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Glutaminase activity of PDX2. A, Initial rates of PDX2 glutaminase activity either in the absence of PDX1 (dashed and dotted line) or in the presence of PDX1.1 (solid line), PDX1.2 (dotted line), or PDX1.3 (dashed line). In every case, 10 mM of each protein and 20 mM Gln was used. B, Rate of PDX2 (10 mM) glutaminase activity as a function of the concentration of PDX1.1 (molar ratio 0-3.0).
Source publication
Vitamin B6 is an essential metabolite in all organisms, being required as a cofactor for a wide variety of biochemical reactions. De novo biosynthesis of the vitamin occurs in microorganisms and plants, but animals must obtain it from their diet. Two distinct and mutually exclusive de novo pathways have been identified to date, namely deoxyxylulose...
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Context 1
... certain lower organisms, PDX2 has been identi- fied as the glutaminase domain of the Gln amido- transferase, PLP synthase (Belitsky, 2004;Dong et al., 2004;Gengenbacher et al., 2006). Here, we have established functionality of the plant protein by dem- onstrating glutaminase activity of the isolated recom- binant protein (Fig. 3). Activity as a function of the Gln concentration followed typical Michaelis-Menten ki- netics from which the catalytic constants could be estimated (turnover number [k cat ] 5 0.23 6 0.01 min 21 and K m 5 1.92 6 0.32 mM; Supplemental Fig. S1). While the K m is within the range of those observed with the orthologous B. subtilis ( ...
Context 2
... in contrast to what has been observed previously with the bacterial and apicomplexan proteins ( Raschle et al., 2005;Gengenbacher et al., 2006), we could detect a basal glutaminase activity of the plant PDX2 in the absence of its partner protein PDX1 (0.04 min 21 ); in the presence of PDX1, the PDX2 activity increased ap- proximately 4-fold (Fig. 3A). The level of activity was not appreciably different with either PDX1.1 or PDX1.3, whereas PDX1.2 did not significantly enhance the glutaminase activity of PDX2 (Fig. 3A). Optimal activity was observed when the functional PDX pro- teins were in a 1:1 molar ratio, indicating a stoichio- metric protein complex (Fig. ...
Context 3
... glutaminase activity of the plant PDX2 in the absence of its partner protein PDX1 (0.04 min 21 ); in the presence of PDX1, the PDX2 activity increased ap- proximately 4-fold (Fig. 3A). The level of activity was not appreciably different with either PDX1.1 or PDX1.3, whereas PDX1.2 did not significantly enhance the glutaminase activity of PDX2 (Fig. 3A). Optimal activity was observed when the functional PDX pro- teins were in a 1:1 molar ratio, indicating a stoichio- metric protein complex (Fig. ...
Context 4
... ap- proximately 4-fold (Fig. 3A). The level of activity was not appreciably different with either PDX1.1 or PDX1.3, whereas PDX1.2 did not significantly enhance the glutaminase activity of PDX2 (Fig. 3A). Optimal activity was observed when the functional PDX pro- teins were in a 1:1 molar ratio, indicating a stoichio- metric protein complex (Fig. ...
Context 5
... predominant than either PDX1.1 or PDX1.3, e.g. roots and etiolated seedlings (Supplemental Fig. S3). Data provided by Genevestigator ( Zimmermann et al., 2004) support a high correlation between PDX2, PDX1.1, and PDX1.3 but very weak correlation with PDX1.2 (Supplemental Fig. S4). In contrast to certain other metabolic mutations that can be successfully res- cued in a relatively straightforward manner by addi- tion of the missing ...
Similar publications
Pyridoxal 5'-phosphate (PLP, vitamin B6), a cofactor in many enzymatic reactions, has two distinct biosynthetic routes, which do not coexist in any organism. Two proteins, known as PdxS and PdxT, together form a PLP synthase in plants, fungi, archaea, and some eubacteria. PLP synthase is a heteromeric glutamine amidotransferase in which PdxT produc...
Citations
... Pyridoxal 5′ phosphate produced can then be converted into other forms via salvage pathway present in all living organisms (Colinas et al. 2016). Both enzyme, PDX1 and PDX2, are critical for plant growth and development as demonstrated by previous research (Raschke et al. 2011;Tambasco-Studart et al. 2007). Several transgenic plants have been developed using both PDX1 and PDX2 genes (Bagri et al. 2018;Chen and Xiong 2009;Herrero and Daub 2007;Mangel et al. 2019). ...
