AtTCTP2, an Arabidopsis thaliana homolog of Translationally Controlled Tumor Protein, enhances in vitro plant regeneration

Cucumber (Cucumis sativus L.) translationally controlled tumor protein interacts with CsRab11A and promotes activation of target of rapamycin in response to Podosphaera xanthii

The target of rapamycin (TOR) kinase serves as a central regulator that integrates nutrient and energy signals to orchestrate cellular and organismal physiology in both animals and plants. Despite significant advancements having been made in understanding the molecular and cellular functions of plant TOR kinases, the upstream regulators that modulate TOR activity are not yet fully elucidated. In animals, the translationally controlled tumor protein (TCTP) is recognized as a key player in TOR signaling. This study reveals that two TCTP isoforms from Cucumis sativus, when introduced into Arabidopsis, are instrumental in balancing growth and defense mechanisms against the fungal pathogen Golovinomyces cichoracearum. We hypothesize that plant TCTPs act as upstream regulators of TOR in response to powdery mildew caused by Podosphaera xanthii in Cucumis. Our research further uncovers a stable interaction between CsTCTP and a small GTPase, CsRab11A. Transient transformation assays indicate that CsRab11A is involved in the defense against P. xanthii and promotes the activation of TOR signaling through CsTCTP. Moreover, our findings demonstrate that the critical role of TOR in plant disease resistance is contingent upon its regulated activity; pretreatment with a TOR inhibitor (AZD-8055) enhances cucumber plant resistance to P. xanthii, while pretreatment with a TOR activator (MHY-1485) increases susceptibility. These results suggest a sophisticated adaptive response mechanism in which upstream regulators, CsTCTP and CsRab11A, coordinate to modulate TOR function in response to P. xanthii, highlighting a novel aspect of plant-pathogen interactions.

Bacillus Strains as Effective Biocontrol Agents Against Phytopathogenic Bacteria and Promoters of Plant Growth

Modern crop production relies on the application of chemical pesticides and fertilizers causing environmental and economic challenges. In response, less environmentally impactful alternatives have emerged such as the use of beneficial microorganisms. These microorganisms, particularly plant growth-promoting bacteria (PGPB), have demonstrated their ability to enhance plant growth, protect against various stresses, and reduce the need for chemical inputs. Among the PGPB, Bacillus species have garnered attention due to their adaptability and commercial potential. Recent reports have highlighted Bacillus strains as biocontrol agents against phytopathogenic bacteria while concurrently promoting plant growth. We also examined Bacillus plant growth-promoting abilities in Arabidopsis thaliana seedlings. In this study, we assessed the potential of various Bacillus strains to control diverse phytopathogenic bacteria and inhibit quorum sensing using Chromobacterium violaceum as a model system. In conclusion, our results suggest that bacteria of the genus Bacillus hold significant potential for biotechnological applications. This includes developments aimed at reducing agrochemical use, promoting sustainable agriculture, and enhancing crop yield and protection.

Comprehensive analysis of Translationally Controlled Tumor Protein (TCTP) provides insights for lineage-specific evolution and functional divergence

BACKGROUND

Translationally controlled tumor protein (TCTP) is a conserved, multifunctional protein involved in numerous cellular processes in eukaryotes. Although the functions of TCTP have been investigated sporadically in animals, invertebrates, and plants, few lineage-specific activities of this molecule, have been reported. An exception is in Arabidopsis thaliana, in which TCTP (AtTCTP1) functions in stomatal closuer by regulating microtubule stability. Further, although the development of next-generation sequencing technologies has facilitated the analysis of many eukaryotic genomes in public databases, inter-kingdom comparative analyses using available genome information are comparatively scarce.

METHODOLOGY

To carry out inter-kingdom comparative analysis of TCTP, TCTP genes were identified from 377 species. Then phylogenetic analysis, prediction of protein structure, molecular docking simulation and molecular dynamics analysis were performed to investigate the evolution of TCTP genes and their binding proteins.

RESULTS

A total of 533 TCTP genes were identified from 377 eukaryotic species, including protozoa, fungi, invertebrates, vertebrates, and plants. Phylogenetic and secondary structure analyses reveal lineage-specific evolution of TCTP, and inter-kingdom comparisons highlight the lineage-specific emergence of, or changes in, secondary structure elements in TCTP proteins from different kingdoms. Furthermore, secondary structure comparisons between TCTP proteins within each kingdom, combined with measurements of the degree of sequence conservation, suggest that TCTP genes have evolved to conserve protein secondary structures in a lineage-specific manner. Additional tertiary structure analysis of TCTP-binding proteins and their interacting partners and docking simulations between these proteins further imply that TCTP gene variation may influence the tertiary structures of TCTP-binding proteins in a lineage-specific manner.

