Shortened snRNA promoters for efficient CRISPR/Cas-based multiplex genome editing in monocot plants

Dear Editor,CRISPR(clustered regularly interspaced short palindromic repeats)/Cas genome editing is a powerful tool for introducing specific mutations in organisms including plants.The system is composed of a nuclease such as Cas9 or Cas12a and an engineered single-guide RNA(sgRNA)incorporating a target sequence(Li et al.,2019).A Cas9/sgRNA complex recognizes its target site in the genome,resulting in a mutation at that site.

Self-cleaving ribozymes enable the production of guide RNAs from unlimited choices of promoters for CRISPR/Cas9 mediated genome editing

Development of tools for targeted modifications of specific DNA sequences in plants is of great importance to basic plant biology research as well as crop improvement.The ability to cut DNA at specific locations in the genome to generate doublestrand breaks（DSBs）in vivo is a prerequisite for any genome editing efforts.

DeepCBA:A deep learning framework for gene expression prediction in maize based on DNA sequences and chromatin interactions

Chromatin interactions create spatial proximity between distal regulatory elements and target genes in the genome,which has an important impact on gene expression,transcriptional regulation,and phenotypic traits.To date,several methods have been developed for predicting gene expression.However,existing methods do not take into consideration the effect of chromatin interactions on target gene expression,thus potentially reducing the accuracy of gene expression prediction and mining of important regulatory elements.In this study,we developed a highly accurate deep learning-based gene expression prediction model(DeepCBA)based on maize chromatin interaction data.Compared with existing models,DeepCBA exhibits higher accuracy in expression classification and expression value prediction.The average Pearson correlation coefficients(PCCs)for predicting gene expression using gene promoter proximal interactions,proximaldistal interactions,and both proximal and distal interactions were 0.818,0.625,and 0.929,respectively,representing an increase of 0.357,0.16,and 0.469 over the PCCs obtained with traditional methods that use only gene proximal sequences.Some important motifs were identified through DeepCBA;they were enriched in open chromatin regions and expression quantitative trait loci and showed clear tissue specificity.Importantly,experimental results for the maize flowering-related gene ZmRap2.7 and the tillering-related gene ZmTb1 demonstrated the feasibility of DeepCBA for exploration of regulatory elements that affect gene expression.Moreover,promoter editing and verification of two reported genes(ZmCLE7 and ZmVTE4)demonstrated the utility of DeepCBA for the precise design of gene expression and even for future intelligent breeding.DeepCBA is available at http://www.deepcba.com/or http://124.220.197.196/.