Ancient Secret of Evolution Solved
What was the question behind this work? One of the building blocks for microtubules, a central element of the cytoskeleton that orients growth and division of plant cells, α-tubulin gets truncated at one end by the enzyme TTC, leading to a shorter version of the protein. The cleaved part, the amino acid tyrosine, can be ligated back through the enzyme TTL. The meaning of this circus is unclear - but since all tubulins from all life forms carry a tyrosine at their end, this phenomenon seems to be important.
How did we approach the question? We have now boosted TTL from rice and in tobacco cell using genetic engineering and then searched, how this will change the biology of the plants and cells. Our focus was on growth and development. We also purified and measured both forms of tubulin (with and without the terminal tyrosine) using a procedure developed in our laboratory.
What was the result? When the ligase TTL is boosted, this should allow more of the truncated tubulin to be complemented with a tyrosine. We observe just the opposite - there is more and not less of de-tyrosinated tubulin. The enzyme does just the opposite of that what would be expected from a TTL, it behaves like a TTC. On the cellular level this is accompanied by a problem with new cell walls that are inserted tilted and in a wavy manner. This problem during cell division has the consequence that the roots of these transgenic rice plants grow more slowly. Did we find in fact the for three decades elusive phantom of a plant TTC?
Publication 163. Zhang K, Durst S, Zhu X, Hohenberger P, Han MJ, An GH, Sahi V, Riemann M, Nick P (2021) A rice tubulin tyrosine ligase‐like 12 protein affects the dynamic and orientation of microtubules. J Int Plant Biol 63, 848-864 - pdf
E-nose Sniffing Mint Scent
What was the question behind this work? Plant scents are manifold and act precisely, manipulate insects, drive competitors into suicide and also exert various influences upon us humans. To be able to investigate this, one needs to distinguish them - this should be fast, reliable and objective. This is not only relevant for biology, but also for industry. The market of scents is exclusive and expensive. Deceit is part of everyday business.
How did we approach the question? Through a truly interdisciplinary cooperation between the Botanical Institute, the Institute for Light Technology, and the Institute for Functional Interfaces, a e-nose based upon the SURMOF technology was developed and validated. As case study, we picked the Mints - here, many and closely related species have developed in a kind of chemical evolution quite different scents.
What was the outcome? In the Botanical Garden of the KIT, a collection of authenticated Mint species was established, which was used to train the e-nose. The different olfactory receptor of the nose were replaced by different nanomaterials. Each scent binds differentially to these sensors and using a neural network strategy the system can be trained to recognise the fingerprint of each Mint scent. The nose trained in this way can then assign an unknown Mint to the correct species. A problem is still that the nose needs to be "washed" with fresh air for an hour to become ready for a new sniff. Currently, we work on new sensors that more rapidly return into the initial state - similar as a wine tester needs to swallow the mouth with mineral water between the testing.
Publication 164. Okur S, Sarheed M, Huber R, Zhang Z, Heinke L, Kanbar A, Wöll C, Nick P, Lemmer U (2021) Identification of Mint scents using a QCM based E-Nose. Chemosensors 9, 31. doi.org/10.3390/chemosensors9020031 - pdf
Wild Grapes Help Against Climate Change?
What was the topic behind this work? The hot and dry summers cause also in our region to break down grapes in the blossom of their productivity. The cause are wood colonising fungi that are also found in healthy grapes and act there as harmless commensalists. When their host is posed under stress, they suddenly change their behaviour and begin to produce toxins, zu kill their host and extract energy from its corpse to make sex, form fruiting bodies, break out from the wood and spread their spores. ("The rats leave the sinking ship") We wondered, whether we can find grapes that can cope better with this challenge.
How did we approach the question? The key for our research was the Wild Grape Collection established in the Botanical Garden of the KIT. This collection is unique worldwide, because it assembles the entire genetic diversity of the rare European Wild Grapevin (the ancestor of our domesticated Grapevine). In fact, several of these grapes can ward off the attack of wood decaying fungi. Using a connection of molecular, histocheical and Cryo SEM methods we investigated, how their defence works.
What did we get? We could show that fungus and plant run a chemical arm race. The formation of wood and the formation of defence compounds, so called stilbenes, compete for the same entry molecules. The fungus tries to manipulate the grape by chemical signals to make it accumulate as much wood as possible (which is the food for the fungus). The plant, instead, tries to boost the formation of stilbenes. The wild grapes are more powerful in this arm race and channel their metabolism in a way that the potent viniferin trimers are formed that can stop fungal growth. Our knowledge can now help to render grapes, but also city trees, against the consequences of climate change. Our work was published in the high-ranking journal New Phytologist. more...
Cellular Trojans Mitigate Salt Stress
What was the topic behind the work? By means of a wooden horse, the Greeks succeeded in entering Troy and conquer the city. Plant cells with their rigid cell wall are quite comparable to the fortress of Troy. To get it under control, usually genetic engineering is employed, introducing DNA into the genome that encodes the desired trait. Is there any other path to manipulate cells immediately, without the detour through the genes? This is what we tried successfully in this work:
How did we approach the question? In cooperation with the team of Ute Schepers (Institute for Toxicology and Genetics) our team succeeded to develop over the years “Chemical Trojans” that can target the mitochondria of plant cells, the organelles, where through respiration energy is generated. Oxygen is actually a risky matter for a cell, because easily reactive oxygen species can result that cause numerous damages. This happens especially, if the stress is exposed to stress and is, by the way, one of the reasons, why we humans often keep bodily damage from stress. Our Trojan Horse did not smuggle in blood-thirsty warriors, but a variant of Coenzyme Q10 that efficiently buffers reactive oxygen species.
What did we achieve? Not only could we demonstrate that pretreatment with this Trojan protects cells against salt stress, but we also cleared up, how this Trojan reaches the heart of the mitochondria. Different from the original concept, this tool does not sneak through the cell membrane, but is taken up with vesicles that pass on their cargo to the endoplasmic reticulum, until the Trojan reaches to the door of the mitochondria. Only here, it permeates the membrane. This is important, because plant cells respond to perturbed integrity of their cell membrane by programmed cell death, a kind of cellular suicide (that, among other purposes, prevents invasions of pathogens). This problem is elegantly circumvented by our "mitochondrial Trojan".
148. Asfaw KG, Liu Q, Maisch J, Münch S, Wehl I, Bräse S, Bogeski I, Schepers U, Nick P (2019) A Peptoid Delivers CoQ-derivative to Plant Mitochondria via Endocytosis. Nature Sci Rep 9, 9839 - pdf