... This could have been due to strict homeostatic mechanism for the de novo pathway (Herrero and Daub 2007). The discrepancy between the mRNA and protein levels could have also been due to various post-translational factors such as concentration of free and total ribosomes or mRNA levels, fluctuations in initiation and elongation kinetics due to competition for aminoacyl tRNAs, changes in termination kinetics, and changes in protein stability (Mehra et al. 2003;Mohsin et al. 2017;Tambasco-Studart et al. 2007). Various factors like the position of transgene insertion, copy number, and stage of seed at the time of RNA extraction could have also contributed to such results. ...
... Moreover, the carbohydrates like glucose, maltose, pyruvate, and sucrose are also altered by modification in gene expressions of de novo pathway genes (Parra et al. 2018;Raschke et al. 2011). The point of transgene insertion could have affected the expression level and thus not all transgenics showed the same trend (Tambasco-Studart et al. 2007). Moreover, the differences in values of the parameters studied among the varieties might be due to difference in the genotype of the two varieties (Ali et al. 2007). ...
Vitamin B6 is an essential micronutrient for humans which is synthesized in plants via de novo pathway. Since this pathway involves only two enzymes, it can be easily exploited to develop biofortified crops. In the present study, we investigated the effect of overexpressing PDX2 gene from Arabidopsis under endosperm-specific promoter for enhancing B6 levels in wheat seeds. Calli of two elite wheat varieties, Faisalabad-2008 and Galaxy, were transformed with PDX2 construct in expression vector via Agrobacterium-mediated transformation with the efficiency of 2.11% and 1.09%, respectively. Among the ten transgenic lines evaluated, the highest gene expression observed was 22.49-fold leading to 6.49-fold increase in B6 accumulation in mature seeds determined via HPLC. Vitamin B6 accumulation did not alter the chlorophyll content. However, the soluble protein content significantly decreased in some transgenic lines as compared to control plants. Some Faisalabad-2008 transgenic lines exhibited significant increase while all Galaxy transgenic lines showed significant decrease in their carbohydrate content than control plants. Moreover, seed yield increased in some transgenic lines without posing any variation in other agro-economically important traits. Previously vitamin B6 accumulation has been reported to confer resistance to abiotic factors because of its antioxidant properties. However, the transgene expression and vitamin B6 accumulation in the seed did not confer salt resistance to the transgenic lines. The amount of proline increased in salt-stressed plants while chlorophyll, protein, carbohydrate, and relative water content decreased. Thus, overexpression of PDX2 under seed-specific promoter enhances accumulation of vitamin B6 without conferring any resistance to salt stress conditions.
... In this study, after waterlogging stress, vitamin B6 metabolic pathways were more significantly enriched in waterlogging-tolerant rapeseed G230, and some genes and metabolites were significantly changed. The de novo synthesis of vitamin B6 in plants relies on two proteins, PDX1 and PDX2, which function as transglutaminase enzymes and produce pyridoxal phosphate (PLP) from glycolytic intermediates and the pentose phosphate pathway [44,45] (Figure 9A). We found that the PDX2 gene was significantly up-regulated in G218 root tissue, G230 root tissue, and leaf tissue after waterlogging stress. ...
During the growth period of rapeseed, if there is continuous rainfall, it will easily lead to waterlogging stress, which will seriously affect the growth of rapeseed. Currently, the mechanisms of rapeseed resistance to waterlogging stress are largely unknown. In this study, the rapeseed (Brassica napus) inbred lines G230 and G218 were identified as waterlogging-tolerant rapeseed and waterlogging-sensitive rapeseed, respectively, through a potted waterlogging stress simulation and field waterlogging stress experiments. After six days of waterlogging stress at the seedling stage, the degree of leaf aging and root damage of the waterlogging-tolerant rapeseed G230 were lower than those of the waterlogging-sensitive rapeseed G218. A physiological analysis showed that waterlogging stress significantly increased the contents of malondialdehyde, soluble sugar, and hydrogen peroxide in rape leaves and roots. The transcriptomic and metabolomic analysis showed that the differential genes and the differential metabolites of waterlogging-tolerant rapeseed G230 were mainly enriched in the metabolic pathways, biosynthesis of secondary metabolites, flavonoid biosynthesis, and vitamin B6 metabolism. Compared to G218, the expression levels of some genes associated with flavonoid biosynthesis and vitamin B metabolism were higher in G230, such as CHI, DRF, LDOX, PDX1.1, and PDX2. Furthermore, some metabolites involved in flavonoid biosynthesis and vitamin B6 metabolism, such as naringenin and epiafzelechin, were significantly up-regulated in leaves of G230, while pyridoxine phosphate was only significantly down-regulated in roots and leaves of G218. Furthermore, foliar spraying of vitamin B6 can effectively improve the tolerance to waterlogging of G218 in the short term. These results indicate that flavonoid biosynthesis and vitamin B6 metabolism pathways play a key role in the waterlogging tolerance and hypoxia stress resistance of Brassica napus and provide new insights for improving the waterlogging tolerance and cultivating waterlogging-tolerant rapeseed varieties.