CONCLUSIONS

Our analysis suggests that TCTP has undergone lineage-specific evolution and that structural changes in TCTP proteins may correlate with the tertiary structure of TCTP-binding proteins and their binding partners in a lineage-specific manner.

Integration of QTL Mapping and Gene Fishing Techniques to Dissect the Multi-Main Stem Trait in Rapeseed (Brassica napus L.)

Rapeseed is one of the most important oilseed crops in the world. Improving the production of rapeseed is beneficial to relieve the shortage of edible vegetable oil. As the organ of support and transport, the main stem of rapeseed controls the plant architecture, transports the water and nutrients, and determines the number of inflorescence. Increasing the number of main stems would be helpful for the yield improvement in Brassica napus (B. napus). This attractive multi-main stem (MMS) trait was observed in the KN DH population. We investigated not only the frequency of MMS traits but also dissected the genetic basis with QTL mapping analysis and Gene-Fishing technique. A total of 43 QTLs were identified for MMS based on high-density linkage map, which explained 2.95-14.9% of the phenotypic variation, among which two environmental stable QTLs (cqMMS.A3-2 and cqMMS.C3-5) were identified in winter and semi-winter environments. Epistatic interaction analysis indicated cqMMS.C3-5 was an important loci for MMS. According to the functional annotation, 159 candidate genes within QTL confidence intervals, corresponding to 148 Arabidopsis thaliana (A. thaliana) homologous genes, were identified, which regulated lateral bud development and tiller of stem, such as shoot meristemless (STM), WUSCHEL-regulated-related genes, cytokinin response factors (CRF5), cytokinin oxidase (CKX4), gibberellin-regulated (RDK1), auxin-regulated gene (ARL, IAR4), and auxin-mediated signaling gene (STV1). Based on Gene-Fishing analysis between the natural plants and the double-main stem (DMS) plant, 31 differentially expressed genes (DEGs) were also obtained, which were related to differentiation and formation of lateral buds, biotic stimulus, defense response, drought and salt-stress responses, as well as cold-response functional genes. In addition, by combining the candidate genes in QTL regions with the DEGs that were obtained by Gene-Fishing technique, six common candidate genes (RPT2A, HLR, CRK, LRR-RLK, AGL79, and TCTP) were identified, which might probably be related to the formation of MMS phenotype. The present results not only would give a new insight into the genetic basis underlying the regulation of MMS but also would provide clues for plant architecture breeding in rapeseed.

m5C Methylation Guides Systemic Transport of Messenger RNA over Graft Junctions in Plants

In plants, transcripts move to distant body parts to potentially act as systemic signals regulating development and growth. Thousands of messenger RNAs (mRNAs) are transported across graft junctions via the phloem to distinct plant parts. Little is known regarding features, structural motifs, and potential base modifications of transported transcripts and how these may affect their mobility. We identified Arabidopsis thaliana mRNAs harboring the modified base 5-methylcytosine (m⁵C) and found that these are significantly enriched in mRNAs previously described as mobile, moving over graft junctions to distinct plant parts. We confirm this finding with graft-mobile methylated mRNAs TRANSLATIONALLY CONTROLLED TUMOR PROTEIN 1 (TCTP1) and HEAT SHOCK COGNATE PROTEIN 70.1 (HSC70.1), whose mRNA transport is diminished in mutants deficient in m⁵C mRNA methylation. Together, our results point toward an essential role of cytosine methylation in systemic mRNA mobility in plants and that TCTP1 mRNA mobility is required for its signaling function.

The Two Translationally Controlled Tumor Protein Genes, CsTCTP1 and CsTCTP2, Are Negative Modulators in the Cucumis sativus Defense Response to Sphaerotheca fuliginea

Pathogen stress often significantly decreases cucumber production. However, knowledge regarding the molecular mechanism and signals of cucumber disease resistance is far from complete. Here, we report two translationally controlled tumor protein genes, CsTCTP1 and CsTCTP2, that are both negative modulators in the Cucumis sativus defense response to Sphaerotheca fuliginea. Subcellular localization analysis showed that CsTCTP1 and CsTCTP2 were both localized in the cytoplasm. Expression analysis indicated that the transcript levels of CsTCTP1 and CsTCTP2 were linked to the degree of cucumber resistance to S. fuliginea. Transient overexpression of either CsTCTP1 or CsTCTP2 in cucumber cotyledons impaired resistance to S. fuliginea, whereas silencing of either CsTCTP1 or CsTCTP2 enhanced cucumber resistance to S. fuliginea. The relationship of several defense-related genes and ABA and target of rapamycin (TOR) signaling pathway-related genes to the overexpressing and silencing of CsTCTP1/CsTCTP2 in non-infested cucumber plants was investigated. The results indicated that CsTCTP1 participates in the defense response to S. fuliginea by regulating the expression of certain defense-associated genes and/or ABA signaling pathway-associated genes, and CsTCTP2 participates through regulating the expression of TOR signaling pathway-associated genes. Our findings will guide enhancing the resistance of cucumber to powdery mildew.

