植物科学

Camelina sativa, a Brassicaceae family crop, is used for fodder, human food, and biofuels. Its relatively high resistance to abiotic and biotic stresses, as well as being a climate-resilient oilseed crop, has contributed to its popularity. Camelina's seed yield and oil contents have been improved using various technologies like RNAi and CRISPR/Cas9 genome editing. A stable transformation system for protein localization and other cell autonomous investigations, on the other hand, is tedious and time consuming. This study describes a transient gene expression protocol for Camelina sativa cultivar DH55 leaves using Agrobacterium strain C58C1. The method is suitable for subcellular protein localization and colocalization studies and can be used with both constitutive and chemically induced genes. We report the subcellular localization of the N-terminal ER membrane signal anchor region (1–32 aa) of the At3G28580 gene-encoded protein from Arabidopsis in intact leaves and the expression and localization of other known organelle markers. This method offers a fast and convenient way to study proteins in the commercially important Camelina crop system.

Key features

• This method is based on the approach of Zhang et al. [1] and has been optimized for bioenergy crop Camelina species.

• A constitutive and inducible transient gene expression in the hexaploid species Camelina sativa cultivar DH55.

• Requires only 16–18 days to complete with high efficacy.

Graphical overview

Agrobacterium-mediated transient gene expression optimized for Camelina sativa

Citrus fruits encompass a diverse family, including oranges, mandarins, grapefruits, limes, kumquats, lemons, and others. In citrus, Agrobacterium tumefaciens–mediated genetic transformation of Hongkong kumquat (Fortunella hindsii Swingle) has been widely employed for gene function analysis. However, the perennial nature of woody plants results in the generation of transgenic fruits taking several years. Here, we show the procedures of Agrobacterium-mediated transient transformation and live-cell imaging in kumquat (F. crassifolia Swingle) fruit, using the actin filament marker GFP-Lifeact as an example. Fluorescence detection, western blot analysis, and live-cell imaging with confocal microscopy demonstrate the high transformation efficiency and an extended expression window of this system. Overall, Agrobacterium-mediated transient transformation of kumquat fruits provides a rapid and effective method for studying gene function in fruit, enabling the effective observation of diverse cellular processes in fruit biology.

Biotin is an essential vitamin in plants. However, characterization of biotin deficiency has been limited by embryo lethality in mutants, which can only be rescued by supplementation of biotin. Here, we describe a protocol to characterize biotin deficiency in Arabidopsis thaliana through application of the polyamine cadaverine. Cadaverine induces changes in primary root growth. Protein biotinylation in Arabidopsis seedlings can be quantified through an assay similar to a western blot, in which protein biotinylation is detected by a streptavidin probe. This technique provides a chemical means of inhibiting biotin synthesis, allowing for further characterization of biotin deficiency on a physiological and molecular level.

The experimental identification of protein-protein interactions (PPIs) is critical to understand protein function. Thus, a plethora of sensitive and versatile approaches have been developed to detect PPIs in vitro or in vivo, such as protein pull-down, yeast two-hybrid (Y2H), co-immunoprecipitation (co-IP), and bimolecular fluorescence complementation (BiFC) assays. The recently established split-luciferase complementation (Split-LUC) imaging assay has several advantages compared to other approaches to detect PPIs in planta: it is a relatively simple and fast method to detect PPIs in vivo; the results are quantitative, with high sensitivity and low background; it measures dynamic PPIs in real-time; and it requires limited experimental materials and instrumentation. In this assay, the amino-terminal and carboxyl-terminal halves of the luciferase enzyme are fused to two proteins of interest (POIs), respectively; the luciferase protein is reconstituted when two POIs interact with each other, giving rise to a measurable activity. Here, we describe a protocol for the Split-LUC imaging assay using a pair of modified gateway-compatible vectors upon Agrobacterium-mediated transient expression in Nicotiana benthamiana. With this setup, we have successfully confirmed a series of interactions among virus-plant proteins, virus-virus proteins, plant-plant proteins, or bacteria-plant proteins in N. benthamiana.

Ralstonia solanacearum is a devastating soil-borne bacterial pathogen that causes disease in multiple host plants worldwide. Typical assays to measure virulence of R. solanacearum in laboratory conditions rely on soil-drenching inoculation followed by observation and scoring of disease symptoms. Here, we describe a novel inoculation protocol to analyze the replication of R. solanacearum upon infiltration into the leaves of Nicotiana benthamiana, in which gene expression has been altered using Agrobacterium tumefaciens. The protocol includes five major steps: 1) growth of N. benthamiana plants; 2) infiltration of A. tumefaciens; 3) R. solanacearum inoculation; 4) sample collection and bacterial quantitation; 5) data analysis and representation. The transient gene expression or gene silencing prior to R. solanacearum inoculation provides a straightforward way to perform genetic analysis of plant functions involved in the interaction between pathogen and host, using the appropriate combination of A. tumefaciens and R. solanacearum strains, with high sensitivity and accuracy provided by the quantitation of bacterial numbers in plant tissues.

Chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) or high-throughput sequencing (ChIP-seq) has become the gold standard for the identification of binding sites of DNA binding proteins and the localization of histone modification on a locus-specific or genome-wide scale, respectively. ChIP experiments can be divided into seven critical steps: (A) sample collection, (B) crosslinking of proteins to DNA, (C) nuclear extraction, (D) chromatin isolation and fragmentation by sonication, (E) immunoprecipitation of histone marks by appropriate antibodies, (F) DNA recovery, and (G) identification of precipitated protein-associated DNA by qPCR or high-throughput sequencing. Here, we describe a time-efficient protocol that can be used for ChIP-qPCR experiments to study the localization of histone modifications in young inflorescences of the model plants Arabidopsis thaliana.

Ratiometric reporters are tools to dynamically measure the relative abundance of a protein of interest. In these systems, a target protein fused to a fluorescent or bioluminescent reporter is expressed with fixed stoichiometry to a reference protein fused to a second reporter. Both fusion proteins are encoded on a single transcript but are separated during translation by a 2A “self-cleaving” peptide. This approach enables changes in the relative abundance of a target protein to be detected sensitively, reducing variability in expression of the ratiometric reporter transgene that may occur across different tissues or transformation events. We recently developed a set of Gateway-compatible plant transformation vectors termed pRATIO that combine a variety of promoters, fluorescent and bioluminescent reporters, and 2A peptides derived from foot-and-mouth disease virus. Here, we describe in detail how to use the dual-fluorescent ratiometric reporter pRATIO3212 to examine the relative abundance of a target protein after transient expression in Nicotiana benthamiana leaves. For this example, we analyze degradation of the SUPPRESSOR OF MAX2 1 (SMAX1) protein from Arabidopsis thaliana in response to treatments with karrikins and rac-GR24. This protocol provides a simple, rapid, and readily scalable method for in vivo analysis of relative protein abundance in Agrobacterium-infiltrated Nicotiana leaf tissues.

Phylogenetics is an important area of evolutionary biology that helps to understand the origin and divergence of genes, genomes and species. Building meaningful phylogenetic trees is needed for the accurate reconstruction of the past. To achieve a correct phylogenetic understanding of genes or proteins, reliable and robust methods are needed to construct meaningful trees. With the rapidly increasing availability of genome and transcriptome sequencing data, there is a need for efficient and accurate methodologies for ancestral state reconstruction. Currently available methods are mostly specific for certain gene families, and require substantial adaptation for their application to other gene families. Hence, a generalized framework is essential to utilize large transcriptome resources such as OneKP and MMETSP. Here, we have developed a flexible yet efficient method, based on core strengths such as emphasis on being inclusive in homolog selection, and defining orthologs based on multi-layered inferences. We illustrate how specific steps can be modified to fit the needs of any protein family under consideration. We also demonstrate the success of this protocol by studying and testing the orthologs in various gene families. Taken together, we present a protocol for reconstructing the ancestral states of various domains and proteins across multiple kingdoms of eukaryotes, using thousands of transcriptomes.

Post-translational modifications play important roles in controlling protein function and can lead to altered protein stability. Protein stability can be determined after treatment with the protein synthesis inhibitor Cycloheximide. Cycloheximide is a translational inhibitor that inhibits protein synthesis via cytoplasmic ribosomes. Here we describe how to measure the stability of MYC2 in the context of regulation by FERONIA receptor kinase. First, we describe how to measure MYC2 stability in wild-type and feronia mutant; then we describe similar assays in transgenic plants expressing MYC2-FLAG and MYC2^A12-FLAG (12 FERONIA phosphorylation sites are mutated to Alanine and the mutant protein is stabilized). MYC2 can be induced by mechanical touch, which can be a confounding factor in protein level measurement. In this protocol, we take that into consideration and try to achieve more accurate measurement.

Laccases are found in cell walls of plants in very low amounts. This protocol provides an efficient method to purify laccases from rice stems. The method involves three steps: 1) Isolation of total protein from rice stems using buffers with high salt concentration to extract protein from cell walls; 2) Purification of laccases using concanavalin-A beads; and, 3) In-gel staining of laccases with 4-hydroxyindole. Concanavalin-A specifically binds to internal or non-reducing terminal α-D-mannosyl and α-D-glucosyl groups found in glycoproteins and glycolipids. Laccases being glycoproteins binds to concanavalin-A during purification process and eluted with mannose.