Secondary Metabolism in Amaranthus spp. — A Genomic Approach to Understand Its Diversity and Responsiveness to Stress in Marginally Studied Crops with High Agronomic Potential

Abstract

Cultivated amaranths are crops with an unrealized agronomical potential despite their high nutritional value and nutraceutic properties of their seeds and/ or leaves.They tolerate growing conditions unsuitable for cereals, and are tolerant to biotic aggressors. Several Amaranthus species are abundant of sources of secondary metabolites, mostly phenylpropanoids, predominantly in seeds and leaves, many of which may confer health benefits associated with their antioxidant properties. They could also act as defensive compounds against predators or pathogens. Recent biochemical and molecular approaches partly defined the mechanisms responsible for grain amaranth´s tolerance against biotic stress. However, the role played by secondary metabolites in (a)biotic stress amelioration in amaranth is practically unknown. Our group has identified several genes coding for enzymes involved in secondary metabolism pathways in A. hypochondriacus, in addition to related regulatory transcription factors. More than 50% of these genes involve the phenylpropanoid pathway. In this chapter, the role played by this pathway in (a)biotic stress amelioration in plants will be briefly reviewed, followed by an examination of its involvement in the conferral of nutraceutic properties to amaranth plants. A description of the progress obtained so far regarding the characterization of phenylpropanoid genes in grain amaranth will close this chapter.

Drought tolerance promoted by complementation of ascorbate‐glutathione system and antioxidant‐rich phytochemicals in Amaranthus hypochondriacus L.

“…Amaranths are often described as aggressive stress tolerant plant showing a wide range of tolerance, particularly against temperature and drought 7–9 . The germplasms of Amaranthus hypochondriacus L., in particular, showed wide adaptability towards adverse temperature and soil water deficit conditions due to their C 4 photosynthetic character, indeterminate flowering habit, and significantly better water use efficiency 10–14 . However, there is a scant report on drought stress tolerance of Amaranths, that advocates the role of dehydration on the basic physiological performance of the crop 9,15 …”

“…[7][8][9] The germplasms of Amaranthus hypochondriacus L., in particular, showed wide adaptability towards adverse temperature and soil water deficit conditions due to their C 4 photosynthetic character, indeterminate flowering habit, and significantly better water use efficiency. [10][11][12][13][14] However, there is a scant report on drought stress tolerance of Amaranths, that advocates the role of dehydration on the basic physiological performance of the crop. 9,15 Depending on the severity and duration of dehydration stress and plant's ability to withstand such conditions, metabolic change occurs.…”

Antioxidant and Antimicrobial Effects of Baby Leaves of Amaranthus tricolor L. Harvested as Vegetable in Correlation with Their Phytochemical Composition

“…Valentina). A total of 41 metabolites were indicated, including amino acids, organic acids, phenolic acids and fatty acids [ 8 , 9 ]. A. tricolor is a source of a rare group of highly bioactive compounds—betacyanins [ 10 , 11 ], which are not common in nature.…”

Chemical and Bioactive Features of Amaranthus caudatus L. Flowers and Optimized Ultrasound-Assisted Extraction of Betalains

“…Unlike anthocyanins, betalains are not dispersed by a huge range of plant species [ 4 ], but they can be found in different plant tissues of flowers, fruits, stems, leaves and even in seeds [ 5 ]. Betacyanins, a more specific subgroup of betalains, are responsible for the bright pink colour of the plants, aiming at attracting different animals as pollinating or seed dispersing agents [ 6 ]. These secondary metabolites have been extensively explored, due to the exhaustive search of the industry for natural colouring agents, caused by the recent limitations imposed by legislators regarding the side effects of artificial compounds and also due to the consumer´s demand for safer and healthier products [ 7 ].…”