Effect of sulfur availability on the integrity of amino acid biosynthesis in plants

Abstract

Amino acid levels in plants are regulated by a complex interplay of regulatory circuits at the level of enzyme activities and gene expression. Despite the diversity of precursors involved in amino acid biosynthesis as providing the carbon backbones, the amino groups and, for the amino acids methionine and cysteine, the sulfhydryl group and despite the involvement of amino acids as substrates in various downstream metabolic processes, the plant usually manages to provide relatively constant levels of all amino acids. Here we collate data on how amino acid homeostasis is shifted upon depletion of one of the major biosynthetic constituents, i.e., sulfur. Arabidopsis thaliana seedlings exposed to sulfate starvation respond with a set of adaptation processes to achieve a new balance of amino acid metabolism. First, metabolites containing reduced sulfur (cysteine, glutathione, S-adenosylmethionine) are reduced leading to a number of downstream effects. Second, the relative excess accumulation of N over S triggers processes to dump nitrogen in asparagine, glutamine and further N-rich compounds like ureides. Third, the depletion of glutathione affects the redox and stress response system of the glutathione-ascorbate cycle. Thus, biosynthesis of aromatic compounds is triggered to compensate for this loss, leading to an increased flux and accumulation of aromatic amino acids, especially tryptophan. Despite sulfate starvation, the homeostasis is kept, though shifted to a new state. This adaptation process keeps the plant viable even under an adverse nutritional status.

Cooperative Ethylene and Jasmonic Acid Signaling Regulates Selenite Resistance in Arabidopsis

“…It is known that reduced organic S metabolites compose a large fraction of the S pool (Nikiforova et al, 2006). To determine whether levels of reduced organic S metabolites are affected by selenite treatment, the levels of nonprotein thiols were measured in shoot tissue.…”

“…A large fraction of the nonprotein thiol pool consists of glutathione, which is involved in regulating the redox state of the cell as well as the storage and transport of reduced S in plants (Nikiforova et al, 2006). While the level of reduced glutathione (GSH) was not affected by selenite treatment in Col-0, it was nearly 2-fold lower in selenite-treated Ws-2 compared to control conditions and to selenite-treated Col-0 plants (Fig.…”

Impacts of root sulfate deprivation on growth and elements concentration of globe amaranth (Gomphrena globosa L.) under hydroponic condition

“…But up to now, there was no direct evidence that could prove the phenomena shown in the case of globe amaranth (Gomphrena globosa L.); to explore the plant atmospheric sulfides utilization characteristics directly with the physiological and biological approaches was thus certainly what should be done next, for sulfate starvation of plants led to a series of metabolic and physiological responses aiming at adopting plant metabolism to the available nutrient supply and to acquire a new homeostatic balance (Nikiforova et al 2005). After all, the primary target site for effects of sulfate deprivation were the S containing metabolites, the amino acids cysteine and methionine and their immediate derived metabolites such as GSH and SAM (Nikiforova et al 2006). Amino acid content in plants was usually balanced in a delicate way (Hofgen et al 1995).…”

“…S is usually taken up as sulfate (Nikiforova et al 2006). Generally, plants utilize sulfate taken up by the roots as an S source for growth and sulfurdeficient plants generate a lower yield and quality (Lunde et al 2008).…”

The contents of free amino acids and elements in As-hyperaccumulator Pteris cretica and non-hyperaccumulator Pteris straminea during reversible senescence

“…Similarly, sarcosine, which is found in some hyperaccumulators, was not detected. This AA is linked with methyl metabolism and affects epigenetic changes induced by oxidative stress (Nikiforova et al 2006. The contents of other identified AAs (γ-aminobutyric acid, lysine, α-aminoadipic acid, ornithine, tryptophan, valine and tyrosine) oscillated around the detection limit and therefore they were not evaluated using the principal component analysis (PCA).…”