Amino acid pattern and glutamate metabolism during dehydration stress in the 'resurrection' plant Sporobolus stapfianus: a comparison between desiccation-sensitive and desiccation-tolerant leaves

Abstract

The present study analyses changes in nitrogen compounds, amino acid composition, and glutamate metabolism in the resurrection plant Sporobolus stapfianus during dehydration stress. Results showed that older leaves (OL) were desiccation-sensitive whereas younger leaves (YL) were desiccation-tolerant. OL lost their soluble protein more rapidly, and to a larger extent than YL. Enzymes of primary nitrogen assimilation were affected by desiccation and the decrease in the glutamine synthetase (GS, EC 6.3.1.2) and ferredoxin-dependent GOGAT (Fd-GOGAT, EC 1.4.7.1) activities was higher in OL than in YL, thus suggesting higher sensibility to dehydration. Moreover, YL showed higher total GS enzyme activity at the end of the dehydration stress and was shown to maintain high chloroplastic GS protein content during the entire stress period. Free amino acid content increased in both YL and OL between 88% and 6% relative water content. Interestingly, OL and YL did not accumulate the same amino acids. OL accumulated large amounts of proline and gamma-aminobutyrate whereas YL preferentially accumulated asparagine and arginine. It is concluded (i) that modifications in the nitrogen and amino acid metabolism during dehydration stress were different depending on leaf development and (ii) that proline and gamma-aminobutyrate accumulation in S. stapfianus leaves were not essential for the acquisition of desiccation tolerance. On the contrary, the accumulation of large amounts of asparagine and arginine in the YL during dehydration could be important and serve as essential nitrogen and carbon reservoirs useful during rehydration. In this context, the role of GS for asparagine accumulation in YL is discussed.

Influence of Drought and Wounding Stress on Soluble Phenols and Proteins in Potato Tubers

“…This corresponds with other studies on AAS, e.g. in Brassica napus leaves most of the amino acids showed an increase (up to 5.9-fold) under drought stress (Good & Zaplachinski, 1994) and also in leaves of Sporobolus stapfianus the AAS were enhanced by desiccation stress (Martinelli et al, 2007). These results were not surprising, since amino acids are known to function as osmolytes often used by water stressed organisms to maintain the cell volume and to stabilize proteins and other macromolecules (Yancey, 2001).…”

On the Chemical Profile of Marine Organisms from Coastal Subtropical Environments: Gross Composition and Nitrogen-to-Protein Conversion Factors

“…According to Little (2000), some halophyte plants maintain their cytoplasm in the same osmotic pressure as the cell vacuole, accumulating free AAs such as proline. Martinelli et al (2007) indicate that this feature in Sporobolus stapfianus, a halophilic grass, which accumulate AAs in vaculoes, especially proline, for adaptation to water stress. The amino acid profiles of animals were more heterogeneous than that observed in algae and plants, since significant differences were observed in the concentrations of some AAs as glycine, lysine and arginine.…”

Effect of Solanum surattense seed on the oxidative potential of cauda epididymal spermatozoa

“…The significant depletion in the activity level of GDH in the treated animals indicates the decreased efficiency of the TCA cycle. The GDH forms the important marker enzyme towards the mobilization of several amino acids into TCA cycle [23][24][25] . The citric acid content in the sperm suspension of the seed extract fed rats revealed a significant decrement indicating the reduced oxidative metabolism.…”