Genome-Wide Analysis of Trehalose-6-Phosphate Phosphatase Gene Family and Their Expression Profiles in Response to Abiotic Stress in Groundnut

Trehalose-6-phosphate phosphatase (TPP) is a pivotal enzyme in trehalose biosynthesis which plays an essential role in plant development and in the abiotic stress response. However, little is currently known about TPPs in groundnut. In the present study, a total of 16 AhTPP genes were identified, and can be divided into three phylogenetic subgroups. AhTPP members within the same subgroups generally displayed similar exon-intron structures and conserved motifs. Gene collinearity analysis revealed that segmental duplication was the primary factor driving the expansion of the AhTPP family. An analysis of the upstream promoter region of AhTPPs revealed eight hormone- and four stress-related responsive cis-elements. Transcriptomic analysis indicated high expression levels of AhTPP genes in roots or flowers, while RT-qPCR analysis showed upregulation of the six tested genes under different abiotic stresses, suggesting that AhTPPs play roles in growth, development, and response to various abiotic stresses. Subcellular localization analysis showed that AhTPP1A and AhTPP5A were likely located in both the cytoplasm and the nucleus. To further confirm their functions, the genes AhTPP1A and AhTPP5A were individually integrated into yeast expression vectors. Subsequent experiments demonstrated that yeast cells overexpressing these genes displayed increased tolerance to osmotic and salt stress compared to the control group. This study will not only lay the foundation for further study of AhTPP gene functions, but will also provide valuable gene resources for improving abiotic stress tolerance in groundnut and other crops.

Validamycin Inhibits the Synthesis and Metabolism of Trehalose and Chitin in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a notorious invasive pest that has raised concerns worldwide. Validamycin has been demonstrated to be a very strong inhibitor against trehalase in a variety of organisms. However, whether validamycin can inhibit trehalase activity to suppress trehalose hydrolysis and affect any other relevant physiological pathways in B. dorsalis remains unknown. In this study, the effects of validamycin injection on the synthesis and metabolism of trehalose and chitin were evaluated. The results show that validamycin injection significantly affected trehalase activity and caused trehalose accumulation. In addition, the downstream pathways of trehalose hydrolysis, including the synthesis and metabolism of chitin, were also remarkably affected as the expressions of the key genes in these pathways were significantly regulated and the chitin contents were changed accordingly. Intriguingly, the upstream trehalose synthesis was also affected by validamycin injection due to the variations in the expression levels of key genes, especially BdTPPC1. Moreover, BdTPPC1 was predicted to have a binding affinity to validamycin, and the subsequent in vitro recombinant enzyme activity assay verified the inhibitory effect of validamycin on BdTPPC1 activity for the first time. These findings collectively indicate that validamycin can be considered as a promising potential insecticide for the management of B. dorsalis.

Trehalose-6-phosphate phosphatases are involved in trehalose synthesis and metamorphosis in Bactrocera minax

Trehalose is the principal sugar circulating in the hemolymph of insects, and trehalose synthesis is catalyzed by trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). Insect TPS is a fused enzyme containing both TPS domain and TPP domain. Thus, many insects do not possess TPP genes as TPSs have replaced the function of TPPs. However, TPPs are widely distributed across the dipteran insects, while the roles they play remain largely unknown. In this study, 3 TPP genes from notorious dipteran pest Bactrocera minax (BmiTPPB, BmiTPPC1, and BmiTPPC2) were identified and characterized. The different temporal-spatial expression patterns of 3 BmiTPPs implied that they exert different functions in B. minax. Recombinant BmiTPPs were heterologously expressed in yeast cells, and all purified proteins exhibited enzymatic activities, despite the remarkable disparity in performance between BmiTPPB and BmiTPPCs. RNA interference revealed that all BmiTPPs were successfully downregulated after double-stranded RNA injection, leading to decreased trehalose content and increased glucose content. Also, suppression of BmiTPPs significantly affected expression of downstream genes and increased the mortality and malformation rate. Collectively, these results indicated that all 3 BmiTPPs in B. minax are involved in trehalose synthesis and metamorphosis. Thus, these genes could be evaluated as insecticidal targets for managing B. minax, and even for other dipteran pests.

