Calmodulin binding to glutamate decarboxylase is required for regulation of glutamate and GABA metabolism and normal development in plants.

Baum, Gideon; Lev‐Yadun, Simcha; Fridmann, Yael; Arazi, Tzahi; Katsnelson, H; Zik, Moriyah; Fromm, Hillel

doi:10.1002/j.1460-2075.1996.tb00662.x

Cited by 261 publications

(170 citation statements)

References 52 publications

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“…We observed this phenotype in all the her1 alleles in the Col-0 background (her1-1, her1-2 and SALK7661), suggesting that the increased GABA levels are at the base of this alteration. This is further supported by the observation that tobacco plants, with increased GABA levels in the stem and leaves, show several developmental defects including increased branching (Baum et al, 1996). However, we observed no branching in pop2-1 and pop2-3 plants (in Ler and WS backgrounds, respectively).…”

Section: Interaction Of E-2-hexenal With Defense Signaling Pathwayssupporting

confidence: 87%

The Arabidopsis her1 mutant implicates GABA in E‐2‐hexenal responsiveness

Mirabella¹,

Rauwerda

Struys

et al. 2007

The Plant Journal

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SummaryWhen wounded or attacked by herbivores or pathogens, plants produce a blend of six-carbon alcohols, aldehydes and esters, known as C6-volatiles. Undamaged plants, when exposed to C6-volatiles, respond by inducing defense-related genes and secondary metabolites, suggesting that C6-volatiles can act as signaling molecules regulating plant defense responses. However, to date, the molecular mechanisms by which plants perceive and respond to these volatiles are unknown. To elucidate such mechanisms, we decided to isolate Arabidopsis thaliana mutants in which responses to C6-volatiles were altered. We observed that treatment of Arabidopsis seedlings with the C6-volatile E-2-hexenal inhibits root elongation. Among C6-volatiles this response is specific to E-2-hexenal, and is not dependent on ethylene, jasmonic and salicylic acid. Using this bioassay, we isolated 18 E-2-hexenal-response (her) mutants that showed sustained root growth after E-2-hexenal treatment. Here, we focused on the molecular characterization of one of these mutants, her1. Microarray and map-based cloning revealed that her1 encodes a c-amino butyric acid transaminase (GABA-TP), an enzyme that degrades GABA. As a consequence of the mutation, her1 plants accumulate high GABA levels in all their organs. Based on the observation that E-2-hexenal treatment induces GABA accumulation, and that high GABA levels confer resistance to E-2-hexenal, we propose a role for GABA in mediating E-2-hexenal responses.

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Section: Interaction Of E-2-hexenal With Defense Signaling Pathwayssupporting

confidence: 87%

The Arabidopsis her1 mutant implicates GABA in E‐2‐hexenal responsiveness

Mirabella¹,

Rauwerda

Struys

et al. 2007

The Plant Journal

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“…For example, it is known that Ca 2ϩ -CaM can induce dimerization of the plant enzyme glutamate decarboxylase (53,54). This dimerization process seems to be essential in plant development (55). Ca 2ϩ -CaM can also induce a dimer of NtMKP1 by binding to the NtMKP1pA region of another NtMKP1 through the N-lobe as has been discussed previously (Fig.…”

Section: Camentioning

confidence: 57%

Structural Studies of Soybean Calmodulin Isoform 4 Bound to the Calmodulin-binding Domain of Tobacco Mitogen-activated Protein Kinase Phosphatase-1 Provide Insights into a Sequential Target Binding Mode

