Plant H+-ATPase regulation in biotic and abiotic stress

PhD Defence by Peter Klemmed Bjørk

Summary:

The plant plasma membrane (PM) H+-ATPase is responsible for transport of protons from the inside of the cell to the outside, which facilities uptake of nutrients as nutrient uptake is coupled to proton transport. Furthermore, acidification of the apoplast is crucial to loosening of the cell wall structure, which is required for cell elongation. The plant plasma membrane H+-ATPase therefore plays a central role in both nutrient uptake and cell growth. It has previously been demonstrated that several microorganisms target this enzyme and we hypothesize that the central role has made the PM H+-ATPase a common target for plant-associated microorganisms. Understanding the mechanisms involved in plant-microbe association harbors great potential for future agricultural exploitation.
During my PhD work, I have applied a bioassay-guided approach to identify fungal modulators of the plant PM H+-ATPase. Extracted fungal metabolites were separated in fractions and screened for their effect on ATPase activity, following interesting fractions were further separated and analyzed in an iterative process. By this approach I identified two different plant PM H+-ATPase modulators from plant-associated fungi. Tenuazonic acid from Stemphylium loti was found to be a very specific inhibitor of the H+-ATPase. Peptaibols, originating from Trichoderma harzianum, were found to increase H+-ATPase activity by loosening the lateral pressure of the membrane.
Both fungi gain an advantage by manipulating host plant metabolism, however, the exact nature of the relationship between plant and microorganism is poorly understood.

Supervisor:

Associate Professor Anja Thoe Fuglsang, Transport Biology

Assessment Committee:

Professor Claudia Oecking, University of Tübingen, Germany
Associate Professor Natalya Fedosova, Aarhus University
Professor Michael Broberg Palmgren, PLEN (chair)

Reception afterwards in the Konsistoriesal next to the Festauditorium​​