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Menard BS, Benidickson KH, Raytek LM, Snedden WA, Plaxton WC. Heterologous expression and purification of glutamate decarboxylase-1 from the model plant Arabidopsis thaliana: characterization of the enzyme's in vitro truncation by thiol endopeptidase activity. Protein Expr Purif 2024:106612. [PMID: 39343154 DOI: 10.1016/j.pep.2024.106612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2024] [Revised: 09/11/2024] [Accepted: 09/24/2024] [Indexed: 10/01/2024]
Abstract
Plant glutamate decarboxylase (GAD) is a Ca2+-calmodulin (CaM) activated enzyme that produces γ-aminobutyrate (GABA) as the first committed step of the GABA shunt. Our prior research established that in vivo phosphorylation of AtGAD1 (AT5G17330) occurs at multiple N-terminal serine residues following Pi resupply to Pi-starved cell cultures of the model plant Arabidopsis thaliana. The aim of the current investigation was to purify recombinant AtGAD1 (rAtGAD1) following its expression in Escherichia coli to facilitate studies of the impact of phosphorylation on its kinetic properties. However, in vitro proteolytic truncation of an approximate 5 kDa polypeptide from the C-terminus of 59 kDa rAtGAD1 subunits occurred during purification. Immunoblotting demonstrated that most protease inhibitors or cocktails that we tested were ineffective in suppressing this partial rAtGAD1 proteolysis. Although the thiol modifiers N-ethylmaleimide or 2,2-dipyridyl disulfide negated rAtGAD1 proteolysis, they also abolished its GAD activity. This indicates that an essential -SH group is needed for catalysis, and that rAtGAD1 is susceptible to partial degradation either by an E. coli cysteine endopeptidase, or possibly via autoproteolytic activity. The inclusion of exogenous Ca2+/CaM facilitated the purification of non-proteolyzed rAtGAD1 to a specific activity of 27 (μmol GABA produced/mg) at optimal pH 5.8, while exhibiting an approximate 3-fold activation by Ca2+/CaM at pH 7.3. By contrast, the purified partially proteolyzed rAtGAD1 was >40% less active at both pH values, and only activated 2-fold by Ca2+/CaM at pH 7.3. These results emphasize the need to diagnose and prevent partial proteolysis before conducting kinetic studies of purified regulatory enzymes.
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Affiliation(s)
| | | | - Lee Marie Raytek
- Dept. of Plant Sciences, McGill Univ., Ste-Anne-de-Bellevue, Quebec, Canada, H9X 3V9
| | - Wayne A Snedden
- Dept. of Biology, Queen's Univ., Kingston, Ontario, Canada, K7L 3N6
| | - William C Plaxton
- Dept. of Biology, Queen's Univ., Kingston, Ontario, Canada, K7L 3N6.
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Gerakari M, Kotsira V, Kapazoglou A, Tastsoglou S, Katsileros A, Chachalis D, Hatzigeorgiou AG, Tani E. Transcriptomic Approach for Investigation of Solanum spp. Resistance upon Early-Stage Broomrape Parasitism. Curr Issues Mol Biol 2024; 46:9047-9073. [PMID: 39194752 DOI: 10.3390/cimb46080535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2024] [Revised: 07/28/2024] [Accepted: 08/02/2024] [Indexed: 08/29/2024] Open
Abstract
Tomato (Solanum lycopersicum) is a major horticultural crop of high economic importance. Phelipanche and Orobanche genera (broomrapes) are parasitic weeds, constituting biotic stressors that impact tomato production. Developing varieties with tolerance to broomrapes has become imperative for sustainable agriculture. Solanum pennellii, a wild relative of cultivated tomato, has been utilized as breeding material for S. lycopersicum. In the present study, it is the first time that an in-depth analysis has been conducted for these two specific introgression lines (ILs), IL6-2 and IL6-3 (S. lycopersicum X S. pennellii), which were employed to identify genes and metabolic pathways associated with resistance against broomrape. Comparative transcriptomic analysis revealed a multitude of differentially expressed genes (DEGs) in roots, especially in the resistant genotype IL6-3, several of which were validated by quantitative PCR. DEG and pathway enrichment analysis (PEA) revealed diverse molecular mechanisms that can potentially be implicated in the host's defense response and the establishment of resistance. The identified DEGs were mostly up-regulated in response to broomrape parasitism and play crucial roles in various processes different from strigolactone regulation. Our findings indicate that, in addition to the essential role of strigolactone metabolism, multiple cellular processes may be involved in the tomato's response to broomrapes. The insights gained from this study will enhance our understanding and facilitate molecular breeding methods regarding broomrape parasitism. Moreover, they will assist in developing sustainable strategies and providing alternative solutions for weed management in tomatoes and other agronomically important crops.