... GG from different sources such as Gram-positive and Gramnegative bacteria (including extremophiles), actinomycetes, yeast, filamentous fungi, plants and mammals have been purified and characterized, displaying a wide range of properties (Tambasco-Studart et al. 2007;Cassago et al. 2012;Binod et al. 2017;Amobonye et al. 2019). Characteristics such as thermal stability, resistance to proteases and catalytic efficiency at high salt concentrations have been investigated by several works, given that these properties would be compatible with processes widely used by the food industry such as heating and fermentation (Moriguchi et al. 1994;Wakayama et al. 2005;Kumar et al. 2012;Ye et al. 2013;Mosallatpour et al. 2019). ...
l-Glutaminases are enzymes that catalyze the cleavage of the gamma-amido bond of l-glutamine residues, producing ammonia and l-glutamate. These enzymes have several applications in food and pharmaceutical industries. However, the l-glutaminases that hydrolyze free l-glutamine (l-glutamine glutaminases, EC 3.5.1.2) have different structures and properties with respect to the l-glutaminases that hydrolyze the same amino acid covalently bound in peptides (peptidyl glutaminases, EC 3.5.1.43) and proteins (protein-glutamine glutaminase, EC 3.5.1.44). In the food industry, l-glutamine glutaminases are applied to enhance the flavor of foods, whereas protein glutaminases are useful to improve the functional properties of proteins. This review will focus on structural backgrounds and differences between these enzymes, the methodology available to measure the activity as well as strengths and limitations. Production methods, applications, and challenges in the food industry will be also discussed. This review will provide useful information to search and identify the suitable l-glutaminase that best fits to the intended application.
... Further analysis indicated that among the above expanded gene families, a total of 148 genes encoding pyridoxal 5′-phosphate synthase were identified in P. mira and the corresponding gene numbers decreased to 6, 19, and 92 in P. davidiana, P. kansuensis, and P. ferganensis, respectively. Enzyme encoded by this gene family catalyzes the hydrolysis of glutamine to glutamate and ammonia as part of the biosynthesis of pyridoxal 5'-phosphate [36]. It was reported that pyridoxal 5'-phosphate was an essential compound to improve saltstress tolerance in Arabidopsis [37], wheat [38] and rice [39]. ...
Background
Peach (Prunus persica) is an economically important stone fruit crop in Rosaceae and widely cultivated in temperate and subtropical regions, emerging as an excellent material to study the interaction between plant and environment. During its genus, there are four wild species of peach, all living in harsh environments. For example, one of the wild species, P. mira, originates from the Qinghai-Tibet Plateau (QTP) and exhibits strong cold/ultraviolet ray environmental adaptations. Although remarkable progresses in the gene discovery of fruit quality-related traits in peach using previous assembled genome were obtained, genomic basis of the response of these wild species to different geographical environments remains unclear.
Results
To uncover key genes regulating adaptability in different species and analyze the role of genetic variations in resistance formation, we performed de novo genome assembling of four wild relatives of peach (P. persica), P. mira, P. davidiana, P. kansuensis, and P. ferganensis and resequenced 175 peach varieties. The phylogenetic tree showed that the divergence time of P. mira and other wild relatives of peach was 11.5 million years ago, which was consistent with the drastic crustal movement of QTP. Abundant genetic variations were identified in four wild species when compared to P. persica, and the results showed that plant-pathogen interaction pathways were enriched in genes containing small insertions and deletions and copy number variations in all four wild relatives of peach. Then, the data were used to identify new genes and variations regulating resistance. For example, presence/absence variations which result from a hybridization event that occurred between P. mira and P. dulcis enhanced the resistance of their putative hybrid, P. davidiana. Using bulked segregant analysis, we located the nematode resistance locus of P. kansuensis in chromosome 2. Within the mapping region, a deletion in the promoter of one NBS-LRR gene was found to involve the resistance by regulating gene expression. Furthermore, combined with RNA-seq and selective sweeps analysis, we proposed that a deletion in the promoter of one CBF gene was essential for high-altitude adaptation of P. mira through increasing its resistance to low temperature.
