Karlsruhe Institute of Technology: Targeted elimination of individual cell types with gene scissors

With the molecular scissors CRISPR/Cas, genetic information in a plant can be modified to make it more robust against pests, diseases or extreme climatic conditions. Scientists at the Karlsruhe Institute of Technology (KIT) have now further developed this method so that for the first time they are able to eliminate the complete DNA of specific cell types and thus prevent their formation during plant development. This should help to better understand the development processes in plants. The researchers are presenting their results in the journal Nature Communications . (DOI: 10.1038/s41467-022-29130-w )

Molecular scissors make it possible to change the DNA – i.e. the carrier of genetic information – in plants. The CRISPR/Cas method for plants co-developed by Professor Holger Puchta, molecular biologist at the KIT Botanical Institute, has already made it possible to insert, exchange or combine genes in a targeted manner in order to make crops more resistant to diseases and environmental influences. CRISPR (stands for Clustered Regularly Interspaced Short Palindromic Repeats)/Cas is a molecular pair of scissors that recognizes and cuts DNA sequences in a highly specific manner. “We have been researching molecular scissors for plants for 30 years. In the beginning, we used them to change individual genes. Two years ago, for the first time in the world, we succeeded in reshaping entire chromosomes,” says Puchta, who is considered a pioneer of genome editing with molecular scissors and has twice received the renowned Advanced Grant from the European Research Council (ERC) for his research. “Now we have optimized the previous method and reached a completely new level in development with CRISPR-Kill: We can now switch off individual plant cell types and thus prevent the development of very specific plant characteristics.”

Eliminate lateral roots and petals with CRISPR-Kill

In their experiments, the scientists concentrated on the lateral roots and petals of the model plant thale cress (Arabidopsis thaliana). “These are classic examples in biology. Here we know the genetic program and know which cell types are important for the development of these parts of the plant,” says the molecular biologist. After knocking out the specific cell types, the CRISPR-kill plants did not develop petals or lateral roots, while the control plants showed normal growth.

In contrast to other methods in which cells are eliminated using cytotoxins or the use of laser radiation, the CRISPR-Kill method aims to cut specific locations in the genome. A genome consists of a certain number of chromosomes on which the individual genes are arranged in a fixed order. “So far, with CRISPR/Cas, we have targeted exactly one point and made one or two cuts to change a gene or chromosome,” says Puchta. “Now we have reprogrammed the molecular scissors in such a way that they not only cut once in the respective cell type, but also control a sequence that occurs frequently in the genome and is essential for the survival of the cell. So many cuts occur at the same time – so many that the cell can no longer repair them and dies.”

Understand the developmental processes in plants better

With their work, the researchers at KIT contribute to basic research. “By studying what happens when you turn off one cell type or the other, we can learn more about the developmental processes in plants. How does the plant react? How flexible is it in its development? Can we remove parts of plants that are not needed in agriculture, for example?” Puchta looks to the future. In the long term, both food production and pharmaceutical applications could benefit from this technology, for example by specifically preventing the emergence of cells that produce toxins during plant development. The technology could also be used in other multicellular organisms for the targeted modification of tissues. (swiss)

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