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Affiliation(s)
- Maria Gerakari
- Laboratory of Plant Breeding and Biometry, Agricultural University of Athens, 11855 Athens, Greece
| | - Vasiliki Kotsira
- Hellenic Pasteur Institute, 11521 Athens, Greece
- DIANA-Lab, Department of Computer Science and Biomedical Informatics, University of Thessaly, 35131 Lamia, Greece
| | - Aliki Kapazoglou
- Hellenic Agricultural Organization-Dimitra (ELGO-DIMITRA), Department of Vitis, Institute of Olive Tree, Subtropical Crops and Viticulture (IOSV), Sofokli Venizelou 1, Lykovrysi, 14123 Athens, Greece
| | - Spyros Tastsoglou
- Hellenic Pasteur Institute, 11521 Athens, Greece
- DIANA-Lab, Department of Computer Science and Biomedical Informatics, University of Thessaly, 35131 Lamia, Greece
| | - Anastasios Katsileros
- Laboratory of Plant Breeding and Biometry, Agricultural University of Athens, 11855 Athens, Greece
| | - Demosthenis Chachalis
- Laboratory of Weed Science, Benaki Phytopathological Institute, 14561 Kifisia, Greece
| | - Artemis G Hatzigeorgiou
- Hellenic Pasteur Institute, 11521 Athens, Greece
- DIANA-Lab, Department of Computer Science and Biomedical Informatics, University of Thessaly, 35131 Lamia, Greece
| | - Eleni Tani
- Laboratory of Plant Breeding and Biometry, Agricultural University of Athens, 11855 Athens, Greece
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Benidickson KH, Raytek LM, Hoover GJ, Flaherty EJ, Shelp BJ, Snedden WA, Plaxton WC. Glutamate decarboxylase-1 is essential for efficient acclimation of Arabidopsis thaliana to nutritional phosphorus deprivation. THE NEW PHYTOLOGIST 2023; 240:2372-2385. [PMID: 37837235 DOI: 10.1111/nph.19300] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 09/15/2023] [Indexed: 10/15/2023]
Abstract
Glutamate decarboxylase (GAD) is a Ca2+ -calmodulin-activated, cytosolic enzyme that produces γ-aminobutyrate (GABA) as the committed step of the GABA shunt. This pathway bypasses the 2-oxoglutarate to succinate reactions of the tricarboxylic acid (TCA) cycle. GABA also accumulates during many plant stresses. We tested the hypothesis that AtGAD1 (At5G17330) facilitates Arabidopsis acclimation to Pi deprivation. Quantitative RT-PCR and immunoblotting revealed that AtGAD1 transcript and protein expression is primarily root-specific, but inducible at lower levels in shoots of Pi-deprived (-Pi) plants. Pi deprivation reduced levels of the 2-oxoglutarate dehydrogenase (2-OGDH) cofactor thiamine diphosphate (ThDP) in shoots and roots by > 50%. Growth of -Pi atgad1 T-DNA mutants was significantly attenuated relative to wild-type plants. This was accompanied by: (i) an > 60% increase in shoot and root GABA levels of -Pi wild-type, but not atgad1 plants, and (ii) markedly elevated anthocyanin and reduced free and total Pi levels in leaves of -Pi atgad1 plants. Treatment with 10 mM GABA reversed the deleterious development of -Pi atgad1 plants. Our results indicate that AtGAD1 mediates GABA shunt upregulation during Pi deprivation. This bypass is hypothesized to circumvent ThDP-limited 2-OGDH activity to facilitate TCA cycle flux and respiration by -Pi Arabidopsis.
