Quantitative Analysis of Protein‐Protein Interactions by Split Firefly Luciferase Complementation in Plant Protoplasts

Targeted Transcriptional Activation in Plants Using a Potent Dead Cas9-Derived Synthetic Gene Activator

Genetic tools for specific perturbation of endogenous gene expression are highly desirable for interrogation of plant gene functions and improvement of crop traits. Synthetic transcriptional activators derived from the CRISPR/Cas9 system are emerging as powerful new tools for activating the endogenous expression of genes of interest in plants. These synthetic constructs, generated by tethering transcriptional activation domains to a nuclease-dead Cas9 (dCas9), can be directed to the promoters of endogenous target genes by single guide RNAs (sgRNAs) to activate transcription. Here, we provide a detailed protocol for targeted transcriptional activation in plants using a recently developed, highly potent dCas9 gene activator construct referred to as dCas9-TV. This protocol covers selection of sgRNA targets, construction of sgRNA expression cassettes, and screening for an optimal sgRNA using a protoplast-based promoter-luciferase assay. Finally, the dCas9-TV gene activator coupled with the optimal sgRNA is delivered into plants via Agrobacterium-mediated transformation, thereby enabling robust upregulation of target gene expression in transgenic Arabidopsis and rice plants. © 2019 by John Wiley & Sons, Inc.

A Simple Protoplast-Based Method for Screening Potent Artificial miRNA for Maximal Gene Silencing in Arabidopsis

The unpredictability of in planta silencing efficiency of artificial micro RNAs (amiRNAs) has greatly limited the application of the amiRNA technology in basic and applied plant research. This unit describes a simple and robust method called the epitope-tagged protein-based amiRNA (ETPamir) screen for identifying the most effective amiRNA for silencing a particular Arabidopsis gene. After selecting three to four amiRNA candidates designed by the WMD3 web server for the target gene, the silencing efficiencies of the amiRNA candidates can be compared by co-expressing individual amiRNAs with the target mRNA encoding an epitope-tagged target protein in Arabidopsis mesophyll protoplasts. By monitoring target protein levels through immunoblotting with commercial "anti-tag" antibodies, the most potent amiRNA can be easily identified as the one with minimal target protein accumulation. This empirical method bypasses the complexity of amiRNA silencing mechanisms and the scarcity of plant specific antibodies, and can be applied to a broad range of plant species. © 2017 by John Wiley & Sons, Inc.

Gene functional analysis using protoplast transient assays

The protoplast transient assay system has been widely used for rapid functional analyses of genes using cellular and biochemical approaches. This system has been increasingly employed for functional genetic studies using double-stranded (ds) RNA interference (RNAi). Here, we describe a modified procedure for the isolation of protoplasts from leaf mesophyll cells of 14-day-old Arabidopsis thaliana. This modification significantly simplifies and speeds up functional studies without compromising the yield and the viability of protoplasts. We also present the procedure for the isolation and transfection of protoplasts from mesophyll cells of an emerging model grass species, Brachypodium distachyon. Further, we detail procedures for RNAi-based functional studies of genes using transient expression of in vitro synthesized dsRNA in protoplasts.