In Silico and Transcription Analysis of Trehalose-6-phosphate Phosphatase Gene Family of Wheat: Trehalose Synthesis Genes Contribute to Salinity, Drought Stress and Leaf Senescence

Trehalose-6-phosphate phosphatase (TPP) genes take part in trehalose metabolism and also in stress tolerance, which has been well documented in many species but poorly understood in wheat. The present research has identified a family of 31 TPP genes in Triticum aestivum L. through homology searches and classified them into five clades by phylogenetic tree analysis, providing evidence of an evolutionary status with Hordeum vulgare, Brachypodium distachyon and Oryza sativa. The exon-intron distribution revealed a discrete evolutionary history and projected possible gene duplication occurrences. Furthermore, different computational approaches were used to analyze the physical and chemical properties, conserved domains and motifs, subcellular and chromosomal localization, and three-dimensional (3-D) protein structures. Cis-regulatory elements (CREs) analysis predicted that TaTPP promoters consist of CREs related to plant growth and development, hormones, and stress. Transcriptional analysis revealed that the transcription levels of TaTPPs were variable in different developmental stages and organs. In addition, qRT-PCR analysis showed that different TaTPPs were induced under salt and drought stresses and during leaf senescence. Therefore, the findings of the present study give fundamental genomic information and possible biological functions of the TaTPP gene family in wheat and will provide the path for a better understanding of TaTPPs involvement in wheat developmental processes, stress tolerance, and leaf senescence.

Salt Stress Response of Sulfolobus acidocaldarius Involves Complex Trehalose Metabolism Utilizing a Novel Trehalose-6-Phosphate Synthase (TPS)/Trehalose-6-Phosphate Phosphatase (TPP) Pathway

The crenarchaeon Sulfolobus acidocaldarius has been described to synthesize trehalose via the maltooligosyltrehalose synthase (TreY) and maltooligosyltrehalose trehalohydrolase (TreZ) pathway, and the trehalose glycosyltransferring synthase (TreT) pathway has been predicted. Deletion mutant analysis of strains with single and double deletions of ΔtreY and ΔtreT in S. acidocaldarius revealed that in addition to these two pathways, a third, novel trehalose biosynthesis pathway is operative in vivo: the trehalose-6-phosphate (T6P) synthase/T6P phosphatase (TPS/TPP) pathway. In contrast to known TPS proteins, which belong to the GT20 family, the S. acidocaldarius TPS belongs to the GT4 family, establishing a new function within this group of enzymes. This novel GT4-like TPS was found to be present mainly in the Sulfolobales The ΔtreY ΔtreT Δtps triple mutant of S. acidocaldarius, which lacks the ability to synthesize trehalose, showed no altered phenotype under standard conditions or heat stress but was unable to grow under salt stress. Accordingly, in the wild-type strain, a significant increase of intracellular trehalose formation was observed under salt stress. Quantitative real-time PCR showed a salt stress-mediated induction of all three trehalose-synthesizing pathways. This demonstrates that in Archaea, trehalose plays an essential role for growth under high-salt conditions.IMPORTANCE The metabolism and function of trehalose as a compatible solute in Archaea was not well understood. This combined genetic and enzymatic approach at the interface of microbiology, physiology, and microbial ecology gives important insights into survival under stress, adaptation to extreme environments, and the role of compatible solutes in Archaea Here, we unraveled the complexity of trehalose metabolism, and we present a comprehensive study on trehalose function in stress response in S. acidocaldarius This sheds light on the general microbiology and the fascinating metabolic repertoire of Archaea, involving many novel biocatalysts, such as glycosyltransferases, with great potential in biotechnology.

Ectopic Expression of Jatropha curcas TREHALOSE-6-PHOSPHATE PHOSPHATASE J Causes Late-Flowering and Heterostylous Phenotypes in Arabidopsis but not in Jatropha

Trehalose-6-phosphate (T6P) phosphatase (TPP), a dephosphorylating enzyme, catalyzes the dephosphorylation of T6P, generating trehalose. In Jatropha, we found six members of the TPP family. Five of them JcTPPA, JcTPPC, JcTPPD, JcTPPG, and JcTPPJ are highly expressed in female flowers or male flowers, or both, suggesting that members of the JcTPP family may participate in flower development in Jatropha. The wide expression of JcTPPJ gene in various organs implied its versatile roles and thus was chosen for unraveling its biological functions during developmental process. We constructed an overexpression vector of JcTPPJ cDNA driven by the cauliflower mosaic virus (CaMV) 35S promoter for genetic transformation. Compared with control Arabidopsis plants, 35S:JcTPPJ transgenic Arabidopsis plants presented greater sucrose contents in their inflorescences and displayed late-flowering and heterostylous phenotypes. Exogenous application of sucrose to the inflorescence buds of wild-type Arabidopsis repressed the development of the perianth and filaments, with a phenocopy of the 35S:JcTPPJ transgenic Arabidopsis. These results suggested that the significantly increased sucrose level in the inflorescence caused (or induced) by JcTTPJ overexpression, was responsible for the formation of heterostylous flower phenotype. However, 35S:JcTPPJ transgenic Jatropha displayed no obvious phenotypic changes, implying that JcTPPJ alone may not be sufficient for regulating flower development in Jatropha. Our results are helpful for understanding the function of TPPs, which may regulate flower organ development by manipulating the sucrose status in plants.

