Felix Rehms's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Westfälische Wilhelms-Universität Münster in the year 2019.
Development and application of genetically encoded fluorescent sensors for hypoxia investigation in plants
Rehms documents the visualization of Ca2+-accumulation in energy-deprived cells and the subsequent calcium signal propagation in Arabidopsis thaliana seedlings during prolonged oxygen restriction. He also started the development of genetically coded fluorescent oxygen sensors for use in-planta.
With regards to the growing frequency of extreme precipitation and flooding events caused by global climate changes, tolerance to oxygen deprivation (hypoxia; assumedly the most severe plant stress caused by prolonged submergence) is rapidly gaining relevance as a trait in crop breeding, even though, as of yet, the underlying mechanisms are mostly unknown.
To shed light on the role of second messengers in a plant’s perception and signal transduction of hypoxic conditions or the resulting energy crisis (caused by inhibition of aerobic respiration), genetically encoded fluorescent sensors of cytosolic Ca2+ and ATP concentration were employed for microscopic investigation of submerged Arabidopsis thaliana seedlings in a spatio-temporal resolution.
This way, he was able to record multiple waves of Ca2+-elevations, which were assumedly triggered by the collapse of energy upkeep and subsequent breakdown of active transport mechanisms that ensured the upkeep of steep ion gradients across membranes. Starting from the first energy depleted tissues or cells this wave spreads outwards and across the full seedling. The dynamics of these waves and comparisons to ATP monitoring in hypoxic seedlings suggests active signal propagation, rather than a universal increase caused exclusively by energy deprivation and passive ion leakage.
Additionally, this work documented the beginning development of genetically coded fluorescent oxygen indicators. Such oxygen sensors can be ubiquitously expressed in all tissues and can be applied in-vivo to monitor ongoing developments. In contrast to chemical and physical oxygen measurements, this does not cause any additional plant stress. This makes the fluorescent sensors ideal for the investigation of the oxygen dependency of signals in hypoxic plants. On top of that, the sensors’ independence of plant adaption or developmental mechanisms may lead to the identification of hypoxic niches that were not implicated by expression of hypoxia marker genes.
Felix Rehms conducted this work at the institute of Plant Biology and Biotechnology (IBBP) in the group of Prof. Dr. Jörg Kudla.