Abiotic Stress Responses in Plants: Unraveling the Complexity of Genes and Networks to Survive - Abiotic Stress: Plant Responses and Applications in Agriculture - page 74

These three simple examples illustrate the advantages of the use of (differential) proteomics
to study the effects of different abiotic stresses such as water deficit, temperature or UV
exposure. Results show a large number of proteins being affected by abiotic stresses and the
metabolic pathways that are subsequently affected and at what levels they are affected. The
advantages of proteomics are further highlighted by the possibility to study PTMs of key
importance in plant's physiological and biochemical responses to stress.
5.3. Metabolomics
Higher plants have the remarkable ability to synthesize a vast array of compounds that differ
in chemical complexity and biological activity, playing indispensable roles in chemical
defenses against biotic and abiotic stresses [301, 302]. In such context, it is obvious that
Metabolomics (i.e. the study of the metabolome, or the set of metabolites found in a given plant
tissue or organ) plays a significant role in bridging the phenotype-genotype gap [303]. The
increasing number of publications in this subject also supports that metabolomics is not just a
new Omics but a valuable tool to study phenotypes and changes in phenotypes induced by
biotic and abiotic stresses (reviewed in [303]).
Metabolomics experiments start with the acquisition of metabolic fingerprints or metabolite
profiles using various analytical instruments and separation technologies based in the physic-
chemical properties of each metabolite [280]. Since there is no single technology currently
available (or likely in the near future) to detect all compounds found in plants or any other
organism, a combination of multiple analytical techniques, such as gas chromatography (GC),
liquid chromatography (LC), capillary electrophoresis (CE) coupled to Mass Spectrometry
(MS), and Nuclear Magnetic Resonance (NMR) are generally performed following established
protocols (reviewed in [280, 301]).
Metabolomic profiling of plants under stress is an important approach to study stress induced
change in metabolites pools. In most of these studies, metabolite profiles are analyzed in
combination with transcriptomic analysis: a strong correlation between metabolite levels is
often correlated to a specific gene underlying a specific response or phenotype observed [280,
304]. In the recent past, the majority of the metabolic works have occurred in model species
such as Arabidopsis [305] but nowadays, such metabolomic technologies are being used with
success in forages [306], cereals [307] and other food crops [308].
Common bean ( Phaseolus vulgaris L.) is one of the most important legume crops for human
consumption but its productivity is often limited by low Phosphorus (P) levels in the soil [309].
Coupled to a transcriptomic approach, a non-biased metabolite profiling of bean roots using
GC-MS was done to assess the degree to which changes in gene expression in P-deficient roots
affect overall metabolism [308]. A total of 81 metabolites were detected and 42 were differen‐
tially expressed between −P to +P response ratios. Stress related metabolites identified such as
polyols accumulated in P-deficient roots as well as sugars, providing additional support for
the role of these compounds for P stress. The metabolomic data supported the identification
of candidate genes involved in common bean root adaptation to P deficiency to be used in
improvement programs.