Principles and Practice of ABA Analysis - Abscisic Acid: Metabolism, Transport and Signaling - page 429

fragmentation patterns. LC-MS/MS has become the most powerful tool in ABA
analysis because ABA can be analyzed directly without derivatization, which is
needed by the GC-MS or GC-MS/MS. In addition, the metabolomics potential of
LC-MS/MS in simultaneous analysis of ABA-related conjugates and metabolites,
multi-phytohormonal profiles is very promising. However, the high cost of instru-
ments and the consumption of stable isotope-labeled internal standards also hinder
its wider application (Fu et al. 2011 ). Additionally, although the amount of plant
material needed per sample has been greatly decreased for LC-MS/MS, sensitivity
improvement for future methods to ultra-high or single-cell level is still desired;
since in many research cases, the amount of available sample is quite limited.
Currently, the established procedures for ABA analysis involve the detaching
of tissues from the plants, which may induce some changes in phytohormonal
level. Also, the samples are usually homogenized in the extraction solvent with
the quantified results showing only the average ABA level in the whole tissue (Bai
et al. 2010 ). However, in-depth investigation of the molecular mechanism has
uncovered the temporal and spatial patterns of phytohormones signaling in plants.
To date, there have no established methods to follow the in situ and real-time
changes in endogenous ABA concentration, the introduction of some new analyti-
cal techniques, such as the microminiaturization of biosensor probes, sequence-
specific DNA biosensors and in vivo imaging may contribute to its realization.
Acknowledgments The work in the authors laboratory was financially supported by Natural
Science Foundation of China (Grants 90817101, 91117006 and 91317312), Scientific Research
Fund of Hunan Provincial Education Department (12K060, 12K061) and Program for Science
and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province.
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