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Comparative metabolic responses and adaptive strategies of wheat (Triticum aestivum) to salt and alkali stress.

Guo R, Yang Z, Li F, Yan C, Zhong X, Liu Q, Xia X, Li H, Zhao L - BMC Plant Biol. (2015)

Bottom Line: High-pH of alkali stress induced the most of phosphate and metal ions to precipitate; as a result, the availability of nutrients significantly declined.These outcomes correspond to specific detrimental effects of a highly pH environment.Alkali stress (at high pH) significantly inhibited photosynthetic rate; thus, sugar production was reduced, N metabolism was limited, amino acid production was reduced, and glycolysis was inhibited.

View Article: PubMed Central - PubMed

Affiliation: Institute of Environment and Sustainable Development in Agriculture (IEDA), Chinese Academy of Agricultural Sciences (CAAS)/Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Beijing, 100081, P.R. China. guor219@yahoo.com.

ABSTRACT

Background: It is well known that salinization (high-pH) has been considered as a major environmental threat to agricultural systems. The aim of this study was to investigate the differences between salt stress and alkali stress in metabolic profiles and nutrient accumulation of wheat; these parameters were also evaluated to determine the physiological adaptive mechanisms by which wheat tolerates alkali stress.

Results: The harmful effect of alkali stress on the growth and photosynthesis of wheat were stronger than those of salt stress. High-pH of alkali stress induced the most of phosphate and metal ions to precipitate; as a result, the availability of nutrients significantly declined. Under alkali stress, Ca sharply increased in roots, however, it decreased under salt stress. In addition, we detected the 75 metabolites that were different among the treatments according to GC-MS analysis, including organic acids, amino acids, sugars/polyols and others. The metabolic data showed salt stress and alkali stress caused different metabolic shifts; alkali stress has a stronger injurious effect on the distribution and accumulation of metabolites than salt stress. These outcomes correspond to specific detrimental effects of a highly pH environment.

Conclusions: Ca had a significant positive correlation with alkali tolerates, and increasing Ca concentration can immediately trigger SOS Na exclusion system and reduce the Na injury. Salt stress caused metabolic shifts toward gluconeogenesis with increased sugars to avoid osmotic stress; energy in roots and active synthesis in leaves were needed by wheat to develop salt tolerance. Alkali stress (at high pH) significantly inhibited photosynthetic rate; thus, sugar production was reduced, N metabolism was limited, amino acid production was reduced, and glycolysis was inhibited.

No MeSH data available.


Related in: MedlinePlus

Change in metabolites of the metabolic pathways in leaves of wheat seedlings after 15 d of alkali stress treatment. Proposed metabolic network changes in wheat seedlings subjected to alkali stress, as obtained through OPLS-DA. The metabolites with red boxes denote significant increases; the metabolites with green boxes denote significant decreases (p < 0.05). Salt stress/No salinity stress (S/C); Alkali stress/No salinity stress (A/C); Alkali stress/Salt stress (A/S)
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Fig5: Change in metabolites of the metabolic pathways in leaves of wheat seedlings after 15 d of alkali stress treatment. Proposed metabolic network changes in wheat seedlings subjected to alkali stress, as obtained through OPLS-DA. The metabolites with red boxes denote significant increases; the metabolites with green boxes denote significant decreases (p < 0.05). Salt stress/No salinity stress (S/C); Alkali stress/No salinity stress (A/C); Alkali stress/Salt stress (A/S)

Mentions: Osmotic stress and excessive Na+ affect root functions when plants are subjected to salinity stress, which induces generation of reactive oxygen species (ROS), such as O2−, and causes intracellular hyperammonia [37]. Proline is known to play an important role in higher plants in response to osmotic and salinity stress by protecting plant cell membranes and proteins and functioning as a ROS scavenger [38]. In this study, proline accumulated in the cytoplasm of wheat seedlings in response to salinity stress, helping in balancing the osmotic pressure in the vacuoles in response to influx of Na+. Proline increase was accompanied with a significant decrease in levels of transamination-related metabolites Glu and GABA, implying that salinity stress promotes Glu conversion into proline with Δ1-pyrroline-5-carboxylate synthetase (Figs. 5 and 6). Many studies have shown that the accumulation of some sugars can counter the effects of increased salinity by increasing the osmotic potential to avoid stress [39]. Our results showed that the sugar contents of the wheat seedlings increased in response to salt stress; however, a dramatic decrease in sugar levels was found under alkali stress. In plant cells, sugars were derived from photosynthesis, gluconeogenesis, and degradation of polysaccharides [5, 39]. Since the apparent photosynthetic rate was reported to be similar under control and salt stress, this implies that gluconeogenesis was probably promoted under salt stress to maintain osmotic balance, as well as for sugars to function as carbon storage. The severe negative effect of alkali stress on sugar synthesis and storage may reflect the toxic levels of Na+ accumulating in plant cells in a high-pH environment, implying ROS detoxification capacity had been setback by high pH. Our data suggest that sugar accumulation is not a simple passive response to osmotic stress, but rather a result of active metabolic regulation after sensing high pH levels and corresponding alkali stress indicators.Fig. 5


Comparative metabolic responses and adaptive strategies of wheat (Triticum aestivum) to salt and alkali stress.

