Fig. 1.

Engineering type I-E Cascade complex formation in Zea mays. a Native type I-E CRISPR-Cas locus from S. thermophilus DGCC7710. CRISPR repeats are indicated with a black diamond and the spacer region is in blue. CasE cleaves the primary CRISPR RNA (crRNA) transcript after the hairpin in the CRISPR repeat yielding the mature crRNA depicted. The Cascade complex guided by the crRNA in the vicinity of a 5′ PAM recognizes a double stranded DNA target as illustrated. b Zea mays optimized Cascade and crRNA expression constructs resulting in Cascade complex formation and gene activation. Zm Zea mays, UBI ubiquitin, NLS nuclear localization signal, PinII potato proteinase inhibitor terminator, CBF1 sequence encoding C-terminal acidic transcriptional activation domain from Arabidopsis cold binding factor 1