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Formation of the Toxic Alkaloid Gramine in Barley Decoded: Publication in "Science"

Formation of the Toxic Alkaloid Gramine in Barley Decoded: Publication in "Science"

With the help of the model plant Nicotiana benthamiana, the metabolic pathway of the toxic alkaloid gramine in barley was elucidated [Photo: Jakob Franke]

Genetic basis of gramine formation revealed

The toxic alkaloid gramine in barley(Hordeum vulgare) is important for defence against insects and pathogens, but makes the grass less palatable or toxic to ruminants. However, in order to be able to control and utilise this interesting biological function in plant breeding, the metabolic pathway of gramine gramine first had to be elucidated – which has now been achieved by a research team from the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) and Leibniz University Hannover (LUH) has now succeeded in doing: a team led by Dr. John D'Auria, head of the IPK Metabolic Diversity working group, and Prof Dr Jakob Franke, head of the Research Group Biochemistry of Plant Specialised Metabolites discovered the genetic basis of gramine biosynthesis.

However, before the publication in the journal Science entitled "Biosynthesis of the allelopathic alkaloid gramine in barley by a cryptic oxidative rearrangement" was published, several steps were important:

Discovery of the crucial enzyme during a bachelor's thesis at the Institute of Botany: AMI synthase (AMIS)

The original discovery of the newly found enzyme AMIS can be traced back to the bachelor's thesis in the Biology degree programme by Johanna Wolf, who is also one of the co-authors. As part of her bachelor's thesis, Mrs Wolf was the first to show that AMIS is responsible for the missing step in the formation of gramine.

As Prof Dr Jakob Franke, head of the working group in Hanover, emphasises: "The entire publication is therefore based on the results of this bachelor thesis. This shows that also final theses can also be central building blocks for cutting-edge research at our faculty."

Important success factors: teamwork and access to research infrastructure

As Jakob Franke points out, it was crucial in the field of protein biochemistry to be able to draw on the expertise of Prof. Dr Witte's Central Nucleotide Metabolism working group for protein biochemistry when characterising AMIS. This cross-institutional collaboration between the Institute of Botany and the Institute of Plant Nutrition, facilitated by their close proximity, was therefore a key success factor. In addition, the generation of the experimental data was based on the shared use of major instrumentation within the faculty, in particular the mass spectrometry systems from the Witte working group.

This type of collaboration with shared use of equipment at the Faculty of Natural Sciences is currently being expanded and will therefore become even easier in the future.

Using the now known metabolic pathway of gramine, the researchers were also able to produce the alkaloid biotechnologically in other organisms - in yeast and in model plants such as Nicotiana benthamiana and Arabidopsis thaliana. Baker's yeast is a very popular model system for biotechnology, which the researchers used to show that the knowledge gained can also be used to produce gramine in other organisms outside of plants. In the future, this will enable the biotechnological production of novel gramine-derived alkaloids. On the other hand, gramine production could be prevented by genome editing in a barley variety.