Structures of trehalose-6-phosphate phosphatase from pathogenic fungi reveal the mechanisms of substrate recognition and catalysis

Trehalose is a disaccharide essential for the survival and virulence of pathogenic fungi. The biosynthesis of trehalose requires trehalose-6-phosphate synthase, Tps1, and trehalose-6-phosphate phosphatase, Tps2. Here, we report the structures of the N-terminal domain of Tps2 (Tps2NTD) from Candida albicans, a transition-state complex of the Tps2 C-terminal trehalose-6-phosphate phosphatase domain (Tps2PD) bound to BeF3 and trehalose, and catalytically dead Tps2PD(D24N) from Cryptococcus neoformans bound to trehalose-6-phosphate (T6P). The Tps2NTD closely resembles the structure of Tps1 but lacks any catalytic activity. The Tps2PD-BeF3-trehalose and Tps2PD(D24N)-T6P complex structures reveal a "closed" conformation that is effected by extensive interactions between each trehalose hydroxyl group and residues of the cap and core domains of the protein, thereby providing exquisite substrate specificity. Disruption of any of the direct substrate-protein residue interactions leads to significant or complete loss of phosphatase activity. Notably, the Tps2PD-BeF3-trehalose complex structure captures an aspartyl-BeF3 covalent adduct, which closely mimics the proposed aspartyl-phosphate intermediate of the phosphatase catalytic cycle. Structures of substrate-free Tps2PD reveal an "open" conformation whereby the cap and core domains separate and visualize the striking conformational changes effected by substrate binding and product release and the role of two hinge regions centered at approximately residues 102-103 and 184-188. Significantly, tps2Δ, tps2NTDΔ, and tps2D705N strains are unable to grow at elevated temperatures. Combined, these studies provide a deeper understanding of the substrate recognition and catalytic mechanism of Tps2 and provide a structural basis for the future design of novel antifungal compounds against a target found in three major fungal pathogens.

Contribution of trehalose biosynthetic pathway to drought stress tolerance of Capparis ovata Desf

Trehalose and the trehalose biosynthetic pathway are important contributors and regulators of stress responses in plants. Among recent findings for trehalose and its metabolism, the role of signalling in the regulation of growth and development and its potential for use as a storage energy source can be listed. The xerophytic plant Capparis ovata (caper) is well adapted to drought and high temperature stress in arid and semi-arid regions of the Mediterranean. The contribution of trehalose and the trehalose biosynthetic pathway to drought stress responses and tolerance in C. ovata are not known. We investigated the effects of PEG-mediated drought stress in caper plants and analysed physiological parameters and trehalose biosynthetic pathway components, trehalose-6-phosphate synthase (TPS), trehalose-6-phosphate phosphatase (TPP), trehalase activity, trehalose and proline content in drought stress-treated and untreated plants. Our results indicated that trehalose and the trehalose biosynthetic pathway contributed to drought stress tolerance of C. ovata. Overall growth and leaf water status were not dramatically affected by drought, as both high relative growth rate and relative water content were recorded even after 14 days of drought stress. Trehalose accumulation increased in parallel to induced TPS and TPP activities and decreased trehalase activity in caper plants on day 14. Constitutive trehalose levels were 28.75 to 74.75 μg·g·FW(-1) , and drought stress significantly induced trehalose accumulation (385.25 μg·g·FW(-1) on day 14) in leaves of caper. On day 14 of drought, proline levels were lower than on day 7. Under drought stress the discrepancy between trehalose and proline accumulation trends might result from the mode of action of these osmoprotectant molecules in C. ovata.

