U6 promoters in Ulva prolifera enable dual small-RNA/mRNA transcription and vector-based CRISPR-Cas9 genome editing

Three identical-sequence UpU6 (U6 snRNA) promoters from Ulva prolifera enable dual small-RNA and protein-coding transcription and support vector-based CRISPR-Cas9 editing.

• Why it matters: Endogenous Pol III promoters are needed to transcribe sgRNAs for vector-based CRISPR-Cas9 in Ulva prolifera, where such promoter tools were lacking.
• What they did: UpU6 promoters were identified, cloned, and tested for reporter activity in U. prolifera and in Agrobacterium, then used to drive CRISPR-Cas9 targeting of the APT gene.
• The result: All three UpU6 promoters produced mutant strains with a 92.3% mutation-positive fraction (48/52) and an average editing frequency of 3.26 x 10-; mutants showed 45.5% base substitutions and 18.2% MULE insertions.