Plant Science

The quantification of plant hormones and related gene expression is essential to improve the understanding of the molecular regulation of plant growth and development. However, plant hormone quantification is still challenging due to extremely low endogenous levels and high chemical diversity. In this study, we present a convenient extraction protocol that enables the simultaneous extraction of both phytohormones and RNA from the same sample in a small quantity (approximately 10 mg). Using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS), this protocol provides a method to quantify 13 phytohormones and their derivatives from four classes (cytokinin, auxin, abscisic acid, and gibberellin) at the speed of 14 min per sample.

Plant hormones regulate many physiological processes that largely influence growth, differentiation, and development. Contents of phytohormones were analyzed using a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) system. This protocol describes a detailed procedure to extract and quantify indole-3-acetic acid (IAA) and gibberellin acid (GA) in rice (Oryza sativa) tissues using high-performance liquid chromatography (HPLC)-based method.

Many rhizobacteria isolated from plant rhizosphere produce various phytohormones in the form of secondary metabolites, the most common of which is Indole-3-acetic acid (IAA). Here, we detail analytical protocols of IAA detection and quantification, in vitro and in situ, as recently applied to Klebsiella SGM 81, a rhizobacterium isolated from the rhizosphere of Dianthus caryophyllus (a commercially important flower across the globe). Specifically, we describe a detailed protocol for a colorimetric assay using the Salkowski reagent method, which can be used to screen for the presence of Indole compounds. To further detect and quantify IAA, a highly accurate analytical approach of LC-MS/MS is used. To detect the presence of IAA around the root system of Dianthus caryophyllus, in situ staining of plant roots is done using Salkowski reagent.

Homeostasis between the cytoplasmic plant hormone salicylic acid (SA) and its’ inactive, vacuolar storage forms, SA-2-O-β-D-glucoside (SAG) and SA-β-D-Glucose Ester (SGE), regulates the fine-tuning of defense responses to biotrophic pathogens in Arabidopsis thaliana. This protocol describes a simplified, optimized procedure to extract and quantify free SA and total hydrolyzable SA in plant tissues using a classical HPLC-based method.

The Rapid Alkalinization Factor (RALF) is a plant hormone peptide that inhibits proton transport causing alkalinization of the extracellular media. To detect the alkalinization response elicited by RALF peptides in root cells, Arabidopsis seedlings are carefully transferred to a gel containing the pH-sensitive indicator bromocresol purple, treated with the peptide and photographed after 30 min. Herein the protocol is optimized for evaluation of exogenous treatment, described in detail and expected results are presented.

Brassinosteroids (BRs) promote rice lamina inclination. Recently, we showed that OsBUL1 knockout mutant rice (osbul1) is defective in brassinosteroid signaling (Jang et al., 2017). To show that lamina joint inclination of osbul1 is less-sensitive than WT to exogenous brassinolide (BL) treatment in the lamina joint inclination bioassays, we applied the protocol presented below. The protocol focuses on: (1) how to prepare rice samples for the assay, and (2) how to treat BL exogenously. Finally, we have added a result showing lamina inclination between WT and osbul1 in BL solutions of various concentrations.

Abscisic acid (ABA) has been known as a phytohormone of land plants, which is synthesized in response to abiotic stresses and induces various physiological responses, but is also found from eukaryotic algae. Recently, we reported that a unicellular red alga Cyanidioschyzon merolae produced ABA, which prevented cell growth and enhanced salt stress tolerance (Kobayashi et al., 2016). This report describes the detailed method for the extraction and quantification of ABA in the model red alga C. merolae.

This assay analyzes Arabidopsis seed germination in response to gibberellic acid (GA). During seed imbibition, visible physiological changes allow precise determination of germination rate. This protocol utilizes a stereoscopic microscope to improve characterization of seed germination process.

An emerging theme in biology is the importance of cellular signaling dynamics. In addition to monitoring changes in absolute abundance of signaling molecules, many signal transduction pathways are sensitive to changes in temporal properties of signaling components (Purvis and Lahav, 2013). The phytohormone auxin regulates myriad processes in plant development. Many of these require the nuclear auxin signaling pathway, in which degradation of the Aux/IAA repressor proteins allows for transcription of auxin-responsive genes (Korasick et al., 2015). Using a heterologous yeast system, we found that Aux/IAAs exhibit a range of auxin-induced degradation rates when co-expressed in isolation with F-box proteins (Havens et al., 2012). Subsequent studies connecting signaling dynamics to plant growth and development confirmed that Aux/IAAs show similar differences in plants (Guseman et al., 2015; Moss et al., 2015). Here, we describe in detail the use of a heat-shock-inducible fluorescence degradation system to capture Aux/IAA degradation in real time in live plant roots. By employing this method, we were able to obtain high Aux/IAA expression and avoid the dampening long term effects of turnover, feedback and silencing. Degradation was dependent on the presence of an Aux/IAA degron and rates increased in response to exogenous auxin.

Measurement of auxin transport capacity provides quantitative data on the physiological machinery involved in auxin transport within plants. This technique is easy to perform and gives quick results. Radiolabelled auxin (indole-3-acetic-acid) is fed into the roots of Medicago truncatula via an agar block. The resulting radioactivity from radiolabelled auxin uptake in the roots is measured with a liquid scintillation counter. Here, we describe the measurement of auxin transport capacity around the nodulation susceptible zone in young seedling roots of M. truncatula in response to rhizobia inoculation. Similar assays could be adapted in other plant species and to answer other biological questions.