Breakthrough in plant breeding: Grafting and mobile CRISPR for genome editing in plants

A ground-breaking twist to the CRISPR tool – aka "genetic scissors" – is being put to use to edit plant genomes by scientists from the Max Planck Institute of Molecular Plant Physiology, signaling a methodology change. The discovery, recently published in the journal Nature Biotechnology, could simplify and speed up the development of novel, genetically stable commercial crop varieties by combining grafting with a "mobile" CRISPR tool.

An unmodified shoot is grafted onto roots that contain a mobile CRISPR/Cas9, which allows the genetic scissor to move from the root into the shoot. There it edits the plant DNA but leaves no trace of itself in the next generation of plants. This breakthrough will save time, money and circumvent current limitations in plant breeding and contribute to sustainable food solutions across multiple crops.

The research group identified the so-called tRNA-like sequences (TLS) that act as signals for the long-distance movement of RNAs within plants. The recent breakthrough came by combining this discovery with the CRISPR/Cas9 genome editing system. When adding such a TLS to the CRISPR/Cas9 sequences, plants produce "mobile" versions of CRISPR/Cas9 RNA. A transgene-free, unmodified shoot is then grafted onto the roots of plants containing the mobile CRISPR/Cas9 RNA, which then moves from the root into the shoot, and eventually on into the flowers that produce the seeds.

"The magic happens in the flowers," explains Dr. Friedrich Kragler. "The CRISPR/Cas9 RNA moves in and is converted into the corresponding protein, which is the actual 'genetic scissors.' It edits the plant DNA in the flowers. But the CRISPR/Cas9 system itself is not integrated in the DNA. So, the seeds that then develop from these flowers carry only the desired editing. There is no trace of the CRISPR/Cas9 system in the next generation of plants and it works with a surprisingly high efficiency."

Image source: RTDS Association.