate to high concentrations of zinc, while the original Pseudomonas syringae strain showed reduced growth rates in those plants. These results support the “elemental defence hypothesis” and reveal coevolutionary processes in plant pathogens adapting to metal hyperaccumulating plants.
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Ronja Rüdel conducted this project under supervision by Dr. Anja Hörger in the group of Prof. Hans-Peter Comes at the Department of Biosciences at the University of Salzburg.