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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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Related in: MedlinePlus

Transcript level for the genes encoding AlaAT homologues in shoots of wheat seedlings subjected to hypoxia. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings i.e. grown under optimal conditions and harvested 24, 48, 72, 96 and 120 h after induction of hypoxia. Development of hypoxia has been monitored by quantification of the response of gene encoding alcohol dehydrogenase (ADH1). Relative mRNA concentration is expressed in arbitrary units corresponding to the ratio of cDNA copy number of studied gene/18S rRNAcDNA copy number and presented as % of the relative mRNA concentration in control seedlings i.e. grown under optimal conditions. Results are the mean of three replicates ± SD
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Fig3: Transcript level for the genes encoding AlaAT homologues in shoots of wheat seedlings subjected to hypoxia. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings i.e. grown under optimal conditions and harvested 24, 48, 72, 96 and 120 h after induction of hypoxia. Development of hypoxia has been monitored by quantification of the response of gene encoding alcohol dehydrogenase (ADH1). Relative mRNA concentration is expressed in arbitrary units corresponding to the ratio of cDNA copy number of studied gene/18S rRNAcDNA copy number and presented as % of the relative mRNA concentration in control seedlings i.e. grown under optimal conditions. Results are the mean of three replicates ± SD

Mentions: Expression profiles of AlaATs were studied by real-time quantitative PCR in shoots and roots of wheat seedlings subjected to hypoxia. The gene encoding the 18S rRNA has been used as a constitutive control. The obtained results referred to relative mRNA concentration were expressed in arbitrary unit (AU) corresponding to the ratio of cDNA copy number of studied gene/18S rRNA cDNA copy number. Changes in transcript levels are presented as percentage of the relative mRNA concentration in control plants. Development of hypoxic metabolism in young wheat seedlings has been monitored by quantification of the response of gene encoding the fermentative enzyme, alcohol dehydrogenase 1 (ADH1). In response to oxygen deficiency, the concentration of mRNA for ADH1 started to increase in shoots of wheat seedlings after 72 h of hypoxic treatment (Fig. 3), whereas in roots of wheat seedlings after 48 h of hypoxic treatment (Fig. 4).Fig. 3


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 seedlings subjected to hypoxia. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings i.e. grown under optimal conditions and harvested 24, 48, 72, 96 and 120 h after induction of hypoxia. Development of hypoxia has been monitored by quantification of the response of gene encoding alcohol dehydrogenase (ADH1). Relative mRNA concentration is expressed in arbitrary units corresponding to the ratio of cDNA copy number of studied gene/18S rRNAcDNA copy number and presented as % of the relative mRNA concentration in control seedlings i.e. grown under optimal conditions. Results are the mean of three replicates ± SD
© Copyright Policy
Related In: Results  -  Collection

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

Fig3: Transcript level for the genes encoding AlaAT homologues in shoots of wheat seedlings subjected to hypoxia. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of control seedlings i.e. grown under optimal conditions and harvested 24, 48, 72, 96 and 120 h after induction of hypoxia. Development of hypoxia has been monitored by quantification of the response of gene encoding alcohol dehydrogenase (ADH1). Relative mRNA concentration is expressed in arbitrary units corresponding to the ratio of cDNA copy number of studied gene/18S rRNAcDNA copy number and presented as % of the relative mRNA concentration in control seedlings i.e. grown under optimal conditions. Results are the mean of three replicates ± SD
Mentions: Expression profiles of AlaATs were studied by real-time quantitative PCR in shoots and roots of wheat seedlings subjected to hypoxia. The gene encoding the 18S rRNA has been used as a constitutive control. The obtained results referred to relative mRNA concentration were expressed in arbitrary unit (AU) corresponding to the ratio of cDNA copy number of studied gene/18S rRNA cDNA copy number. Changes in transcript levels are presented as percentage of the relative mRNA concentration in control plants. Development of hypoxic metabolism in young wheat seedlings has been monitored by quantification of the response of gene encoding the fermentative enzyme, alcohol dehydrogenase 1 (ADH1). In response to oxygen deficiency, the concentration of mRNA for ADH1 started to increase in shoots of wheat seedlings after 72 h of hypoxic treatment (Fig. 3), whereas in roots of wheat seedlings after 48 h of hypoxic treatment (Fig. 4).Fig. 3

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