Health as ecological phenomenon

Around 150 years ago, Jahren Robert Koch succeeded to identify the cause of tuberculosis using a simple and convincing postulate. A microbe that is always found together with symptom, but is absent, when the symptoms are absent, must be the cause. However, the novel, climate-change promoted Grapevine Trunk Diseases ignore the Koch Postulate: the suspicious fungi are also found in the wood of healty plants without the presence of symptoms. In our previous work, we were able to work out experimental systems to study infection under controlled lab conditions, and could demonstrate that the fungi manipulate plant immunity by chemical signals and are also able to sense when the plant suffers from climate stress. In frame of the project "Microbes 4 Future" funded by the KIT presidium fund, we tried to understand the complex reality in the real-world vineyard. These diseases used to occur only sporadically in the past, but have become epidemic in consequence of climate change and now cause immense economic damage. Along the entire Upper Rhine Valley our colleague Dr. Islam Khattab sampled soil from the rhizosphre of diseased vines along with healthy plants from the same vineyard. After isolating and sequencing the DNA from this soil, cutting-edge bioinformatics allowed to reconstract the microbiome. To our surprise, the suspicious fungi also occurred on healthy vines, but here, they do not connect with each other. Instead, the outbreak of the disease is heralded by these fungi teaming up. Thus, disease is not a question of presence or absence of specific microbes, but rather the result of perturbed microbial ecology. This work has now appeared in the journal Plant Soil:

226. Khattab IM, Magold T, Lenk F, Sturm G, Flubacher N, Kaster AK, Nick P (2026) Health or disease – a question of rhizomicrobial ecology? The case of grapevine trunk disease. Plant Soil 522, 697–714 - pdf

Biohacking with Pyriculol

Around half of the life forms on this planet live as parasites. The unvoluntary "hosts" fight back by immune systems. Also plants are endowed with immunity that is, however, completely different from ours. The complexity is comparable though and arose from an evolutionary arm race between plants and parasites. First, there is a broad basal immunity acting against entire groups of organisms (such as all bacteria or all fungi). However, evolution is a flow, meaning that plant pathogens evolved signals, termed effectors that can turn off the stress hormone jasmonate and, thus, basal immunity.  In a next round of arm race, plants developed proteins that are able to sense such manipulative signals and re-install immunity. Often, as a last  resort, triggered by salicylic acid (by the way the natural precursor of aspirine) the infected cell will commit suicide to pull the invader into death, by this protecting the neighbouring cells. We show in this study that the causative agent of Rice Blast, a fungal disease with massive impact on food security in many Asian countries, has invented a novel, devilishly sophisticated method to "hack" the immune system of its host. The fungus produces the polyketide Pyriculol that is a structural mimic of salicylic acid. This imitation meticulously evades important aspects of salicylic acid, though. While cell death is activated and the basal immunity (depending on jasmonic acid) is turned off, the formation of defence compounds that render the kamikaze strategy of the victim efficient is suppressed. At the same time, the neighbouring cells are overwhelmed by false alarm, such that they already start killing themselves before the fungus has even arrived. This sophisticated strategy was unveiled by Dr. Junning Ma who did his PhD with us funded by the Chinese Scholarship Council and has now been published in the Journal of Experimental Botany.

225. Ma J, Morel JB, Riemann M, Jacob S, Nick P. Pyriculol-mediated defence potentiation in rice: a non-pathogenic secondary metabolite enhances host immunity against Magnaporthe oryzae. J Exp Bot, 10.1093/jxb/erag061 - pdf

Press Release of the KIT

New Project in the Field of Vertical Farming

November 1, our new cooperation project with the Start-up Vertical Farming and the Max-Rubner-Institute, funded by the Federal Institute for Agriculture, will be launched. Running time is three years. A precursor project, funded by the State of Baden-Württemberg tested, in the Botanic Garden of the KIT, a prototype for a Vertical Farm device, where the accumulation of value giving compounds was stimulated by repeated gravity stimulation. In theis context, we discovered that aeroponics (spraying the roots with a nutritious mist) stimulates root growth to an extent never seen before. The new project will now valorise this discovery. Target are cash rhizome crops such as Ginger, Turmeric, or Wasabi. To protect the precious products from infection by pathogens, a new technology will be tested, where the roots are inoculated by root bacteria that had been identified by us previously. These microbes can stimulate plant immunity. This will allow to avoid chemical plant protection, but also circumvent the need for the extreme quarantine standards commonly used in Vertical Farming. This will lower costs considerable and extend the applicability of this new farming method far beyond current use. 

