Abiotic Stress in Plants and Metabolic Responses - Abiotic Stress: Plant Responses and Applications in Agriculture - page 31

Metabolomic analyses have been applied to the functional identification of unknown
genes through metabolic profiling of plants in which some genes are up- or down-regu‐
lated, the discovery of biomarkers associated with disease phenotypes, the safety assess‐
ment of genetically modified organisms (GMOs), the characterization of plant metabolites
of nutritional importance and significance in human health, and the discovery of com‐
pounds involved in plant resistance to biotic and abiotic stresses [76]. Metabolic profiles
can be used as signatures for assessing the genetic variation among different cultivars or
species of the same genotype at different growth stages and environments. The metabo‐
lite profile represents phenotypic information; this means that qualitative and quantita‐
tive metabolic measurements can be related to the genotypes of the plants to differentiate
closely related individuals [77, 78]. Once the identification of individual metabolites is
available, connections among metabolites can be established, and then metabolic profiles
can be used to infer mechanisms of defense. Metabolic profiles will guide tailoring of
genotypes for acceptable performance under adverse growth conditions and will be of
help in design and development of crop plant cultivars best suited to sustainable agricul‐
ture [79, 80]. Metabolomics tools have been used to evaluate the impact of the genotype
and the environment on the quality of plant growth in the study of interpecific hybrids
between Jacobaea aquatica and J. vulgaris (common weeds native to Northern Eurasia). An
NMR-based metabolomics profiling approach was used to correlate the expression of
high and low concentrations of particular compounds, including phenylpropanoids and
sugars, with results of quantification of genetically controlled differences between major
primary and secondary metabolites [81]. In melon ( Cucumis melo L.), metabolomic and el‐
emental profiling of fruit quality were found to be affected by genotype and environment
[82].
6. Plant metabolomics and drought stress
The variable and often insufficient rainfalls in extended areas of rain-fed agriculture, the
unsustainable groundwater use for irrigated agriculture worldwide, and the fast-growing
demands for urban water are putting extreme pressure on global food crop production. The
demand for water to sustain the agriculture systems in many countries will continue to increase
as a result of growing populations [83]. This progressively worsening water scarcity is
imposing hydric stress on both rain-fed and irrigated crops. Water deficiency stress induces a
wide range of physiological and biochemical alterations in plants; arrestment of cell growth
and photosynthesis and enhanced respiration are among the early affects. Genome expression
is extensively remodeled, activating and repressing a variety of genes with diverse functions
[11, 84]. Sensing water deficit and activation of defense mechanisms comes through chemical
signals in which abscisic acid (ABA) plays a central role. ABA accumulates in tissues of plants
subjected to hydric stress and promotes transpiration reduction via stomatal closure. Through
this mechanism, plants minimize water losses and diminish stress injury. ABA regulates
expression of many stress-responsive genes, including the late embryogenesis abundant (LEA)
proteins, leading to a reinforcement of drought stress tolerance in plants [85]. Many questions