CRISPR/Cas9-mediated targeted T-DNA integration in rice

Area of Science:

• Plant Molecular Biology
• Genome Editing
• Biotechnology

Background:

• Agrobacterium-mediated T-DNA integration into plant genomes is typically random, leading to unpredictable transgene expression and insertional mutagenesis.
• T-DNA integration often occurs at double-strand DNA breaks, a characteristic that can be exploited for targeted insertion.

Purpose of the Study:

• To adapt the CRISPR/Cas9 system for targeted T-DNA integration in the rice genome.
• To develop a method for precise T-DNA insertion using Agrobacterium and CRISPR/Cas9, overcoming the limitations of random integration.

Main Methods:

• Constructed a T-DNA within a standard Agrobacterium binary vector containing the CRISPR/Cas9 system (SpCas9 and a specific gRNA).
• Designed T-DNA constructs to target the Os01g04020 gene exon in rice, including reporter genes (red fluorescent protein and hygromycin resistance).
• Utilized two vector versions: one with constitutive hptII expression and another with a promoterless hptII for in-frame integration detection.

Main Results:

• Achieved targeted T-DNA insertions at frequencies of 4–5.3% in transgenic callus events.
• Generated high frequencies (50–80%) of targeted indel mutations at the intended site.
• Sequencing confirmed that a significant proportion of insertions (4/5 junctions) involved single-copy, full-length T-DNA at the target locus.

Conclusions:

• Agrobacterium-mediated transformation, when combined with CRISPR/Cas9, can efficiently achieve targeted T-DNA insertions in the rice genome.
• This integrated approach offers a powerful tool for precise genetic modification in rice, improving control over transgene integration.
• The method successfully demonstrated targeted integration, paving the way for more predictable plant genome engineering.