Transgenic Caenorhabditis elegans harboring large extrachromosomal arrays (several megabases) are relatively easy to generate, but suffer from variable and mosaic expression. Here, we describe a detailed protocol for stable transgene expression by chromosomal integration of arrays at safe-harbor landing sites or at the endogenous unc-119 locus. Our strategy is based on a single DNA-based injection resulting in efficient array integration (20 to 40% of injected animals) in 10 days. Despite the genomic co-integration of Cas9 and sgRNA, the arrays remain stable across generations.

Protein-metabolite interactions (PMIs) are fundamental for several biological processes. Even though PMI studies have increased in recent years, our knowledge is still limited. The screening of PMIs using small molecules as bait will broaden our ability to uncover novel PMIs, setting the basis for establishing their biological relevance. Here, we describe a protocol that allows the identification of multiple protein partners for one ligand. This protocol describes a straightforward methodology that can be adapted to a wide variety of organisms.

Precise expression of transgenes in C. elegans can be used to understand gene regulation, control cells, or as a starting point for genetic screens. Insertion of single-copy transgenes into well-defined safe-harbor locations is useful when a consistent expression levels are required (e.g., to compare expression from different transgenes) or when expression is desired in germ cells. Here, we describe a detailed protocol for inserting single-copy transgenes using Modular Safe-harbor Transgene Insertion (MosTI) and a heat-shock inducible Cas9 expressed from a co-injected plasmid. Inducible Cas9 expression has the advantage of requiring few injections, and many independent single-copy insertions can be generated from a single array line.

Transgenesis in model organisms is an essential tool for determining the function of protein-coding genes and non-coding regulatory regions. In Caenorhabditis elegans, injected DNA can be propagated as multicopy extra-chromosomal arrays, but transgenes in arrays are frequently mosaic, over-expressed in some tissues, and silenced in the germline. Here, we describe methods to insert single-copy transgenes into specific genomic locations (MosSCI) or random locations (miniMos) using Mos1 transposons. Single-copy insertions allow expression at endogenous levels, expression in the germline, and identification of active and repressed regions of the genome.

Understanding the biological background of strigolactone (SL) structural diversity and the SL signaling pathway at molecular level requires quantitative and sensitive tools that precisely determine SL dynamics. Such biosensors may be also very helpful in screening for SL analogs and mimics with defined biological functions. Recently, the genetically encoded, ratiometric sensor StrigoQuant was developed and allowed the quantification of the activity of a wide concentration range of SLs. StrigoQuant can be used for studies on the biosynthesis, function and signal transduction of this hormone class. Here, we provide a comprehensive protocol for establishing the use of StrigoQuant in Arabidopsis protoplasts. We first describe the generation and transformation of the protoplasts with StrigoQuant and detail the application of the synthetic SL analogue GR24. We then show the recording of the luminescence signal and how the obtained data are processed and used to assess/determine SL perception.

Targeted modification of plant genomes is a powerful strategy for investigating and engineering cellular systems, paving the way for the discovery and development of important, novel agricultural traits. Cas9, an RNA-guided DNA endonuclease from the type II adaptive immune CRISPR system of the prokaryote Streptococcus pyogenes, has gained widespread popularity as a genome-editing tool for use in a wide array of cells and organisms, including model and crop plants. Effective genome engineering requires the delivery of the Cas9 protein and guide RNAs into target cells. However, in planta genome modification faces many hurdles, including the difficulty in efficiently delivering genome engineering reagents to the desired tissues. We recently developed a Tobacco rattle virus (TRV)-mediated genome engineering system for Nicotiana benthamiana. Using this platform, genome engineering reagents can be delivered into all plant parts in a simple, efficient manner, facilitating the recovery of progeny plants with the desired genomic modifications, thus bypassing the need for transformation and tissue culture. This platform expands the utility of the CRISPR/Cas9 system for in planta, targeted genome modification. Here, we provide a detailed protocol explaining the methodologies used to develop and implement TRV-mediated genome engineering in N. benthamiana. The protocol described here can be extended to any other plant species susceptible to systemic infection by TRV. However, this approach is not limited to vectors derived from TRV, as other RNA viruses could be used to develop similar delivery platforms.

The use of ontologies has increased rapidly over the past decade and they now provide a key component of most major databases in biology and biomedicine. Consequently, datamining over these databases benefits from considering the specific structure and content of ontologies, and several methods have been developed to use ontologies in datamining applications. Here, we discuss the principles of ontology structure, and datamining methods that rely on ontologies. The impact of these methods in the biological and biomedical sciences has been profound and is likely to increase as more datasets are becoming available using common, shared ontologies.