Plant Science

For obtaining insights into gene networks during plant reproductive development, having transcriptomes of specific cells from developmental stages as starting points is very useful. During development, there is a balance between cell proliferation and differentiation, and many cell and tissue types are formed. While there is a wealth of transcriptome data available, it is mostly at the organ level and not at specific cell or tissue type level. Therefore, methods to isolate specific cell and tissue types are needed. One method is fluorescent activated cell sorting (FACS), but it has limitations such as requiring marker lines and protoplasting. Recently, single-cell/nuclei isolation methods have been developed; however, a minimum amount of genetic information (marker genes) is needed to annotate/predict the resulting cell clusters in these experiments. Another technique that has been known for some time is laser-assisted microdissection (LAM), where specific cells are microdissected and collected using a laser mounted on a microscope platform. This technique has advantages over the others because no fluorescent marker lines must be made, no marker genes must be known, and no protoplasting must be done. The LAM technique consists in tissue fixation, tissue embedding and sectioning using a microtome, microdissection and collection of the cells of interest on the microscope, and finally RNA extraction, library preparation, and RNA sequencing. In this protocol, we implement the use of normal slides instead of the membrane slides commonly used for LAM. We applied this protocol to obtain the transcriptomes of specific tissues during the development of the gynoecium of Arabidopsis.

Steady-state mRNA levels are determined by both the rates of transcription and degradation. Regulation of mRNA stability and/or degradation are key factors that can significantly affect mRNA levels and its biological functions. mRNA stability can be measured indirectly after transcription inhibition. This protocol described a rapid and sensitive method of mRNA stability measurement through quantitative reverse transcription PCR (RT-qPCR) after inhibition of RNA transcription by cordycepin in Arabidopsis seedlings.

Perception of pathogen-associated molecular patterns (PAMPs) often triggers various innate immune responses in plants. The transcriptional changes of defense-related genes are often used as a marker to assay PAMP-triggered plant immune response. Here we described a protocol to monitor the relative expression level of marker genes in Nicotiana benthamiana upon treatment with PAMPs. The procedure includes leaf treatment using PAMPs, total RNA isolation, cDNA synthesis, quantitative real-time PCR and data analysis. This protocol is applicable to monitor marker gene expression triggered by different PAMPs in N. benthamiana.

Production of functional eukaryotic RNA is a very elaborate process that involves a complex interplay between transcription and various RNA processing activities, including splicing, 5’ capping, and 3’ cleavage and polyadenylation (Bentley, 2014). Accurate mapping of RNA ends provides a valuable tool to assess transcriptional and post-transcriptional events giving rise to different gene transcripts. The abundance of such transcripts most likely depends on exogenous and developmental cues, or mutations. In the reference plant Arabidopsis, perturbation of the HUA-PEP post-transcriptional regulatory factors (Rodríguez-Cazorla et al., 2015) leads to the accumulation of aberrant transcripts of the key floral homeotic gene AGAMOUS (AG) (Yanofsky et al., 1990) that retain intronic sequence. It was determined by 3’ RACE reactions that such erroneous transcripts correspond to premature processing and polyadenylation events taking place at the AG intron region. Here we describe a protocol that is suitable for analysis of relatively abundant transcripts and also for detecting aberrant RNA species that are likely prone to rapid turnover. Likewise, the method, here adapted to Arabidopsis reproductive tissues, can be applied to characterize RNA species from other organs (leaf, root) and/or other plant species. We provide a detailed protocol of our 3’ RACE procedure comprising four major parts: Total RNA extraction, RNA amount determination and quality control, the RACE procedure itself, and isolation of the resulting RACE products for cloning and sequencing.

Post-transcriptional processing is critical for RNA biogenesis, in which conventional functional RNA transcripts are generated, such as messenger RNAs (mRNAs), transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs) for translation as well as emerging non-coding RNAs with known or unknown regulatory functions. To determine the precise termini of an RNA molecule during or after processing, the primer extension and Rapid Amplification of cDNA Ends (RACE) methods have been routinely utilized for the precise mapping of 5’ or 3’ ends. Different from these assays, which are designed to detect only one end of a specific target RNA at a time, circular Reverse Transcription-Polymerase Chain Reaction (cRT-PCR) is able to simultaneously determine both the 5’ and 3’ ends of the target RNA. In Arabidopsis thaliana, cRT-PCR has been wildly applied to identify both the 5’ and 3’ extremities of the ribosomal RNA precursors, or to assess the length or post-transcriptional extensions at the 3’ end of a matured mRNA. In this protocol, we summarize and present a detailed procedure of the cRT-PCR assay in Arabidopsis thaliana, which is also successfully used in our previously published work (Hang et al., 2014).

Virus induced gene silencing (VIGS) is one of the most potent reverse genetics technologies for gene functional characterisation. This method exploits a dsRNA-mediated antiviral defence mechanism in plants. Using this method allows researchers to generate rapid phenotypic data in a relatively rapid time frame as compared to the generation of stable transformants. Here we describe a simple method for silencing a target gene in barley seedling leaves using vectors based on the Barley Stripe Mosaic Virus (BSMV).

This is a protocol to produce stable silencing efficacy and efficiency for VIGS using CymMV as a silencing vector for floral functional genomics in Phalaenopsis orchids. This protocol is established based on a method created by Lu et al. (2007), and then modified by Hsieh et al. (2013a; 2013b), Lu et al. (2012) successfully engineered a cloning vector (pCymMV-Gateway) in that the target gene fragment is simple to insert and can be manipulated with high efficiency. The silencing vector is inoculated into plants by Agro-inoculation by using Agrobacterium tumefaciens (A. tumefaciens) strain EHA105. Agro-infiltration of leaves for use in VIGS study of orchid flowers is a time saver and produces less damage to flower buds.

Virus-induced gene silencing (VIGS) is a powerful method to study gene function in plants. Tobacco rattle virus (TRV)-based VIGS vector is the most efficient VIGS vector so far. This method was originally developed by the Dinesh-Kumar's group (Liu et al., 2002) . Here, we describe a rapid and high efficient TRV-based VIGS method for knocking down genes in Nicotiana benthamiana. For TRV-based VIGS, Agrobacterium culture containing pTRV1 and Agrobacterium culture containing pTRV2 with plant target gene fragment are mixed and infiltrated into the lower leaves of plant. After 2-3 weeks post infiltration, plant target gene will be silenced.