Conclusions
In general, the reference genomes assembled in the study facilitate our understanding of resistance mechanism of perennial fruit crops, and provide valuable resources for future breeding and improvement.
... FVEG_06020 encodes a homolog of PDX2, a glutamine amidotransferase, and FVEG_06021 encodes a homolog of PDX1, a pyridoxal-5'-phosphate (PLP) synthase. These are the core enzymes for biosynthesis of pyridoxine (Titiz et al., 2006;Tambasco-Studart et al., 2007). Lastly, FVEG_06024 putatively encodes the PLP-dependent 1-aminocyclopropane-1carboxylate deaminase, which hydrolyzes 1-aminocyclopropane -1-carboxylate (ACC) to ammonia and alpha-ketobutyrate (Van de Poel and van der Straeten, 2014). ...
The important cereal crops of maize, rye, and wheat constitutively produce precursors to 2-benzoxazolinone, a phytochemical having antifungal effects towards many Fusarium species. However, Fusarium verticillioides can tolerate 2-benzoxazolinone by converting it into non-toxic metabolites through the synergism of two previously identified gene clusters, FDB1 and FDB2. Inspired by the induction of these two clusters upon exposure to 2-benzoxazolinone, RNA sequencing experiments were carried out by challenging F. verticillioides individually with 2-benzoxazolinone and three related chemical compounds, 2-oxindole, 2-coumaranone, and chlorzoxazone. These compounds all contain lactam and/or lactone moieties, and transcriptional analysis provided inferences regarding the degradation of such lactams and lactones. Besides induction of FDB1 and FDB2 gene clusters, four additional clusters were identified as induced by 2-benzoxazolinone exposure, including a cluster thought to be responsible for biosynthesis of pyridoxine (vitamin B6), a known antioxidant providing tolerance to reactive oxygen species. Three putative gene clusters were identified as induced by challenging F. verticillioides with 2-oxindole, two with 2-coumaranone, and two with chlorzoxazone. Interestingly, 2-benzoxazolinone and 2-oxindole each induced two specific gene clusters with similar composition of enzymatic functions. Exposure to 2-coumranone elicited the expression of the fusaric acid biosynthetic gene cluster. Another gene cluster that may encode enzymes responsible for degrading intermediate catabolic metabolites with carboxylic ester bonds was induced by 2-benzoxazolinone, 2-oxindole, and chlorzoxazone. Also, the induction of a dehalogenase encoding gene during chlorzoxazone exposure suggested its role in the removal of the chlorine atom. Together, this work identifies genes and putative gene clusters responsive to the 2-benzoxazolinone-like compounds with metabolic inferences. Potential targets for future functional analyses are discussed.
... Theanine hydrolase activity was detected not only in tea plants but also in Arabidopsis and tomato (Solanum lycopersicum) [49,52,53]. Arabidopsis Pyridoxine Biosynthesis 2 (AtPDX2) has glutaminase activity to hydrolyze Gln to ammonia and Glu [54]. Fu et al. [40] cloned CsPDX2.1, the homolog of AtPDX2, and showed that the recombinant CsPDX2.1 had theanine hydrolase activity in vitro. ...
Theanine, a tea plant-specific non-proteinogenic amino acid, is the most abundant free amino acid in tea leaves. It is also one of the most important quality components of tea because it endows the "umami" taste, relaxation-promoting, and many other health benefits of tea infusion. Its content in tea leaves is directly correlated with the quality and price of green tea. Theanine biosynthesis primarily occurs in roots and is transported to new shoots in tea plants. Recently, great advances have been made in theanine metabolism and transport in tea plants. Along with the deciphering of the genomic sequences of tea plants, new genes in theanine metabolic pathway were discovered and functionally characterized. Theanine transporters were identified and were characterized on the affinity for: theanine, substrate specificity, spatiotemporal expression, and the role in theanine root-to-shoot transport. The mechanisms underlying the regulation of theanine accumulation by: cultivars, seasons, nutrients, and environmental factors are also being rapidly uncovered. Transcription factors were identified to be critical regulators of theanine biosynthesis. In this review, we summarize the progresses in theanine: biosynthesis, catabolism, and transport processes. We also discuss the future studies on theanine in tea plants, and application of the knowledge to crops to synthesize theanine to improve the health-promoting quality of non-tea crops.
