Plant Metabolomics: An Overview of the Role of Primary and Secondary Metabolites against Different Environmental Stress Factors

Abstract

Several environmental stresses, including biotic and abiotic factors, adversely affect the growth and development of crops, thereby lowering their yield. However, abiotic factors, e.g., drought, salinity, cold, heat, ultraviolet radiations (UVr), reactive oxygen species (ROS), trace metals (TM), and soil pH, are extremely destructive and decrease crop yield worldwide. It is expected that more than 50% of crop production losses are due to abiotic stresses. Moreover, these factors are responsible for physiological and biochemical changes in plants. The response of different plant species to such stresses is a complex phenomenon with individual features for several species. In addition, it has been shown that abiotic factors stimulate multi-gene responses by making modifications in the accumulation of the primary and secondary metabolites. Metabolomics is a promising way to interpret biotic and abiotic stress tolerance in plants. The study of metabolic profiling revealed different types of metabolites, e.g., amino acids, carbohydrates, phenols, polyamines, terpenes, etc, which are accumulated in plants. Among all, primary metabolites, such as amino acids, carbohydrates, lipids polyamines, and glycine betaine, are considered the major contributing factors that work as osmolytes and osmoprotectants for plants from various environmental stress factors. In contrast, plant-derived secondary metabolites, e.g., phenolics, terpenoids, and nitrogen-containing compounds (alkaloids), have no direct role in the growth and development of plants. Nevertheless, such metabolites could play a significant role as a defense by protecting plants from biotic factors such as herbivores, insects, and pathogens. In addition, they can enhance the resistance against abiotic factors. Therefore, metabolomics practices are becoming essential and influential in plants by identifying different phytochemicals that are part of the acclimation responses to various stimuli. Hence, an accurate metabolome analysis is important to understand the basics of stress physiology and biochemistry. This review provides insight into the current information related to the impact of biotic and abiotic factors on variations of various sets of metabolite levels and explores how primary and secondary metabolites help plants in response to these stresses.

Characterization of polyphenols and carbohydrates exuded by Phaeodactylum tricornutum diatom grown under Cu stress

“…However, prolonged exposure periods decreased extracellular carbohydrates in control and sublethal Cu level experiments and increased them under lethal conditions (Table 3 ). These results are consistent with those previously reported by Santiago-Díaz et al for amino acids 25 , primary metabolites essential in the growth and development functions of microorganisms 41 , which decreased during the growth phase of highest biomass accumulation in control cells and under sublethal Cu concentrations and increased under lethal conditions. Under the latter conditions, cells survive by decreasing various cellular activities, such as growth, and focusing on defense mechanisms 32 , 42 .…”

“…Our study showed that carbohydrates exuded by cells increased up to 30- and 107.4-fold in the medium enriched with lethal Cu concentrations after 18 days compared to the control (Table 3 ). This increased carbohydrate exudation may reduce Cu ion activities in the surrounding medium and may facilitate Cu detoxification mechanisms by changing its speciation, improving the tolerance of P. tricornutum to Cu stress 41 , 43 – 45 . In addition, carbohydrates have also been reported to be involved in other metal detoxification mechanisms such as direct quenching of ROS 46 and biotransformation of Cu(II) into less soluble and less toxic CuS 47 .…”

Extractions of aerial parts of Hippomarathrum scabrum with conventional and green methodologies: Chemical profiling, antioxidant, enzyme inhibition, and anti‐cancer effects

“…Nevertheless, it should be taken into account that their content can be influenced by many factors, in the first place by internal and external factors of the plant itself, as well as by the applied extraction techniques and extraction conditions [26]. In other words, the conditions in which the plant grows, abiotic and biotic stress, soil quality, soil fertilization, and climatic conditions influence the production of secondary metabolites as well as their concentration in plants [27–29]. Further, the choice of extraction technique, solvent, and extraction conditions can favor the extraction of certain biomolecules.…”

Effect of Organic and Bio-Fertilization on Fruit Yield, Bioactive Constituents, and Estragole Content in Fennel Fruits

“…Phenolics and flavonoids are valuable bioactive constituents in F. vulgare fruits that act as antioxidants and have various protective and therapeutic effects [22,75,76]. Data from Table 3 show that application of different fertilizers positively enhanced the TPC and TFC compared to unfertilized fennel in both seasons.…”

“…Phenols and flavonoids act as natural antioxidants and protect human cells from harmful molecules such as estragole [20]. The content of these bioactive antioxidants can change dramatically between fennel ecotypes [21] as well as nutrient treatments [19,22].…”