Microtubules and the Dogs of Hell

Cerberus, the three-headed Dog of Hell guards in Greek mythology the realm of dead, Hades. Herkules succeeds in putting the dog on a leash and by this to intrude into the other world. This metaphor seems to work also for plant immunity: during the so-called Hypersensitive Response the infected cell comits harakiri and by this pulls the attacker into death. This cellular suicide is executed by so-called metacaspases, protein degrading enzymes that by name, but not by evolutionary origin, derive from the caspases that do a similar job during the apoptosis of animal cells. But how does the cell prevent that these Dogs of Hell do not start their destructive work in healthy cells? We have addressed this question in cells of grapevine and found out that the central metacaspase 5 is bound to microtubules, a main component of the plant cytoskeleton. When the cell is sensing an attack (we mimic this in the experiment with chemical signals), it actively makes microtubules disappear and by this releases Cerberus from the leash, who, within a few hours, does a thorough job. Using a combination of cell biological and biochemical approaches we demonstrate this novel, hitherto unknown function of microtubules. 

Publication

222. Zhu X, Zhang K, Gong P, Riemann M, Nick P (2025) Unleash the Dogs of Death: Vitis Metacaspase 5, Microtubules, and Hypersensitive Response. Plant Cell Reports, doi 10.1007/s00299-025-03567-x - pdf

EvoDevo of Speciation

"Species" are a central concept of biology and usually understood as unit of propagation. This species concept works neatly for animals, because mating of individuals from different species usually do not work or lead to sterile progeny (a classic example would be the mule). Plants, however, do not choose their mating partner themselves, but use insects for doing so. Moreover, plants can circumvent problems with sexuality by asexual propagation. What does "species" now mean for plants? Dr. Sascha Wetters proposed here a new concept, whereby genes that control shape or geometry of flowers are drivers of speciation. To test this idea, he cracked a hard nut - the genus Sage, with more than 1000 known species, one of the most diverse genera at all. Here, he can show that a duplication of the gene switch GLOBOSA facilitated the colonisation of the New World by larger and less asymmetric flowers that recruited novel pollinators, hummingbirds, leading to the birth of numerous new species. This allows to bridge developmental biology and evolution. This work has now been published.

217. Wetters S, Nick P (2025) B-class gene GLOBOSA – a facilitator for enriched species diversity of Salvia in the New World? Plant Biol, 10.1111/plb.70002 - pdf

EUCOR Project Roots of Resilience

EUCOR, the trinational assocation of Upper-Rhine universities (Karlsruhe, Strasbourg, Freiburg, Colmar-Mulhouse, Basel) launched a call for so-called Seed Money projects. Here, partner KIT-JKIP (Islam Khattab, Peter Nick) together with the University of Basel (Pascale Flury) and the Université Haute-Alsace (Julie Chong) was successful with the project Roots of Resilience. The project tries to render grapevine more resilient against climate-change born novel fungal diseases ("Esca & Co") through improved microbial communities in the rhizosphere. The project is based on results of Kliwiresse, but also previous Upper Rhine Interreg projects, especially Vitifutur and DialogProTec. However, the central reason for the success of the proposal was the cooperation cultivated over four Interreg Upper Rhine networks. The Seed Project in turn will feed into the planned sequel project Robin Root. Planned start is February 2025, running time is two years. more...

Salt Tolerant Sorghum Millet

Climate changes makes sea levels rise making fertile coastal land salty. The Nile delta, Bangladesh, Vietnam, but also the South of Italy are already today confronted with salt stress. Can we find crop plants that are able to thrive on such soils? In the past, we have, initiated by our Syrian colleague Dr. Adnan Kanbar, focused on stress resilience in Sorghum Millet. This ancient crop originates from Sudan and can cope with harsh conditions. In fact, we were able to show that some Sorghum varieties not only can grow under salinity, but accumulate more sugar when confronted with salinity. What happens to this sugar, differs - some Sorghum varieties store it in the shoot, what is interesting for bio-economic use (for instance for the production of bio-ethanol) others store it in their seeds, what supports food security in regions affected by soil salinity. During her PhD our colleague Eman Abuslima from Egypt was able to uncover the reason for the different sugar use: a gene switch for the sugar transporter SWEET13 decides. A very active version of this switch could be identified in the old Syrian landrace Razinieh. By breeding, this switch can now be crossed into other millet varieties, and by means of the molecular knowledge, the promising individuals in the progeny can be recognised already in the seedling stage by a simple PCR. 
 

Publication

216. Abuslima E, Kanbar A, Ismail A, Raorane ML, Eiche E, El-Sharkawy I, Junker BH, Riemann M, Nick P (2025) Salt stress-induced remodeling of sugar transport: a role for promoter alleles of SWEET13. Nature Sci Rep 15, 7580 - pdf

PRESS RELEASE OF KIT

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