University of Cologne
Every plant is populated by numerous microorganisms. Members in this so-called microbiome are also numerous fungi from the soil. The research group of Prof. Dr. Marcel Bucher from the Cluster of Excellence on Plant Science (CEPLAS) studied the symbiosis with a particular fungus of the root microbiome and its host plant Arabis alpina (Alpine Rock-Cress). The study revealed that a particular fungus from the root microbiome, which was previously unknown, provides its host plant in nutrient-poor soils with phosphorus and thus stimulates its growth.
“The results of this work are important for our understanding of the cooperation between plants and microorganisms that populate the roots“ says Professor Dr. Marcel Bucher. The research team describes the results in the publication "Root-associated fungal microbiota of nonmycorrhizal Arabis alpina and its contribution to plant phosphorus nutrition“, which has been published in the current issue of "Proceedings of the National Academy of Sciences of the USA” (PNAS).
The recent study explains how plants are capable of growing in phosphorus-impoverished soils. The fungus takes on the role of other well-known and specialized fungi that establish a so-called mycorrhizal symbiosis with most plants. However, a symbiosis with these specialized fungi does in fact not exist in Arabis alpina and related species. The central question was therefore whether other fungi can be beneficial for the plant.
In a first step, the fungal microbiome of the plant root was studied by high-throughput sequencing of a short part of the genome that is typical for fungi. From this sequence anaylsis, the research team could draw conclusions on the identity and function of the fungi in the plant’s microbiome. The analysis of biological diversity and the evolutionary relationships between different fungi showed that the diversity within the soil decreases, from the outside to the inside. It is particularly high in the unplanted parts of the soil while it decreases in the inner root of the plant. “This signifies that plants function as filters for microorganisms in the soil. They have the ability to select between particular consortia of fungi” Bucher explains. In addition, numerous fungi from the Arabis root were cultivated in the laboratory. “We could examine a previously unknown fungus. This Helotiales fungus frequently occurs in the French Alps under rough conditions and apparently plays an important role in the plant’s survival” says Bucher. It lives within the root, grows into particular root cells and connects the inner with the outer part of the root. Whenever the fungus was part of the microbiome of a plant in phosphorus-impoverished soil, the research team could determine an increased growth and a higher phosphorus-uptake.
In cooperation with CEPLAS-Professor Alga Zuccaro, the research team could show that the genes for carbohydrate-active enzymes are particularly prominent within the fungus‘ genome. “The habitat in the root interior apparently presents the ideal niche for the fungus. It can sustain a mutually beneficial symbiosis with its host plant and live on the products of photosynthesis” Marcel Bucher explains. “Since the impact of climate change for the microbial and plant environment is largely unknown in a global context, the combination of demanding laboratory analysis and outdoor research is all the more important. In this context, CEPLAS makes a valuable contribution” says Bucher.