Lysine metabolism and amino acid profile in maize grains from plants subjected to cadmium exposure

Abstract

In general, the effects of Cadmium (Cd) on crop quality are evaluated solely by Cd accumulation in the edible plant parts; thus, the potential effects on several nutritional features are not often taken into account. This study evaluated Cd effects on the enzymatic activities of lysine (Lys) metabolism, storage protein and amino acid profile in maize. Stress parameters were also assessed. In vegetative organs, Cd was accumulated in the following decreasing order: roots > stems > leaves. Cadmium accumulation in grains decreased at grain maturity (from 0.25 to 0.07 µg g-1 DW). In leaves, neither hydrogen peroxide content nor superoxide dismutase, catalase, ascorbate peroxide and guaiacol peroxidase activities did not change in Cd-treated plants compared to control plants. Lipid peroxidation was not detected in immature grains and leaves of plants under Cd exposure, indicating that Cd accumulation mainly in the roots is a mechanism to avoid oxidative stress in aboveground parts of the plant. However, Lys metabolism in immature grains was modified, showing increases in the specific activities of aspartate kinase (AK) and dihydrodipicolinate synthase (DHDPS) after Cd exposure. AK sensitivity to Lys feedback inhibition increased, but decreased in DHDPS in Cd-treated plants, suggesting differential regulation for these enzymes. In mature grains, the Lys content did not change, while the proline content increased by 54 % in Cd-treated plants. This is the first report on Cd effects on amino acid profile, storage protein contents and enzymes from Lys metabolism in grains of a cereal plant species.

Nitrate improves hackberry seedling growth under cadmium application

“…Increase in tissue's fresh weight is generally associated with changes in cell metabolism and increase in some cell protective osmolites such as soluble carbohydrates, organic nitrogen compounds (peptides, amides and amino acids) and some phytohormones (Poschenrieder and Barcel o, 2004;Guo et al, 2019;Liu et al, 2019). Organic nitrogen compounds have unique role in sequestering and inactivation of toxic metals (Srivastava et al, 2004;Rady et al, 2019;Kato et al, 2019), and the role of phytochlatines has been well established in this regard (Cobbett and Goldsbrough, 2002;Marschner, 2011). It was shown that cadmium deposits extracellularly in some cell walls, and intracellularly on the inner surfaces of xylem vessels and some cytoplasm, in the root tip of two species of Iris L. treated with 1000 mg L À1 Cd in comparison to cells in control plants (Han et al, 2007).…”

The sweet side of misbalanced nutrients in cadmium‐stressed plants

“…Roots, which generally have higher Cd concentrations than do shoots (Kato, Carvalho, Gaziola, Piotto, & Azevedo, ; Piotto et al, ), should be able to quickly activate protective mechanisms to counteract the entrance of positive charges originating from Cd accumulation. One of these mechanisms is probably associated with reducing concentrations of positively charged nutrients in roots; this mechanism can involve enhancing translocation of Mn (and also Zn) from roots to shoots (Borges et al, ; Carvalho, Piotto, Franco, ; Carvalho et al, ) (Figures and ) and may be further potentiated by either decreasing uptake (Carvalho, Piotto, Gaziola, et al, ) or increasing exclusion in the root system.…”

Cadmium effects on plant reproductive organs: Physiological, productive, evolutionary and ecological aspects

“…Cadmium‐induced effects on the grain amino acid profile from maize plants under Cd exposure depended on genotype and developmental stage of grains: while maize CML‐161 presented low degree of variations in mature grains (Kato, Carvalho, Gaziola, Piotto, & Azevedo, 2020), the maize cv. AL Avaré exhibited significant increments in histidine, glycine, tyrosine, methionine and isoleucine concentrations in the developing grains (Group's unpublished results).…”