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Differential regulation of alanine aminotransferase homologues by abiotic stresses in wheat (Triticum aestivum L.) seedlings.

Kendziorek M, Paszkowski A, Zagdańska B - Plant Cell Rep. (2012)

Bottom Line: Nitrogen deficiency has little effect on the activity of GGAT.Both AlaAT and GGAT activities were present in etiolated wheat seedlings but their activity was half of that observed in light-grown seedlings.It is proposed that hypoxia-induced AlaAT1 and light-induced peroxisomal GGAT1 appears to be crucial for the regulation of energy availability in plants grown under unfavourable environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Biochemistry Department, Warsaw University of Life Sciences, Nowoursynowska 159, 02-776 Warsaw, Poland.

ABSTRACT
Wheat (Triticum aestivum L.) seedlings contain four alanine aminotransferase (AlaAT) homologues. Two of them encode AlaAT enzymes, whereas two homologues act as glumate:glyoxylate aminotransferase (GGAT). To address the function of the distinct AlaAT homologues a comparative examination of the changes in transcript level together with the enzyme activity and alanine and glutamate content in wheat seedlings subjected to low oxygen availability, nitrogen and light deficiency has been studied. Shoots of wheat seedlings were more tolerant to hypoxia than the roots as judging on the basis of enzyme activity and transcript level. Hypoxia induced AlaAT1 earlier in roots than in shoots, while AlaAT2 and GGAT were unaffected. The increase in AlaAT activity lagged behind the increase in alanine content. Nitrogen deficiency has little effect on the activity of GGAT. In contrast, lower activity of AlaAT and the level of mRNA for AlaAT1 and AlaAT2 in wheat seedlings growing on a nitrogen-free medium seems to indicate that AlaAT is regulated by the availability of nitrogen. Both AlaAT and GGAT activities were present in etiolated wheat seedlings but their activity was half of that observed in light-grown seedlings. Exposure of etiolated seedlings to light caused an increase in enzyme activities and up-regulated GGAT1. It is proposed that hypoxia-induced AlaAT1 and light-induced peroxisomal GGAT1 appears to be crucial for the regulation of energy availability in plants grown under unfavourable environmental conditions. Key message In young wheat seedlings, both AlaAT and GGAT are down-regulated by nitrogen deficiency, whereas AlaAT1 is upregulated by hypoxia and GGAT1 by light.

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Transcript level for the genes encoding AlaAT homologues in shoots of wheat subjected to nitrogen deprivation. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings and seedlings harvested 24, 48, 72, 96 and 120 h after transfer to a nitrogen-free medium. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated. Results are the mean of three replicates ± SD
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Fig8: Transcript level for the genes encoding AlaAT homologues in shoots of wheat subjected to nitrogen deprivation. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings and seedlings harvested 24, 48, 72, 96 and 120 h after transfer to a nitrogen-free medium. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated. Results are the mean of three replicates ± SD

Mentions: To investigate the impact of nitrogen deprivation on AlaAT, the changes in transcript levels, enzyme specific activity and a quantitative gel assays were studied in shoots and roots of wheat seedlings grown in the absence of nitrates after 14 days of growth in the presence of nitrates in Knop solution. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated (Figs. 8, 9). In response to N-deficiency, a rapid decrease in concentration of mRNA for NR was observed in both roots and shoots of wheat seedlings, the effect being more pronounced for wheat shoots.Fig. 8


Differential regulation of alanine aminotransferase homologues by abiotic stresses in wheat (Triticum aestivum L.) seedlings.

Kendziorek M, Paszkowski A, Zagdańska B - Plant Cell Rep. (2012)

Transcript level for the genes encoding AlaAT homologues in shoots of wheat subjected to nitrogen deprivation. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings and seedlings harvested 24, 48, 72, 96 and 120 h after transfer to a nitrogen-free medium. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated. Results are the mean of three replicates ± SD
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351597&req=5

Fig8: Transcript level for the genes encoding AlaAT homologues in shoots of wheat subjected to nitrogen deprivation. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings and seedlings harvested 24, 48, 72, 96 and 120 h after transfer to a nitrogen-free medium. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated. Results are the mean of three replicates ± SD
Mentions: To investigate the impact of nitrogen deprivation on AlaAT, the changes in transcript levels, enzyme specific activity and a quantitative gel assays were studied in shoots and roots of wheat seedlings grown in the absence of nitrates after 14 days of growth in the presence of nitrates in Knop solution. Transcription level of nitrate reductase (NR) as a marker gene for nitrogen starvation was investigated (Figs. 8, 9). In response to N-deficiency, a rapid decrease in concentration of mRNA for NR was observed in both roots and shoots of wheat seedlings, the effect being more pronounced for wheat shoots.Fig. 8

Bottom Line: Nitrogen deficiency has little effect on the activity of GGAT.Both AlaAT and GGAT activities were present in etiolated wheat seedlings but their activity was half of that observed in light-grown seedlings.It is proposed that hypoxia-induced AlaAT1 and light-induced peroxisomal GGAT1 appears to be crucial for the regulation of energy availability in plants grown under unfavourable environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Biochemistry Department, Warsaw University of Life Sciences, Nowoursynowska 159, 02-776 Warsaw, Poland.

ABSTRACT
Wheat (Triticum aestivum L.) seedlings contain four alanine aminotransferase (AlaAT) homologues. Two of them encode AlaAT enzymes, whereas two homologues act as glumate:glyoxylate aminotransferase (GGAT). To address the function of the distinct AlaAT homologues a comparative examination of the changes in transcript level together with the enzyme activity and alanine and glutamate content in wheat seedlings subjected to low oxygen availability, nitrogen and light deficiency has been studied. Shoots of wheat seedlings were more tolerant to hypoxia than the roots as judging on the basis of enzyme activity and transcript level. Hypoxia induced AlaAT1 earlier in roots than in shoots, while AlaAT2 and GGAT were unaffected. The increase in AlaAT activity lagged behind the increase in alanine content. Nitrogen deficiency has little effect on the activity of GGAT. In contrast, lower activity of AlaAT and the level of mRNA for AlaAT1 and AlaAT2 in wheat seedlings growing on a nitrogen-free medium seems to indicate that AlaAT is regulated by the availability of nitrogen. Both AlaAT and GGAT activities were present in etiolated wheat seedlings but their activity was half of that observed in light-grown seedlings. Exposure of etiolated seedlings to light caused an increase in enzyme activities and up-regulated GGAT1. It is proposed that hypoxia-induced AlaAT1 and light-induced peroxisomal GGAT1 appears to be crucial for the regulation of energy availability in plants grown under unfavourable environmental conditions. Key message In young wheat seedlings, both AlaAT and GGAT are down-regulated by nitrogen deficiency, whereas AlaAT1 is upregulated by hypoxia and GGAT1 by light.

Show MeSH
Related in: MedlinePlus