Fine tuning of trehalose biosynthesis and hydrolysis as novel tools for the generation of abiotic stress tolerant plants

The impact of abiotic stress on plant growth and development has been and still is a major research topic. An important pathway that has been linked to abiotic stress tolerance is the trehalose biosynthetic pathway. Recent findings showed that trehalose metabolism is also important for normal plant growth and development. The intermediate compound - trehalose-6-phosphate (T6P) - is now confirmed to act as a sensor for available sucrose, hereby directly influencing the type of response to the changing environmental conditions. This is possible because T6P and/or trehalose or their biosynthetic enzymes are part of complex interaction networks with other crucial hormone and sugar-induced signaling pathways, which may function at different developmental stages. Because of its effect on plant growth and development, modification of trehalose biosynthesis, either at the level of T6P synthesis, T6P hydrolysis, or trehalose hydrolysis, has been utilized to try to improve crop yield and biomass. It was shown that alteration of the amounts of either T6P and/or trehalose did result in increased stress tolerance, but also resulted in many unexpected phenotypic alterations. A main challenge is to characterize the part of the signaling pathway resulting in improved stress tolerance, without affecting the pathways resulting in the unwanted phenotypes. One such specific pathway where modification of trehalose metabolism improved stress tolerance, without any side effects, was recently obtained by overexpression of trehalase, which results in a more sensitive reaction of the stomatal guard cells and closing of the stomata under drought stress conditions. We have used the data that have been obtained from different studies to generate the optimal plant that can be constructed based on modifications of trehalose metabolism.

Biochemical characterization and ligand-binding properties of trehalose-6-phosphate phosphatase from Mycobacterium tuberculosis

Trehalose-6-phosphate phosphatase (TPP) is an essential enzyme for growth of mycobacteria, which has been identified to be a potential anti-tuberculosis drug target. However, the biochemical and ligand-binding properties and the 3D structure of TPP remain unclear so far. In the present study, we expressed the recombinant TPP protein from Mycobacterium tuberculosis (otsB2/Rv3372). Results from the far-ultraviolet circular dichroism experiments indicated that the secondary structure of TPP was rich in α-helix with a lower structural stability (Cm = 2.099 ± 0.134 M). Ligand-binding assay by isothermal titration calorimetry demonstrated that the recombinant TPP protein could bind with trehalose-6-P in the presence of Mg(2+) (Kd = 39.52 ± 1.78 μM) with a molar ratio of 1 : 1. In addition, the 3D structure of TPP was modeled by I-TASSER, indicating that the TPP protein was composed of a hydrolase domain, a cap domain, and an N-terminal domain. Flexible docking was further conducted by using the Simulations/Dock module of the Molecular Operating Environment software. The binding pocket of TPP for both trehalose-6-P and Mg(2+) was determined, which was located on the interface between the hydrolase domain and the cap domain. Asp149, Gly186, Arg187, Arg291, and Glu295 were identified to be the key residues for TPP binding with trehalose-6-P. This work may lay the basis for further structural and functional studies of TPP and TPP-related novel drug development.

Exploiting genes and functional diversity of chlorogenic acid and luteolin biosyntheses in Lonicera japonica and their substitutes

Chlorogenic acids (CGAs) and luteolin are active compounds in Lonicera japonica, a plant of high medicinal value in traditional Chinese medicine. This study provides a comprehensive overview of gene families involved in chlorogenic acid and luteolin biosynthesis in L. japonica, as well as its substitutes Lonicera hypoglauca and Lonicera macranthoides. The gene sequence feature and gene expression patterns in various tissues and buds of the species were characterized. Bioinformatics analysis revealed that 14 chlorogenic acid and luteolin biosynthesis-related genes were identified from the L. japonica transcriptome assembly. Phylogenetic analyses suggested that the function of individual gene could be differentiation and induce active compound diversity. Their orthologous genes were also recognized in L. hypoglauca and L. macranthoides genomic datasets, except for LHCHS1 and LMC4H2. The expression patterns of these genes are different in the tissues of L. japonica, L. hypoglauca and L. macranthoides. Results also showed that CGAs were controlled in the first step of biosynthesis, whereas both steps controlled luteolin in the bud of L. japonica. The expression of LJFNS2 exhibited positive correlation with luteolin levels in L. japonica. This study provides significant information for understanding the functional diversity of gene families involved in chlorogenic acid and the luteolin biosynthesis, active compound diversity of L. japonica and its substitutes, and the different usages of the three species.