Oil accumulation in leaves driven by a native promoter-gene fusion created using CRISPR/Cas9 mediated genomic deletion

Achieving gain-of-function phenotypes without inserting foreign DNA is an important challenge for plant biotechnologists. Here we show that a gene can be brought under the control of a promoter from an upstream gene by deleting the intervening genomic sequence using dual-guide CRISPR/Cas9. We fuse the promoter of a non-essential photosynthesis-related gene to DIACYLGLYCEROL ACYLTRANSFERASE 2 (DGAT2) to drive oil biosynthesis in leaves of a lipase deficient sugar-dependent 1 mutant. DGAT2 expression is enhanced more than twenty-fold and the triacylglycerol content increases by around thirty-fold. This strategy offers a transgene-free route to engineering gain-of-function traits such as high lipid forage to increase the productivity and sustainability of ruminant farming.