Genome editing in cotton is hindered by the species' complex genetic make-up, requiring higher levels of CRISPR-Cas9 components than usual to obtain expected results. Cotton is a heterotetraploid, which makes targeted mutagenesis for this crop's improvement inefficient and time-consuming. To address this problem, scientist Chun-Peng Song of State Key Laboratory of Cotton Biology in China and colleagues utilized transient expression to determine the most efficient expression vector for faster CRISPR-Cas9-mediated genome editing in cotton. 

sgRNA is a component of the CRISPR-Cas9 editing complex and is responsible for the accurate targeting of genes of interest. In the mentioned study, researchers used a U6 promoter, resulting in enhanced sgRNA expression (six to seven times better), and thus, enhanced gene targeting (four to six times better) in cotton. This promoter proves to be effective in enhancing gene editing in cotton. Transient expression also proved to be a beneficial tool to hasten vector optimization in genome editing.

For more information, read the article in Plant Methods.