Ishida

Rainaldi

Vogel

2009

Journal of Biological Chemistry

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The calcium regulatory protein calmodulin (CaM) binds in a calcium-dependent manner to numerous target proteins. The calmodulin-binding domain (CaMBD) region of Nicotiana tabacum MAPK phosphatase has an amino acid sequence that does not resemble the CaMBD of any other known Ca 2؉ -CaMbinding proteins. Using a unique fusion protein strategy, we have been able to obtain a high resolution solution structure of the complex of soybean Ca 2؉ -CaM4 (SCaM4) and this CaMBD. Complete isotope labeling of both parts of the complex in the fusion protein greatly facilitated the structure determination by NMR. The 12-residue CaMBD region was found to bind exclusively to the C-lobe of SCaM4. A specific Trp and Leu side chain are utilized to facilitate strong binding through a novel ''double anchor'' motif. Moreover, the orientation of the helical peptide on the surface of Ca 2؉ -SCaM4 is distinct from other known complexes. The N-lobe of Ca 2؉ -SCaM4 in the complex remains free for additional interactions and could possibly act as a calcium-dependent adapter protein.Signaling through the MAPK pathway and increases in intracellular Ca 2؉ are both hallmarks of the plant stress response, and our data support the notion that coordination of these responses may occur through the formation of a unique CaM-MAPK phosphatase multiprotein complex. Calmodulin (CaM)2 is a ubiquitous intracellular Ca 2ϩ sensor protein that plays an essential role in various Ca 2ϩ signaling pathways. Contiguous and unique CaM-binding domain (CaMBD) regions are found widely distributed in many different types of CaM target proteins including protein phosphatases and kinases, cytoskeletal proteins, ion channels, and pumps (1, 2). Even though the CaMBD from various proteins share relatively poor amino acid sequence similarity, the majority of CaMBD become ␣-helical upon binding to CaM, and they can be grouped into either the 1-5-10 or the 1-8-14 motif, where the first and the last number indicate the position of two hydrophobic anchor residues that attach the CaMBD to the two binding pockets of the bilobal Ca 2ϩ -CaM. However, several noncanonical classes of CaMBD have also been identified. For example, in the CaMBD of the MARCKS protein, the two anchor residues are separated by a single amino acid residue (3). On the other hand, in the recently determined crystal structure of Ca 2ϩ -CaM complexed with the CaMBD of the skeletal muscle ryanodine receptor RYR1, they are separated by 15 residues (1-17 motif) (4). Bulky hydrophobic side chains of residues such as Trp, Leu, Phe, and Ile are most commonly utilized as anchor residues (see Fig. 1a), and these are usually deeply inserted into the hydrophobic target-binding pocket of either the N-or C-lobe of Ca 2ϩ -CaM. However, in several cases, including the N-methyl-D-aspartate receptors (NMDAR) (5) and the voltage-gated Ca 2ϩ channels (Cav1-2) (6, 7), a polar side chain from Thr or Tyr has also been found to act as an anchor residue. In almost all Ca 2ϩ -CaM complexes studied to date, the two lobes of Ca 2ϩ -CaM bec...

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“…0.05) observed in leaves is probably due to the relatively low levels of labeled metabolites in this tissue. Tobacco leaves have very low levels of GDH transcript, protein, and activity compared with roots (Purnell et al, 2005) (Baum et al, 1996), the fact that [ 15 N]GABA accumulation in A63-NS leaves was only 7% of that in roots during the control treatment suggests that leaf [ 15 N]Glu concentration was relatively low. 1 within mesophyll cells (Keys et al, 1978).…”

Section: Gdh Isoenzyme 1 In Roots Catabolizes Glumentioning

confidence: 99%

Tobacco Isoenzyme 1 of NAD(H)-Dependent Glutamate Dehydrogenase Catabolizes Glutamate in Vivo

Purnell

Botella

2006

Plant Physiol.

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Glutamate (Glu) dehydrogenase (GDH, EC 1.4.1.2-1.4.1.4) catalyzes in vitro the reversible amination of 2-oxoglutarate to Glu. The in vivo direction(s) of the GDH reaction in higher plants and hence the role(s) of this enzyme is unclear, a situation confounded by the existence of isoenzymes comprised totally of either GDH b-(isoenzyme 1) or a-(isoenzyme 7) subunits, as well as another five a-b isoenzyme permutations. To clarify the in vivo direction of the reaction catalyzed by GDH isoenzyme 1, [ 15 N]Glu was supplied to roots of two independent transgenic tobacco (Nicotiana tabacum) lines with increased isoenzyme 1 levels (S4-H and S49-H). The [ 15 N]ammonium (NH 4 1 ) accumulation rate in these lines was elevated approximately 65% compared with a null segregant control line, indicating that isoenzyme 1 catabolizes Glu in roots. Leaf glutamine synthetase (GS) was inhibited with a GS-specific herbicide to quantify any contribution by GDH toward photorespiratory NH 4 1 reassimilation. Transgenic line S49-H did not show enhanced resistance to the herbicide, indicating that the large pool of isoenzyme 1 in S49-H leaves was unable to compensate for GS and suggesting that isoenzyme 1 does not assimilate NH 4 1 in vivo.The intricate linkage of plant C and N metabolism requires constant balancing at the cellular level. Fundamentally, this involves orchestrating cellular levels of three metabolites: ammonium (NH 4

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Calmodulin binding to glutamate decarboxylase is required for regulation of glutamate and GABA metabolism and normal development in plants.

Cited by 261 publications

References 52 publications

The Arabidopsis her1 mutant implicates GABA in E‐2‐hexenal responsiveness

The Arabidopsis her1 mutant implicates GABA in E‐2‐hexenal responsiveness

Structural Studies of Soybean Calmodulin Isoform 4 Bound to the Calmodulin-binding Domain of Tobacco Mitogen-activated Protein Kinase Phosphatase-1 Provide Insights into a Sequential Target Binding Mode

Tobacco Isoenzyme 1 of NAD(H)-Dependent Glutamate Dehydrogenase Catabolizes Glutamate in Vivo

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