... Two prevalent vitamin biosynthesis-related proteins, viz., riboflavin biosynthesis protein RIBA 3 (Q6L506) and pyridoxal 5 0 -phosphate synthase (A0A0P0XTG9) were observed to be in lower abundance in non-inoculated rice plants under salt-stress conditions. Vitamins are important for plant growth and development and are essential for transferring excitation energy to chlorophyll for efficient photosynthesis (Titiz et al., 2006;Tambasco-Studart et al., 2007;Cupellini et al., 2020). However, salt stress reduces the vitamin content in plants which can affect the photosynthetic efficiency and decrease plant biomass (Nan et al., 2020). ...
The omics-based studies are important for identifying characteristic proteins in plants to elucidate the mechanism of ACC deaminase producing bacteria-mediated salt tolerance. This study evaluates the changes in the proteome of rice inoculated with ACC deaminase producing bacteria under salt stress conditions. Salt stress resulted in a significant decrease in photosynthetic pigments, whereas inoculation of Methylobacterium oryzae CBMB20 had significantly increased pigment contents under normal and salt stress conditions. A total of 76, 51 and 33 differentially abundant proteins (DAPs) were identified in non-inoculated salt stressed plants, bacteria inoculated plants under normal and salt stress conditions, respectively. The abundances of proteins responsible for ethylene emission and programmed cell death were increased, and that of photosynthesis-related proteins were decreased in non-inoculated plants under salt stress. Whereas, bacteria-inoculated plants had shown higher abundance of antioxidant proteins, RuBisCo and ribosomal proteins that are important for enhancing stress tolerance and improving plant physiological traits. Collectively, salt stress might affect plant physiological traits by impairing photosynthetic machinery and accelerating apoptosis leading to a decline in biomass. However, inoculation of plants with bacteria can assist in enhancing photosynthetic activity, antioxidant activities and ethylene regulation related proteins for attenuating salt induced apoptosis and sustaining growth and development.
... Transcriptome sequencing indicated that the VitB6 biosynthesis pathway was involved in the response of Lilium pumilum to Fusarium oxysporum . Two protein families, PDX1s and PDX2, were required for the de novo biosynthesis of VitB6 (Tambasco-Studart et al., 2007). In this investigation, the VitB6 metabolism pathway was found to contribute to the resistance of poplars to pathogen infection. ...
... Similarly, the VitB6 metabolism pathway was activated by PDX. CDPK and PDX may regulate a burst of reactive oxygen species (ROS), leading to the hypersensitive response (HR) (Tambasco-Studart et al., 2007). Appropriate activation of HR by pathogens may cause, or have an association with, plant disease resistance (Balint-Kurti, 2019). ...
DNA methylation plays crucial roles in responses to environmental stimuli. Modification of DNA methylation during development and abiotic stress responses has been confirmed in increasing numbers of plants, mainly annual plants. However, the epigenetic regulation mechanism underlying the immune response to pathogens remains largely unknown in plants, especially trees. To investigate whether DNA methylation is involved in the response to infection process or is related to the resistance differences among poplars, we performed comprehensive whole-genome bisulfite sequencing of the infected stem of the susceptible type Populus × euramerican ‘74/76’ and resistant type Populus tomentosa ‘henan’ upon Lonsdalea populi infection. The results revealed that DNA methylation changed dynamically in poplars during the infection process with a remarkable decrease seen in the DNA methylation ratio. Intriguingly, the resistant P. tomentosa ‘henan’ had a much lower basal DNA methylation ratio than the susceptible P. × euramerican ‘74/76’. Compared to mock-inoculation, both poplar types underwent post-inoculation CHH hypomethylation; however, significant decreases in mC and mCHH proportions were found in resistant poplar. In addition, most differentially CHH-hypomethylated regions were distributed in repeat and promoter regions. Based on comparison of DNA methylation modification with the expression profiles of genes, DNA methylation occurred in resistance genes, pathogenesis-related genes, and phytohormone genes in poplars during pathogen infection. Additionally, transcript levels of genes encoding methylation-related enzymes changed during pathogen infection. Interestingly, small-regulator miRNAs were subject to DNA methylation in poplars experiencing pathogen infection. This investigation highlights the critical role of DNA methylation in the poplar immune response to pathogen infection and provides new insights into epigenetic regulation in perennial plants in response to biotic stress.
