Abstract
When subjected to low oxygen stress, plants accumulate alanine and gamma-aminobutyric acid (GABA). To investigate the function of GABA metabolism under hypoxia and its contribution to alanine accumulation, we studied the genes that encode the two key enzymes of the GABA shunt, glutamate decarboxylase (GAD) and GABA transaminase (GABA-T). Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs. Expression of the other three GAD genes was generally weak. In response to hypoxia, transcriptional induction was observed for GAD4 only. For GABA-T1, its expression was detected in all organs, but there was no significant transcriptional change under hypoxic conditions. Moreover, we have isolated and characterized Arabidopsis mutants defective in GAD1 and GABA-T1. In gad1 mutants, GAD activity was significantly reduced in roots but was not affected in shoots. In the gaba-t1 mutant, GABA-T activity was decreased to negligible levels in both shoots and roots. These mutants were phenotypically normal under normal growth conditions except for the reduced seed production of the pop2 mutants as described previously. However, metabolite analysis revealed significant changes in GABA content in gad1 and gaba-t1 mutants. The levels of alanine under hypoxic conditions were also affected in the roots of gad1 and gaba-t1 mutants. The partial inhibition of the hypoxia-induced alanine accumulation in roots of these mutants suggests that the GABA shunt is, in part, responsible for the alanine accumulation under hypoxia.
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Claims 13
Claim · model-written summary
GAD1 expression in Arabidopsis was predominantly found in roots.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Organ / stage
- rootse0
- Gene
- GAD1e0
- Outcome
- GAD1 expressione0
- Qualifier
- predominantlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
Claim · model-written summary
GAD2 expression in Arabidopsis was evident in all organs.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- all organse0
- Gene
- GAD2e0
- Outcome
- GAD2 expressione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
Claim · model-written summary
Expression of the other three GAD genes in Arabidopsis was generally weak.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Gene
- other three GAD genese1
- Outcome
- Expressione1
- Qualifier
- generally weake1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e1“Expression of the other three GAD genes was generally weak”
Claim · model-written summary
Under hypoxia, transcriptional induction of GAD4 was observed in Arabidopsis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- hypoxiae2
- Gene
- GAD4e2
- Outcome
- transcriptional inductione2
- Direction
- increaseinferrede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e2“In response to hypoxia, transcriptional induction was observed for GAD4 only”
Claim · model-written summary
GABA-T1 expression in Arabidopsis was detected in all organs.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- all organse3
- Gene
- GABA-T1e3
- Outcome
- its expressione3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e3“For GABA-T1, its expression was detected in all organs, but there was no significant transcriptional change under hypoxic conditions”
Claim · model-written summary
GABA-T1 showed no significant transcriptional change under hypoxic conditions in Arabidopsis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- hypoxic conditionse3
- Gene
- GABA-T1e3
- Outcome
- transcriptional changee3
- Direction
- no significante3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e3“For GABA-T1, its expression was detected in all organs, but there was no significant transcriptional change under hypoxic conditions”
Claim · model-written summary
In gad1 mutants, GAD activity was significantly reduced in roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- gad1 mutantse4
- Organ / stage
- rootse4
- Gene
- gad1e4
- Outcome
- GAD activitye4
- Direction
- significantly reducede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e4“In gad1 mutants, GAD activity was significantly reduced in roots but was not affected in shoots”
Claim · model-written summary
In gad1 mutants, GAD activity was not affected in shoots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- gad1 mutantse4
- Organ / stage
- shootse4
- Outcome
- GAD activitye4
- Direction
- not affectede4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e4“In gad1 mutants, GAD activity was significantly reduced in roots but was not affected in shoots”
Claim · model-written summary
In the gaba-t1 mutant, GABA-T activity was decreased to negligible levels in shoots and roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- gaba-t1 mutante5
- Organ / stage
- shoots and rootse5
- Gene
- GABA-Te5
- Outcome
- GABA-T activitye5
- Direction
- decreasede5
- Qualifier
- to negligible levelse5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e5“In the gaba-t1 mutant, GABA-T activity was decreased to negligible levels in both shoots and roots”
Claim · model-written summary
Mutant Arabidopsis plants were phenotypically normal under normal growth conditions.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Outcome
- phenotypically normale6
- Qualifier
- under normal growth conditionse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e6“These mutants were phenotypically normal under normal growth conditions”
Claim · model-written summary
GABA content changed significantly in gad1 and gaba-t1 mutants.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- gad1 and gaba-t1 mutantse7
- Outcome
- GABA contente7
- Direction
- changese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e7“metabolite analysis revealed significant changes in GABA content in gad1 and gaba-t1 mutants”
Claim · model-written summary
Under hypoxia, alanine levels in roots of gad1 and gaba-t1 mutants were affected.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Material
- gad1 and gaba-t1 mutantse1
- Organ / stage
- rootse1
- Treatment
- hypoxic conditionse1
- Outcome
- levels of alaninee1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e1“The levels of alanine under hypoxic conditions were also affected in the roots of gad1 and gaba-t1 mutants”
Claim · model-written summary
Partial inhibition of hypoxia-induced alanine accumulation in mutant roots suggests that the GABA shunt is partly responsible for alanine accumulation under hypoxia.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- hypoxiae1
- Outcome
- hypoxia-induced alanine accumulatione1
- Qualifier
- the GABA shunt is, in part, responsible for the alanine accumulation under hypoxiae1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among the five homologous GAD genes found in Arabidopsis thaliana, GAD1 expression was predominantly found in roots, while GAD2 expression was evident in all organs”
e1“The partial inhibition of the hypoxia-induced alanine accumulation in roots of these mutants suggests that the GABA shunt is, in part, responsible for the alanine accumulation under hypoxia”
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