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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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Sequence analysis of AlaAT homologues from wheat. a Alignment of obtained sequences by ClustalX 1.83. b Phylogenetic tree of the AlaAT enzyme family. Comparison was performed using coding sequences of wheat and all fully sequenced for AlaAT genes in Arabidopsis by Clustal W2
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Fig2: Sequence analysis of AlaAT homologues from wheat. a Alignment of obtained sequences by ClustalX 1.83. b Phylogenetic tree of the AlaAT enzyme family. Comparison was performed using coding sequences of wheat and all fully sequenced for AlaAT genes in Arabidopsis by Clustal W2

Mentions: From the wheat genome sequencing information available in the public data domain (TIGR, http://compbio.dfci.harvard.edu/cgi-bin/tgi/gimain.pl?gudb=wheat) it was searched for the the presence of AlaAT isoenzymes using the tBLASTn. Four fragments of cDNA encoding wheat AlaATs corresponding to Arabidopsis genes (At1g72330, At1g17290, At1g23310, At1g70580) were obtained (Fig. 2a). A phylogenetic analysis of AlaAT from Arabidopsisthaliana and Triticum aestivum performed using ClustalW programme (Higgins et al. 1994) showed that two of them were closely related to Arabidopsis AlaAT1 and AlaAT2 while other two appeared to be related to GGAT1 and GGAT2 (Fig. 2b).Fig. 2


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)

Sequence analysis of AlaAT homologues from wheat. a Alignment of obtained sequences by ClustalX 1.83. b Phylogenetic tree of the AlaAT enzyme family. Comparison was performed using coding sequences of wheat and all fully sequenced for AlaAT genes in Arabidopsis by Clustal W2
© Copyright Policy
Related In: Results  -  Collection

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

Fig2: Sequence analysis of AlaAT homologues from wheat. a Alignment of obtained sequences by ClustalX 1.83. b Phylogenetic tree of the AlaAT enzyme family. Comparison was performed using coding sequences of wheat and all fully sequenced for AlaAT genes in Arabidopsis by Clustal W2
Mentions: From the wheat genome sequencing information available in the public data domain (TIGR, http://compbio.dfci.harvard.edu/cgi-bin/tgi/gimain.pl?gudb=wheat) it was searched for the the presence of AlaAT isoenzymes using the tBLASTn. Four fragments of cDNA encoding wheat AlaATs corresponding to Arabidopsis genes (At1g72330, At1g17290, At1g23310, At1g70580) were obtained (Fig. 2a). A phylogenetic analysis of AlaAT from Arabidopsisthaliana and Triticum aestivum performed using ClustalW programme (Higgins et al. 1994) showed that two of them were closely related to Arabidopsis AlaAT1 and AlaAT2 while other two appeared to be related to GGAT1 and GGAT2 (Fig. 2b).Fig. 2

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