... superfamily, for example, a PLP synthase in Arabidopsis is reported to have a GATase domain (PDX2) and a synthase domain (PDX1) and is involved in biosynthesis of vitamin B6 in plants [10]. The NH 3 produced by hydrolysis of Gln via the PDX2 domain is tunnelled to the PDX1 domain which catalyses the formation of PLP (vitamin B6) using ribulose 5-phosphate or a combination of ribulose 5-phosphate and glyceraldehyde 3-phosphate [10]. ...
... superfamily, for example, a PLP synthase in Arabidopsis is reported to have a GATase domain (PDX2) and a synthase domain (PDX1) and is involved in biosynthesis of vitamin B6 in plants [10]. The NH 3 produced by hydrolysis of Gln via the PDX2 domain is tunnelled to the PDX1 domain which catalyses the formation of PLP (vitamin B6) using ribulose 5-phosphate or a combination of ribulose 5-phosphate and glyceraldehyde 3-phosphate [10]. To date, two classes of GATases were identified, one that uses a Cys-His-Glu catalytic triad (Class I) for release of NH 3 , and the other that uses an N-terminal Cys residue (Class II). ...
The glutamine amidotransferase gene GAT1_2.1 is a marker of N status in Arabidopsis root, linked to a shoot branching phenotype. The protein has an N-terminal glutamine amidotransferase domain and a C-terminal extension with no recognizable protein domain. A purified, recombinant version of the glutamine amidotransferase domain was catalytically active as a glutaminase, with apparent Km value of 0.66 mM and Vmax value of 2.6 µkatal per mg. This form complemented an E. coli glutaminase mutant, ΔYneH. Spiking of root metabolite extracts with either the N-terminal or full length form purified from transformed tobacco leaves led to reciprocal changes in glutamine and ammonia concentration. No product derived from amido-¹⁵N-labeled glutamine was identified. Visualization of GAT1_2.1-YPF transiently expressed in tobacco leaves confirmed its mitochondrial localization. gat1_2.1 exhibited reduced growth as compared with wild-type seedlings on media with glutamine as sole nitrogen source. Results of targeted metabolite profiling pointed to a possible activation of the GABA shunt in the mutant following glutamine treatments, with reduced levels of glutamic acid, 2-oxoglutarate and γ-aminobutyric acid and increased levels of succinic acid. GAT1_2.1 may act as a glutaminase, in concert with Glutamate Dehydrogenase 2, to hydrolyze glutamine and channel 2-oxoglutarate to the TCA cycle under high nitrogen conditions.
... Vitamin B6 has been shown to be an efficient reactive oxygen species quencher in vitro and is considered to act in the same capacity in vivo (Wagner 2006). Most notable among which is the cofactor pyridoxal 5 0 -phosphate (PLP) (Tambasco-Studart et al. 2007). PLP, the most important vitamin in biology which serves as the cofactor of many enzymes. ...
... PLP, the most important vitamin in biology which serves as the cofactor of many enzymes. And PLP played an important role in amino acid metabolism (Tambasco-Studart et al. 2007). In the present study, two significantly DEPs were found to be involved in Vitamin B6 metabolism, including pyridoxal 5 0 -phosphate synthase pdxT subunit (PdxT) and pyridoxal 5 0 -phosphate synthase pdxS subunit (PdxS). ...
Ammonium (NH4⁺) is a major nitrogen source for tea plant growth. Although NH4⁺-induced growth of tea plants were reported, it was still unclear to elucidate the mechanism of proteins in tea plants in responding to NH4⁺ resupply. In the present study, the proteomic profiles of tea leaves under N deficiency/resupply were investigated by using LC-MS/MS and PRM technique. Compared with N deficiency, there were 247 and 328 proteins significantly expressed after 3 h and 3d of N resupplied, respectively. And compared with 3 h of N resupplied, there were 186 proteins significantly expressed after 3d of N resupplied. According to bioinformatics analysis, the results showed that different expressed proteins participated in various biological processes, such as PsbO, Pbs27, PsaN, and PsaF were involved in photosynthesis, ADH1, AOC3, URE, GDH1-2, and argD were involved in amino acid metabolism, CHI and ANR were involved in flavonoid biosynthesis, GSTF9, APX, and GSS were involved in glutathione metabolism, and PdxT and PdxS were involved in vitamin B6 metabolism. Through PPI analysis, the results showed that the interactions between different expressed proteins mainly occurred in the photosynthetic pathway. Ammonium supply has a profound impact on photosynthesis, amino acid metabolism, flavonoid biosynthesis, glutathione metabolism, and vitamin B6 metabolism.
