Differential subcellular localization, enzymatic properties and expression patterns of γ-aminobutyric acid transaminases (GABA-Ts) in rice (Oryza sativa)

Shimajiri, Yasuka; Ozaki, Kae; Kainou, Kumiko; Akama, Kiyoshi

doi:10.1016/j.jplph.2012.09.007

Cited by 25 publications

(24 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To increase GAD activity in seeds, we successfully established a truncated version of GAD2 that induced higher accumulation of GABA (Akama et al ., ). For the knockdown of GABA‐Ts, we explored mRNA expression levels of four different rice GABA‐Ts (Shimajiri et al ., ): GABA‐T1 and T2 were relatively highly expressed, GABA‐T3 showed a low expression level but high enzymatic activity, and GABA‐T4 had negligible expression in seed maturation, so we chose GABA‐T1, T2, and T3 as targets. Approximately 100–200 bp of trigger sequence was PCR amplified to create RNAi cassettes in reverse orientation at both ends of the linker sequence of the first intron sequence of the GABA‐T1 gene.…”

Section: Resultsmentioning

confidence: 99%

“…With regard to rice GABA‐Ts, there have been no reports on their contribution to GABA accumulation in rice. The rice GABA‐T family consists of four genes; GABA‐T1 and GABA‐T2 are highly expressed in seed maturation, whereas GABA‐T3 is expressed at a low level and that of GABA‐T4 is negligible (Shimajiri et al ., ). As far as we are aware, comprehensive investigation of metabolic reprogramming with this combination of overexpression and knockdown of the GABA shunt has not been performed previously.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Genetic manipulation of the γ‐aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of γ‐aminobutyric acid transaminase (GABA‐T) lead to sustained and high levels of GABA accumulation in rice kernels

Shimajiri

Oonishi

Ozaki

et al. 2013

Plant Biotechnology Journal

Self Cite

View full text Add to dashboard Cite

SummaryGamma-aminobutyric acid (GABA) is a non-protein amino acid commonly present in all organisms. Because cellular levels of GABA in plants are mainly regulated by synthesis (glutamate decarboxylase, GAD) and catabolism (GABA-transaminase, GABA-T), we attempted seed-specific manipulation of the GABA shunt to achieve stable GABA accumulation in rice. A truncated GAD2 sequence, one of five GAD genes, controlled by the glutelin (GluB-1) or rice embryo globulin promoters (REG) and GABA-T-based trigger sequences in RNA interference (RNAi) cassettes controlled by one of these promoters as well, was introduced into rice (cv. Koshihikari) to establish stable transgenic lines under herbicide selection using pyriminobac. T 1 and T 2 generations of rice lines displayed high GABA concentrations (2-100 mg/100 g grain). In analyses of two selected lines from the T 3 generation, there was a strong correlation between GABA level and the expression of truncated GAD2, whereas the inhibitory effect of GABA-T expression was relatively weak. In these two lines both with two T-DNA copies, their starch, amylose, and protein levels were slightly lower than non-transformed cv. Koshihikari. Free amino acid analysis of mature kernels of these lines demonstrated elevated levels of GABA (75-350 mg/ 100 g polished rice) and also high levels of several amino acids, such as Ala, Ser, and Val. Because these lines of seeds could sustain their GABA content after harvest (up to 6 months), the strategy in this study could lead to the accumulation GABA and for these to be sustained in the edible parts.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Genetic manipulation of the γ‐aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of γ‐aminobutyric acid transaminase (GABA‐T) lead to sustained and high levels of GABA accumulation in rice kernels

Shimajiri

Oonishi

Ozaki

et al. 2013

Plant Biotechnology Journal

Self Cite

View full text Add to dashboard Cite

show abstract

“…Depending on the enzyme's substrate specificity, the GABA-T enzyme can be divided into two types: the 2-OGdependent GABA-T (GABA-TK) and the pyruvatedependent GABA-T (GABA-TP). While GABA-TK uses 2-OG to generate Glu, the bispecific GABA-TP uses pyruvate to generate Ala or glyoxylate to generate Gly (Clark et al, 2009a(Clark et al, , 2009bShimajiri et al, 2013;Trobacher et al, 2013). Succinic-semialdehyde Figure 3.…”

Section: Discussionmentioning

confidence: 99%

Alternative Oxidase Isoforms Are Differentially Activated by Tricarboxylic Acid Cycle Intermediates