Guo R, Yang Z, Li F, Yan C, Zhong X, Liu Q, Xia X, Li H, Zhao L - BMC Plant Biol. (2015)

Change in metabolites of the metabolic pathways in leaves of wheat seedlings after 15 d of alkali stress treatment. Proposed metabolic network changes in wheat seedlings subjected to alkali stress, as obtained through OPLS-DA. The metabolites with red boxes denote significant increases; the metabolites with green boxes denote significant decreases (p < 0.05). Salt stress/No salinity stress (S/C); Alkali stress/No salinity stress (A/C); Alkali stress/Salt stress (A/S)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4492011&req=5

Fig5: Change in metabolites of the metabolic pathways in leaves of wheat seedlings after 15 d of alkali stress treatment. Proposed metabolic network changes in wheat seedlings subjected to alkali stress, as obtained through OPLS-DA. The metabolites with red boxes denote significant increases; the metabolites with green boxes denote significant decreases (p < 0.05). Salt stress/No salinity stress (S/C); Alkali stress/No salinity stress (A/C); Alkali stress/Salt stress (A/S)
Mentions: Osmotic stress and excessive Na+ affect root functions when plants are subjected to salinity stress, which induces generation of reactive oxygen species (ROS), such as O2−, and causes intracellular hyperammonia [37]. Proline is known to play an important role in higher plants in response to osmotic and salinity stress by protecting plant cell membranes and proteins and functioning as a ROS scavenger [38]. In this study, proline accumulated in the cytoplasm of wheat seedlings in response to salinity stress, helping in balancing the osmotic pressure in the vacuoles in response to influx of Na+. Proline increase was accompanied with a significant decrease in levels of transamination-related metabolites Glu and GABA, implying that salinity stress promotes Glu conversion into proline with Δ1-pyrroline-5-carboxylate synthetase (Figs. 5 and 6). Many studies have shown that the accumulation of some sugars can counter the effects of increased salinity by increasing the osmotic potential to avoid stress [39]. Our results showed that the sugar contents of the wheat seedlings increased in response to salt stress; however, a dramatic decrease in sugar levels was found under alkali stress. In plant cells, sugars were derived from photosynthesis, gluconeogenesis, and degradation of polysaccharides [5, 39]. Since the apparent photosynthetic rate was reported to be similar under control and salt stress, this implies that gluconeogenesis was probably promoted under salt stress to maintain osmotic balance, as well as for sugars to function as carbon storage. The severe negative effect of alkali stress on sugar synthesis and storage may reflect the toxic levels of Na+ accumulating in plant cells in a high-pH environment, implying ROS detoxification capacity had been setback by high pH. Our data suggest that sugar accumulation is not a simple passive response to osmotic stress, but rather a result of active metabolic regulation after sensing high pH levels and corresponding alkali stress indicators.Fig. 5

Bottom Line: High-pH of alkali stress induced the most of phosphate and metal ions to precipitate; as a result, the availability of nutrients significantly declined.These outcomes correspond to specific detrimental effects of a highly pH environment.Alkali stress (at high pH) significantly inhibited photosynthetic rate; thus, sugar production was reduced, N metabolism was limited, amino acid production was reduced, and glycolysis was inhibited.

View Article: PubMed Central - PubMed

Affiliation: Institute of Environment and Sustainable Development in Agriculture (IEDA), Chinese Academy of Agricultural Sciences (CAAS)/Key Laboratory of Dryland Agriculture, Ministry of Agriculture, Beijing, 100081, P.R. China. guor219@yahoo.com.

ABSTRACT

Background: It is well known that salinization (high-pH) has been considered as a major environmental threat to agricultural systems. The aim of this study was to investigate the differences between salt stress and alkali stress in metabolic profiles and nutrient accumulation of wheat; these parameters were also evaluated to determine the physiological adaptive mechanisms by which wheat tolerates alkali stress.

Results: The harmful effect of alkali stress on the growth and photosynthesis of wheat were stronger than those of salt stress. High-pH of alkali stress induced the most of phosphate and metal ions to precipitate; as a result, the availability of nutrients significantly declined. Under alkali stress, Ca sharply increased in roots, however, it decreased under salt stress. In addition, we detected the 75 metabolites that were different among the treatments according to GC-MS analysis, including organic acids, amino acids, sugars/polyols and others. The metabolic data showed salt stress and alkali stress caused different metabolic shifts; alkali stress has a stronger injurious effect on the distribution and accumulation of metabolites than salt stress. These outcomes correspond to specific detrimental effects of a highly pH environment.

Conclusions: Ca had a significant positive correlation with alkali tolerates, and increasing Ca concentration can immediately trigger SOS Na exclusion system and reduce the Na injury. Salt stress caused metabolic shifts toward gluconeogenesis with increased sugars to avoid osmotic stress; energy in roots and active synthesis in leaves were needed by wheat to develop salt tolerance. Alkali stress (at high pH) significantly inhibited photosynthetic rate; thus, sugar production was reduced, N metabolism was limited, amino acid production was reduced, and glycolysis was inhibited.

No MeSH data available.


Related in: MedlinePlus