The Plastid and Mitochondrial Peptidase Network in Arabidopsis thaliana: A Foundation for Testing Genetic Interactions and Functions in Organellar Proteostasis

Plant plastids and mitochondria have dynamic proteomes. Protein homeostasis in these organelles is maintained by a proteostasis network containing protein chaperones, peptidases, and their substrate recognition factors. However, many peptidases, as well as their functional connections and substrates, are poorly characterized. This review provides a systematic insight into the organellar peptidase network in Arabidopsis thaliana We present a compendium of known and putative Arabidopsis peptidases and inhibitors, and compare the distribution of plastid and mitochondrial peptidases to the total peptidase complement. This comparison shows striking biases, such as the (near) absence of cysteine and aspartic peptidases and peptidase inhibitors, whereas other peptidase families were exclusively organellar; reasons for such biases are discussed. A genome-wide mRNA-based coexpression data set was generated based on quality controlled and normalized public data, and used to infer additional plastid peptidases and to generate a coexpression network for 97 organellar peptidase baits (1742 genes, making 2544 edges). The graphical network includes 10 modules with specialized/enriched functions, such as mitochondrial protein maturation, thermotolerance, senescence, or enriched subcellular locations such as the thylakoid lumen or chloroplast envelope. The peptidase compendium, including the autophagy and proteosomal systems, and the annotation based on the MEROPS nomenclature of peptidase clans and families, is incorporated into the Plant Proteome Database.

Molecular characterization, expression analysis and heterologous expression of two translationally controlled tumor protein genes from Cucumis sativus

The translationally controlled tumor protein (TCTP) is a family of abundant and ubiquitous proteins involved in several important primary functions. Cucumbers harbor two TCTP genes, CsTCTP1 and CsTCTP2; however, their functional roles remain unclear. In this study, we isolated CsTCTP1 and CsTCTP2 (XP-004134215 and XP-004135602, respectively) promoters, full-length cDNA and genomic sequences from Cucumis sativus. Bioinformatics analysis, containing cis-acting elements, structural domains, phylogenetic tree and conserved motifs, suggested the conservation and divergence of CsTCTP1 and CsTCTP2, thus providing knowledge regarding their functions. Expression analysis indicated that CsTCTP1 and CsTCTP2 exhibited tissue-specific expression and were regulated by biotic or abiotic stresses in C. sativus. Furthermore, CsTCTP1 and CsTCTP2 were regulated by ABA and may be associated with the TOR (target of rapamycin) signaling pathway. In a prokaryotic expression analysis, CsTCTP1 and CsTCTP2 showed positive responses to salt and heat stresses and a negative response to drought and HgCl2 stresses. TCTP may exert multiple functions in various cellular processes.

Proteomic analysis of Potentilla fruticosa L. leaves by iTRAQ reveals responses to heat stress

High temperature is an important environmental factor that affects plant growth and crop yield. Potentilla fruticosa L. has a developed root system and characteristics of resistance to several stresses (e.g., high temperature, cold, drought) that are shared by native shrubs in the north and west of China. To investigate thermotolerance mechanisms in P. fruticosa, 3-year-old plants were subjected to a high temperature of 42°C for 1, 2, and 3 days respectively before analysis. Then, we studied changes in cell ultrastructure using electron microscopy and investigated physiological changes in the leaves of P. fruticosa. Additionally, we used isobaric tags for relative and absolute quantification (iTRAQ) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to study proteomic changes in P. fruticosa leaves after 3 d of 42°C heat stress. we found that the cell membrane and structure of chloroplasts, especially the thylakoids in P. fruticosa leaves, was destroyed by a high temperature stress, which might affect the photosynthesis in this species. We identified 35 up-regulated and 23 down-regulated proteins after the heat treatment. Gene Ontology (GO) analysis indicated that these 58 differentially abundant proteins were involved mainly in protein synthesis, protein folding and degradation, abiotic stress defense, photosynthesis, RNA process, signal transduction, and other functions. The 58 proteins fell into different categories based on their subcellular localization mainly in the chloroplast envelope, cytoplasm, nucleus, cytosol, chloroplast, mitochondrion and cell membrane. Five proteins were selected for analysis at the mRNA level; this analysis showed that gene transcription levels were not completely consistent with protein abundance. These results provide valuable information for Potentilla thermotolerance breeding.