et al. 2017

View full text Add to dashboard Cite

The cyanide-insensitive alternative oxidase (AOX) is a non-proton-pumping ubiquinol oxidase that catalyzes the reduction of oxygen to water and is posttranslationally regulated by redox mechanisms and 2-oxo acids. Arabidopsis (Arabidopsis thaliana) possesses five AOX isoforms (AOX1A-AOX1D and AOX2). AOX1D expression is increased in aox1a knockout mutants from Arabidopsis (especially after restriction of the cytochrome c pathway) but cannot compensate for the lack of AOX1A, suggesting a difference in the regulation of these isoforms. Therefore, we analyzed the different AOX isoenzymes with the aim to identify differences in their posttranslational regulation. Seven tricarboxylic acid cycle intermediates (citrate, isocitrate, 2-oxoglutarate, succinate, fumarate, malate, and oxaloacetate) were tested for their influence on AOX1A, AOX1C, and AOX1D wild-type protein activity using a refined in vitro system. AOX1C is insensitive to all seven organic acids, AOX1A and AOX1D are both activated by 2-oxoglutarate, but only AOX1A is additionally activated by oxaloacetate. Furthermore, AOX isoforms cannot be transformed to mimic one another by substituting the variable cysteine residues at position III in the protein. In summary, we show that AOX isoforms from Arabidopsis are differentially fine-regulated by tricarboxylic acid cycle metabolites (most likely depending on the amino-terminal region around the highly conserved cysteine residues known to be involved in regulation by the 2-oxo acids pyruvate and glyoxylate) and propose that this is the main reason why they cannot functionally compensate for each other.

show abstract

“…Supplemental material may be found here: www.landesbioscience.com/journals/psb/article/24274 pyruvate and glyoxylate as amino group acceptor, [18][19][20] exemplify the potentially broad substrate range of this class of proteins.…”

Section: Supplemental Materialsmentioning

confidence: 99%

Fiat lux!

Renault¹

2013

Plant Signaling & Behavior

View full text Add to dashboard Cite

Gamma-aminobutyric acid (GABA), a four-carbon non-protein amino acid, has drawn much attention since its first identification over 60 y ago in potato tuber, 1 rat brain 2 and yeast extract. 3Subsequent investigations of GABA functions followed two main directions: signaling and metabolism. Signaling effects of GABA have been intensively tackled in mammalian models. It has been clearly established that GABA acts as a neurotransmitter 4 and impacts the central nervous system development. 5,6 In plants, early studies in the 70-80s reported rapid GABA accumulation in response to many environmental cues.7-10 Based on these observations, it has been hypothesized that GABA could participate in stress responses and tolerance. Nevertheless, for decades, GABA functions in plants remained elusive. Major progress came along with the genomic era and availability of the powerful embedded tools. Genetic analyses in Arabidopsis demonstrated that GABA acts as a signal molecule for pollen tube guidance and elongation.11,12 Alteration of tricarboxylic acid (TCA) cycle enzyme activities shed light on GABA metabolic function and stressed the tight connection between GABA and respiration. [13][14][15] The functional implication of GABA metabolism in Arabidopsis salt stress tolerance has recently been reported. 16,17 The GABA transaminase gaba-t/pop2-1 mutant root growth was shown hypersensitive to the ionic component of salt stress, 16 confirming the long-standing hypothesis of GABA involvement in plant stress response. Metabolic data revealed that GABA bridges amino and organic acids metabolisms in roots underThe non-protein amino acid γ-aminobutyric acid (GABA) accumulates in plants in response to a wide variety of environmental cues. Recent data point toward an involvement of GABA in tricarboxylic acid (TCA) cycle activity and respiration, especially in stressed roots. To gain further insights into potential GABA functions in plants, phylogenetic and bioinformatic approaches were undertaken. Phylogenetic reconstruction of the GABA transaminase (GABA-T) protein family revealed the monophyletic nature of plant GABA-Ts. However, this analysis also pointed to the common origin of several plant aminotransferases families, which were found more similar to plant GABA-Ts than yeast and human GABA-Ts. A computational analysis of AtGABA-T co-expressed genes was performed in roots and in stress conditions. This second approach uncovered a strong connection between GABA metabolism and glyoxylate cycle during stress. Both in silico analyses open new perspectives and hypotheses for GABA metabolic functions in plants. Keywords: GABA-T, evolution, glyoxylate cycle, lipids, respiration, root, stress saline conditions. 16,17 Moreover, a genome-wide transcriptional analysis indicated that central carbon metabolism is altered upon the loss of GABA metabolic function during salt stress. Indeed, genes involved in remobilization of carbon reserves (i.e., sucrose and starch) were found higher expressed in the gaba-t/pop2-1 mutant. Fiat lux!17 However, de...

show abstract

Differential subcellular localization, enzymatic properties and expression patterns of γ-aminobutyric acid transaminases (GABA-Ts) in rice (Oryza sativa)

Cited by 25 publications

References 37 publications

Genetic manipulation of the γ‐aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of γ‐aminobutyric acid transaminase (GABA‐T) lead to sustained and high levels of GABA accumulation in rice kernels

Genetic manipulation of the γ‐aminobutyric acid (GABA) shunt in rice: overexpression of truncated glutamate decarboxylase (GAD2) and knockdown of γ‐aminobutyric acid transaminase (GABA‐T) lead to sustained and high levels of GABA accumulation in rice kernels

Alternative Oxidase Isoforms Are Differentially Activated by Tricarboxylic Acid Cycle Intermediates

Fiat lux!

Contact Info

Product

Resources

About