Scientists continuously try to improve the efficiency of CRISPR-Cas9 system by focusing on the transcriptional level. By contrast, researcher Jian-Kang Zhu from Chinese Academy of Sciences and colleagues try improving the system by focusing on the post-transcriptional level. They induced the expression of p19 protein and silence the AGO1 protein related in RNA interference. They found improved expression of CRISPR-Cas9 components and different symptom severity in the tested plants.

Higher expression of CRISPR-Cas9 components allows higher gene editing frequency, reducing the cost of producing mutants for screening. Moreover, selection through the naked eye also reduces the cost of selecting mutated plants through other molecular techniques. Overall, the system provides practicality in increasing gene expression and selecting transgene-free CRISPR-Cas9-edited plants in the first and second generations by naked-eye observation of symptom severity. 

For more information, read the article in BMC Genome Biology.