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Affiliation(s)
| | - Lee Marie Raytek
- Department of Biology, Queen's University, Kingston, ON, K7L 3N6, Canada
| | - Gordon J Hoover
- Department of Plant Agriculture, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Edward J Flaherty
- Department of Plant Agriculture, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Barry J Shelp
- Department of Plant Agriculture, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Wayne A Snedden
- Department of Biology, Queen's University, Kingston, ON, K7L 3N6, Canada
| | - William C Plaxton
- Department of Biology, Queen's University, Kingston, ON, K7L 3N6, Canada
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Zhang M, Liu Z, Fan Y, Liu C, Wang H, Li Y, Xin Y, Gai Y, Ji X. Characterization of GABA-Transaminase Gene from Mulberry ( Morus multicaulis) and Its Role in Salt Stress Tolerance. Genes (Basel) 2022; 13:501. [PMID: 35328056 PMCID: PMC8954524 DOI: 10.3390/genes13030501] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Revised: 03/09/2022] [Accepted: 03/10/2022] [Indexed: 11/16/2022] Open
Abstract
Gamma-aminobutyric acid (GABA) has been reported to accumulate in plants when subjected to salt stress, and GABA-transaminase (GABA-T) is the main GABA-degrading enzyme in the GABA shunt pathway. So far, the salt tolerance mechanism of the GABA-T gene behind the GABA metabolism remains unclear. In this study, the cDNA (designated MuGABA-T) of GABA-T gene was cloned from mulberry, and our data showed that MuGABA-T protein shares some conserved characteristics with its homologs from several plant species. MuGABA-T gene was constitutively expressed at different levels in mulberry tissues, and was induced substantially by NaCl, ABA and SA. In addition, our results demonstrated that exogenous application of GABA significantly reduced the salt damage index and increased plant resistance to NaCl stress. We further performed a functional analysis of MuGABA-T gene and demonstrated that the content of GABA was reduced in the transgenic MuGABA-T Arabidopsis plants, which accumulated more ROS and exhibited more sensitivity to salt stress than wild-type plants. However, exogenous application of GABA significantly increased the activities of antioxidant enzymes and alleviated the active oxygen-related injury of the transgenic plants under NaCl stress. Moreover, the MuGABA-T gene was overexpressed in the mulberry hairy roots, and similar results were obtained for sensitivity to salt stress in the transgenic mulberry plants. Our results suggest that the MuGABA-T gene plays a pivotal role in GABA catabolism and is responsible for a decrease in salt tolerance, and it may be involved in the ROS pathway in the response to salt stress. Taken together, the information provided here is helpful for further analysis of the function of GABA-T genes, and may promote mulberry resistance breeding in the future.
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Affiliation(s)
- Mengru Zhang
- State Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China; (M.Z.); (Y.F.)
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Zhaoyang Liu
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Yiting Fan
- State Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China; (M.Z.); (Y.F.)
| | - Chaorui Liu
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Hairui Wang
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Yan Li
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Youchao Xin
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
| | - Yingping Gai
- State Key Laboratory of Crop Biology, Shandong Agricultural University, Taian 271018, China; (M.Z.); (Y.F.)
| | - Xianling Ji
- College of Forestry, Shandong Agricultural University, Taian 271018, China; (Z.L.); (C.L.); (H.W.); (Y.L.); (Y.X.)
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