The ideal crop plant is tasty and high yielding while being disease and pest resistant. But if the genes involved are far apart on a chromosome, some of these positive traits may be lost during reproduction. To ensure that positive traits can be passed on together, researchers at the Karlsruhe Institute of Technology (KIT) used CRISPR/Cas molecular scissors to reverse and thereby genetically disable nine-tenths of a chromosome. Traits encoded for this part of the chromosome become “invisible” to genetic exchange and can thus be passed on as they are. The researchers reported their findings in Natural plants.
The targeted editing, insertion or deletion of genes in plants is possible with the CRISPR/Cas molecular scissors. (CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats.) This method can be used to make plants more resistant to pests, diseases or environmental influences. “In recent years, we have been able for the first time to use CRISPR/Cas not only to edit genes, but also to modify the structure of chromosomes”, explains Professor Holger Puchta, who for 30 years has been researching applications for scissors. genes with his team from the KIT Botanical Institute. “Genes are arranged linearly along chromosomes. By altering their sequence, we were able to show how desirable traits in plants can be separated from those that are not.”
Now researchers have been able to prevent the genetic exchange that is normally part of the hereditary process but can break the links between traits. “We can close a chromosome almost completely, making it invisible, so all the traits of that chromosome can be passed on in one bundle,” Puchta says. Until now, if a plant’s traits were to be passed down together, the genes for those traits had to be close together on the same chromosome. If these genes are further apart on a chromosome, they are usually separated during inheritance, so a beneficial trait may be lost during the breeding process.
Learning from nature: chromosomal engineering prevents genetic exchange
In their research, scientists have followed the example of nature. “These reversals, or inversions – a kind of genetic invisibility – also occur frequently on a smaller scale in wild and cultivated plants. We learned from nature and applied and extended our knowledge of the natural process,” says Puchta. .
Together with Professor Andreas Houben of the Leibniz Institute for Plant Genetics and Crop Research (IPK), Puchta and his team reversed nine-tenths of a chromosome in the model organism Arabidopsis thaliana (thale watercress) . It is only at the ends of the chromosome that the genes have retained their original sequence. “With these fragments, the chromosome can be passed on to the next generation just like other chromosomes and is not completely lost,” says Puchta.
Enable future cultivation of more efficient and robust crop plants
To effectively breed crops, it is important to combine as many favorable traits as possible in a single plant. “Of course, plant breeders want their products to taste good, contain as many vitamins as possible and also be disease resistant. With our method, we can facilitate this in the future,” says Puchta.