Multi-imaging of Cytokinin and Abscisic Acid on the Roots of Rice (Oryza sativa) Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

Plant hormones act as important signaling molecules that regulate responses to abiotic stress as well as plant growth and development. Because their concentrations of hormones control the physiological responses in the target tissue, it is important to know the distributions and concentrations in the tissues. However, it is difficult to determine the hormone concentration on the plant tissue as a result of the limitations of conventional methods. Here, we report the first multi-imaging of two plant hormones, one of cytokinin [i.e., trans-zeatin (tZ)] and abscisic acid (ABA) using a new technology, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) imaging. Protonated signals of tZ (m/z 220.1) and ABA (m/z 265.3) were chosen on longitudinal sections of rice roots for MS imaging. tZ was broadly distributed about 40 mm behind the root apex but was barely detectable at the apex, whereas ABA was mainly detected at the root apex. Multi-imaging using MALDI-TOF-MS enabled the visualization of the localization and quantification of plant hormones. Thus, this tool is applicable to a wide range of plant species growing under various environmental conditions.

Sensors for the quantification, localization and analysis of the dynamics of plant hormones

“…SnRK2 then phosphorylates downstream proteins, including ABA‐responsive element (ABRE)‐binding transcription factors and ion channels. The distribution of ABA has successfully been detected by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) imaging (Shiono et al ., 2017) and transcriptional biosensors (Wu et al ., 2018). Transcriptional biosensors were developed that consisted of synthetic promoters, based on repeats of the ABRE elements, upstream of GFP fused with an endoplasmic reticulum (ER)‐retention signal (erGFP) (Wu et al ., 2018).…”

Recent developments of MALDI MSI application in plant tissues analysis

“…Plant hormones are substances that regulate growth and development of plants. Cytokinin and abscisic acid are the plant hormones that have been visualized so far (Klein et al, 2015;Shiono et al, 2017). However, some of the plant hormones have not been visualized yet.…”

Keeping the shape of plant tissue for visualizing metabolite features in segmentation and correlation analysis of imaging mass spectrometry in Asparagus officinalis

“…Matrix-assisted laser desorption/ionization−imaging mass spectrometry (MALDI−IMS) is a powerful approach for visualizing the localization of metabolites and is used in sections of organisms (Dong et al 2016; Fujimura and Miura 2014; Lee et al 2012; Sarabia et al 2018; Sturtevant et al 2016). Recently, this approach has been applied to identify the localization of specialized metabolites in plants (Enomoto et al 2018; Jarvis et al 2017; Li et al 2014; Shiono et al 2017). One of the major challenges of MALDI−IMS is to keep plant tissue shapes during the preparation of sections.…”