Healthier beer? For the first time, scientists have modified hop with modern CRISPR technology
More medical substances and bitter acids in hop – that is the aim, the scientists from the Biology Centre of the Czech Academy of Sciences (BC CAS) would like to achieve. They reported the first successful modification of hop using the latest CRISPR genetic technology, which allows very precise targeting of a selected gene. As a first success, the technique was tested on a gene influencing the production of leaf pigments. Now the scientists continue working on genes that affect the production of substances important in the brewing or pharmaceutical industries. The established technology could thus help to breed a better and more beneficial hop for the future generations.
From the dawn of agriculture, people were using the best plants or seeds for further planting. Gradually, they began to cross the best varieties intentionally, in order to combine their best features. But this is a relatively tedious and not always successful process. As modern plant breeders were not satisfied with the qualities that plants already possessed, they started trying to improve plants quality by making changes (mutations) in the responsible genes – using techniques such as radiation or chemical mutagens. "Today, over 3,000 varieties bred by this way are registered and used, such as the Diamant (Diamond) barley, the Vanda strawberry resistant to gray mold, the James Grieve Double Red apple, or Bor - a radiation hop variety," explains Tomáš Kocábek, a researcher at the Institute of Plant Molecular Biology, BC CAS, who investigates genetic modifications of hops. However, this type of breeding reminds blind shooting: mutations arise randomly in all genes and make the selection of both, viable and improved variety, extremely difficult.
Therefore, with the development of molecular techniques, scientists have been exploring not only functions of particular genes, they have also been trying to find a technique that would enable the precise changes in a specific gene. In 2012, the bacterial "immune" system CRISPR/Cas was shown to offer such a possibility. Today, the list of plants genetically engineered by this technology is constantly growing, ranging from model plants to economically usable crops as tomatoes, wheat or fruit trees. "However, hop has been missing from the list so far," adds Dr. Kocábek. and it was exactly the hop plants (Humulus lupulus L.), that scientists from the Institute of Molecular Plant Biology, BC CAS successfully modified using the CRISPR/Cas technology, and reported in the international scientific journal Plant Physiology and Biochemistry in January 2021. As their first target, they chose a model gene responsible for a key enzyme involved leaf pigments - its switch-off is immediately visible on the plant.
Common hop plant (left) and experimental plant with modified gene (right). Photo: Tomáš Kocábek, BC CAS
The leaves of the experimental plants turned completely white or mosaic green-white, moreover the experimental success and appropriate gene targeting was confirmed by molecular analyses. "I am pleased that we have been able to establish this methodology for hop, where it is also a bit complicated by the fact that it is a vegetatively propagated crop," says Praveen Awasthi, a postdoc from the Institute of Molecular Plant Biology, BC CAS, and the lead author of the study, who has previously used the CRISPR technique for banana tree. As a next step, the team will focus on genes responsible for the production of bitter acids, important in brewing industry, or prenylated flavonoids, which can act – among other things – against cancer, bacterial infection and inflammation.
"CRISPR is a completely universal system for everything alive, from microorganisms to human cells, and will certainly bring a lot of interesting results in the future, since it enables to target precisely specific genes without interfering with other parts of the genome," explains Dr. Awasthi. This method also provides undeniable advantage, because – unlike in GMOs – the foreign genes don´t have to be introduced into the “improved” organism. Unfortunatelly, since the European Court of Justice ruled in 2018 that organisms treated with CRISPR techniques are genetically modified organisms (GMO), restrictive regulation virtually prohibits these targeted modifications to the plant genome in the EU. In 2019, the Biology Centre CAS, joined the initiative of European scientists appealing to European bodies to modify legal regulations to allow the usage of this method.
Praveen Awasthi's research was supported by the PPLZ program of the CAS, by the grants CZ.02.2.69 / 0.0 / 0.0 / 16_027 / 0008357 (MEMOBIC), 19-19629S (GAČR) and from the institutional grant 240/9206.
Awasthi, P., Kocábek, T., Mishra, Sukumari Nath, V., Shrestha, A.,Matoušek, J. (2021). Establishment of CRISPR/Cas9 mediated targeted mutagenesis in hop (Humulus lupulus). Plant Physiology and Biochemistry, 160, 1-7. https://doi.org/10.1016/j.plaphy.2021.01.006.