Glycine betaine biosynthesis in saltbushes (Atriplex spp.) under salinity stress

Abstract

Soil salinity and drought severely affect all aspects of plant physiology, leading to significant losses of crop productivity and native biodiversity. A key to sustainable land use in such areas is to cultivate well-adapted native plants that are also commercially important and have the appropriate gene pool. Glycine betaine (GB) is an osmoprotectant that imparts salt and drought tolerance to some plants. It is also shown separately to provide significant health benefits to animals and humans. We investigated whether Australian saltbushes, which are extremely salt and drought tolerant and also impart health benefits to grazing animals, may have the genetic basis for GB biosynthesis, explaining the two different observations. Complementary DNAs encoding the two key enzymes of the plant GB biosynthesis pathway, choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH), were identified and analysed from Atriplex nummularia and Atriplex semibaccata. The sequences showed the putative CMO proteins exhibited all functionally important features including the Reiske-type cluster (2Fe-2S) and mononuclear non-heme Fe cluster, and the putative BADHs exhibited conservation of active site residues. The expression of both genes was found to be significantly up-regulated in leaf tissues under salt stress. The leaf tissues also showed accumulation of very high levels of GB, at 29.69 mmol/kg fresh weight for A. nummularia and 42.68 mmol/kg fresh weight for A. semibaccata, which is several times higher than in cereal crops. The results demonstrate a strong potential of cultivation of saltbushes for re-vegetation and as a perennial fodder in salinity and drought-affected areas.

Characterization of two Winter wheat varieties' responses to freezing in a frigid region of China

“…(Xing and Rajashekar 2001), tomato (Park et al 2006), and wheat (Ma et al 2006). It maintains the water balance between plant cells and the environment and stabilizes macromolecules, enzyme activities, and membranes under stress conditions (Joseph et al 2013). Alteration of the lipid composition of the cell membrane is known to be associated with low temperature tolerance as cell membranes are the first sites of injury (Liu et al 2008).…”

iTRAQ protein profile analysis of leaves and roots of sugar beet (Beta vulgaris) differing in response to salt stress

“…Glycine betaine is considered to be the best osmotic regulator, which is not only involved in the osmotic regulation of cells, but also plays an important role in stabilizing the structure and functions of biological macromolecules under osmotic conditions, such as protecting the major enzymes and terminal oxidases of TCA (tricarboxylic acid) cycle and stabilizing the peripheral peptides of the light system under salt stress. Betaine is an important osmotic regulator, which is produced from choline through two-step oxidation in plants [23][24][25] . The synthesis of betaine is catalyzed by two enzymes, choline monooxygenase (Q4H1G6) and betaine aldehyde dehydrogenase (Q4H1G7), which are significantly up-regulated under salt-stress.…”

iTRAQ protein profile analysis of sugar beet under salt stress: different coping mechanisms in leaves and roots

“…For example, it protects the major enzymes and terminal oxidases of the TCA (tricarboxylic acid) cycle and stabilizes the peripheral peptides of the light system [24][25][26] . In plants, betaine is produced from choline via two oxidation steps and catalyzed by two enzymes that are signi cantly up-regulated under salt-stress: choline monooxygenase (Q4H1G6) and betaine aldehyde dehydrogenase (Q4H1G7) [27][28][29] . In addition, SEX4 (STARCH-EXCESS 4, also known as Dual speci city protein phosphatase 4, DSP4) (A0A0J8B9Z0) acts as a bridge between light-induced redox changes and protein phosphorylation in the regulation of starch accumulation [30] .…”