Targeted genome editing in tetraploid potato through transient TALEN expression by Agrobacterium infection

Genome editing using site-specific nucleases, such as transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeat-CRISPR-associated protein 9 (CRISPR-Cas9), is a powerful technology for crop breeding. For plant genome editing, the genome-editing reagents are usually expressed in plant cells from stably integrated transgenes within the genome. This requires crossing processes to remove foreign nucleotides from the genome to generate null segregants. However, in highly heterozygous plants such as potato, the progeny lines have different agronomic traits from the parent cultivar and do not necessarily become elite lines. Agrobacteria can transfer exogenous genes on T-DNA into plant cells. This has been used both to transform plants stably and to express the genes transiently in plant cells. Here, we infected potato, with Agrobacterium tumefaciens harboring TALEN-expression vector targeting sterol side chain reductase 2 (SSR2) gene and regenerated shoots without selection. We obtained regenerated lines with disrupted-SSR2 gene and without transgene of the TALEN gene, revealing that their disruption should be caused by transient gene expression. The strategy using transient gene expression by Agrobacterium that we call Agrobacterial mutagenesis, developed here should accelerate the use of genome-editing technology to modify heterozygous plant genomes.

Keywords: TALEN; genome editing; potato; steroidal glycoalkaloids; transient gene expression.