Thursday, August 4, 2022

How plants regulate their sugar balance

Work in the laboratory begins with these tiny Arabidopsis seedlings.
Credit: RUB, Klaus Hagemann

The function of the regulator protein SPL7 in nutrient absorption from the soil was already known. Now it turns out that this protein also plays a role in a completely different context.

As important nutrients, metals, such as copper, convey the functions of many proteins. If this element is in short supply, plants can increase its absorption and switch to copper-independent metabolic pathways. The decisive factor for this is the protein Squamosa Promoter-Binding Protein-Like 7, or SPL7 for short. It belongs to the group of proteins that can regulate which genes are increasingly read and which proteins are increasingly produced. As researchers at the Ruhr University Bochum (RUB) have now found, SPL7 is also essential for energy metabolism.

A team led by Prof. Dr. Ute Krämer from the Chair of Molecular Genetics and Physiology of Plants at the RUB together with colleagues from the Max Planck Institute for Plant Breeding Research in Cologne and for Molecular Plant Physiology in Potsdam in the journal "The Plant Cell".

In photosynthesis, plants produce sugar from carbon dioxide and water using light energy alone. This results in high-energy substances that are the basis of all life on earth. "The improved understanding of how plants control their sugar balance in this study can be useful for the development of new plant-based biotechnological processes," says Ute Krämer. “The findings could also help to increase agricultural yields on copper deficiency soils."

Blind for your own energy status

The Bochum team examined mutants of the model plant Arabidopsis, which cannot produce the protein SPL7. The scientists found that these mutants did not utilize sugar, but enriched it in their tissues. Although they had a lot of sugar, i.e. a lot of energy, they hardly grew. "We suspect that mutants without SPL7 are impaired in recognizing their high energy status or translating it into corresponding growth reactions," concludes Krämer.

Possibly unknown signaling pathways involved

This would mean that SPL7 has a regulatory function in the energy metabolism of plants - in addition to switching on the copper deficiency response. This newly discovered regulatory compound reflects that crucial protein functions in energy metabolism are copper-dependent - both in the photosynthesis of land plants and in breathing. The best studied vegetable sugar signaling pathways worked normally in the SPL7 mutants. The research team therefore assumes that previously unknown signaling pathways could be involved.

In further work, the team would like to research how SPL7 enables plants to use sugar. The first step for this has already been done with the current work. The research team identified all genes whose activity is controlled directly by SPL7. In the future, the working group now wants to find out how some of these genes enable sugar to be used.

The work was funded by the German Research Foundation (Kr1967 / 15-1, Kr1967 / 3-3, Research Training Group 2341 MiCon), the European Commission (ERC-AdG LEAP-EXTREME, Grantnummer788380) and the Wilhelm and Günter Esser Foundation.

Source/Credit: Ruhr University Bochum