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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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Light induction of transcription of the genes encoding AlaAT homologues. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of etiolated seedlings and seedlings transferred for 2 or 4 days to light in comparison to control seedlings i.e. grown for 6 days in normal light conditions. Results are the mean of three replicates ± SD
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Fig12: Light induction of transcription of the genes encoding AlaAT homologues. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of etiolated seedlings and seedlings transferred for 2 or 4 days to light in comparison to control seedlings i.e. grown for 6 days in normal light conditions. Results are the mean of three replicates ± SD

Mentions: To investigate light induction of AlaAT and GGAT in wheat seedlings, a comparison of transcript levels and enzyme activity in dark-grown seedlings and exposed to light was performed (Fig. 12). The highest mRNA concentration for genes encoding AlaAT homologues was observed in shoots of wheat seedlings growing for 6 days upon light (control seedlings). The transcription of genes encoding GGAT1 and GGAT2 was strongly depressed in darkness. Concentration of mRNA for GGAT1 and GGAT2 was lowest in shoots of etiolated seedlings, i.e. germinating in dark for 6 days, whereas the mRNA level for the gene encoding AlaAT1 was similar in dark- and light-grown seedlings. The inhibitory effect of darkness was reversible by light: in light-grown seedlings for 2 days the transcript levels for GGAT1 and GGAT2 were about nine- and twofold higher, respectively. Prolonged exposition of seedlings to light up to 4 days reversed almost completely the inhibitory effect of darkness in the case of GGAT1 transcripts.Fig. 12


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)

Light induction of transcription of the genes encoding AlaAT homologues. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of etiolated seedlings and seedlings transferred for 2 or 4 days to light in comparison to control seedlings i.e. grown for 6 days in normal light conditions. Results are the mean of three replicates ± SD
© Copyright Policy
Related In: Results  -  Collection

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

Fig12: Light induction of transcription of the genes encoding AlaAT homologues. Quantitive Real Time PCR was performed on cDNA synthesized on the basis of total RNA extracted from shoots of etiolated seedlings and seedlings transferred for 2 or 4 days to light in comparison to control seedlings i.e. grown for 6 days in normal light conditions. Results are the mean of three replicates ± SD
Mentions: To investigate light induction of AlaAT and GGAT in wheat seedlings, a comparison of transcript levels and enzyme activity in dark-grown seedlings and exposed to light was performed (Fig. 12). The highest mRNA concentration for genes encoding AlaAT homologues was observed in shoots of wheat seedlings growing for 6 days upon light (control seedlings). The transcription of genes encoding GGAT1 and GGAT2 was strongly depressed in darkness. Concentration of mRNA for GGAT1 and GGAT2 was lowest in shoots of etiolated seedlings, i.e. germinating in dark for 6 days, whereas the mRNA level for the gene encoding AlaAT1 was similar in dark- and light-grown seedlings. The inhibitory effect of darkness was reversible by light: in light-grown seedlings for 2 days the transcript levels for GGAT1 and GGAT2 were about nine- and twofold higher, respectively. Prolonged exposition of seedlings to light up to 4 days reversed almost completely the inhibitory effect of darkness in the case of GGAT1 transcripts.Fig. 12

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