Impacts of the overexpression of a tomato translationally controlled tumor protein (TCTP) in tobacco revealed by phenotypic and transcriptomic analysis

KEY MESSAGE

Overexpression of a tomato TCTP impacts plant biomass production and performance under stress. These phenotypic alterations were associated with the up-regulation of genes mainly related to photosynthesis, fatty acid metabolism and water transport. The translationally controlled tumor protein (TCTP) is a multifaceted and highly conserved eukaryotic protein. In plants, despite the existence of functional data implicating this protein in cell proliferation and growth, the detailed physiological roles of many plant TCTPs remain poorly understood. Here we focused on a yet uncharacterized TCTP from tomato (SlTCTP). We show that, when overexpressed in tobacco, SlTCTP may promote plant biomass production and affect performance under salt and osmotic stress. Transcriptomic analysis of the transgenic plants revealed the up-regulation of genes mainly related to photosynthesis, fatty acid metabolism and water transport. This induced photosynthetic gene expression was paralleled by an increase in the photosynthetic rate and stomatal conductance of the transgenic plants. Moreover, the transcriptional modulation of genes involved in ABA-mediated regulation of stomatal movement was detected. On the other hand, genes playing a pivotal role in ethylene biosynthesis were found to be down-regulated in the transgenic lines, thus suggesting deregulated ethylene accumulation in these plants. Overall, these results point to a role of TCTP in photosynthesis and hormone signaling.

Structure-Function Relationship of TCTP

The translationally controlled tumor protein (TCTP) is a small, multifunctional protein found in most, if not all, eukaryotic lineages, involved in a myriad of key regulatory processes. Among these, the control of proliferation and inhibition of cell death, as well as differentiation, are the most important, and it is probable that other responses are derived from the ability of TCTP to influence them in both unicellular and multicellular organisms. In the latter, an additional function for TCTP stems from its capacity to be secreted via a nonclassical pathway and function in a non-cell autonomous (paracrine) manner, thus affecting the responses of neighboring or distant cells to developmental or environmental stimuli (as in the case of serum TCTP/histamine-releasing factor in mammals and phloem TCTP in Arabidopsis). The additional ability to traverse membranes without a requirement for transmembrane receptors adds to its functional flexibility. The long-distance transport of TCTP mRNA and protein in plants via the vascular system supports the notion that an important aspect of TCTP function is its ability to influence the response of neighboring and distant cells to endogenous and exogenous signals in a supracellular manner. The predicted tridimensional structure of TCTPs indicates a high degree of conservation, more than its amino acid sequence similarity could suggest. However, subtle differences in structure could lead to different activities, as evidenced by TCTPs secreted by Plasmodium spp. Similar structural variations in animal and plant TCTPs, likely the result of convergent evolution, could lead to deviations from the canonical function of this group of proteins, which could have an impact from a biomedical and agricultural perspectives.

Role of TCTP for Cellular Differentiation and Cancer Therapy

The translationally controlled tumor protein (TCTP) is a highly conserved protein that is regulated due to a high number of extracellular stimuli. TCTP has an important role for cell cycle and normal development. On the other side, tumor reversion and malignant transformation have been associated with TCTP. TCTP has been found among the 12 genes that are differentially expressed during mouse oocyte maturation, and an overexpression of this gene was reported in a wide variety of different cancer types. Its antiapoptotic effect is indicated by the interaction with several proapoptotic proteins of the Bcl-2 family and the p53 tumor suppressor protein. In this article, we draw attention to the role of TCTP in cancer, especially, focusing on cell differentiation and tumor reversion, a biological process by which highly tumorigenic cells lose their malignant phenotype. This protein has been shown to be the most strongly downregulated protein in revertant cells compared to the parental cancer cells. Decreased expression of TCTP results either in the reprogramming of cancer cells into reversion or apoptosis. As conventional chemotherapy is frequently associated with the development of drug resistance and high toxicity, the urge for the development of new or additional scientific approaches falls into place. Differentiation therapy aims at reinducing differentiation backward to the nonmalignant cellular state. Here, different approaches have been reported such as the induction of retinoid pathways and the use of histone deacetylase inhibitors. Also, PPARγ agonists and the activation of the vitamin D receptor have been reported as potential targets in differentiation therapy. As TCTP is known as the histamine-releasing factor, antihistaminic drugs have been shown to target this protein. Antihistaminic compounds, hydroxyzine and promethazine, inhibited cell growth of cancer cells and decreased TCTP expression of breast cancer and leukemia cells. Recently, we found that two antihistaminics, levomepromazine and buclizine, inhibited cancer cell growth by direct binding to TCTP and induction of cell differentiation. These data confirmed that TCTP is an exquisite target for anticancer differentiation therapy and antihistaminics have potential to be lead compounds for the direct interaction with TCTP as new inhibitors of human TCTP and tumor growth.

AtTCTP2 mRNA and protein movement correlates with formation of adventitious roots in tobacco

The Translationally Controlled Tumor Proteins, or TCTP, is a superfamily of exclusively eukaryotic proteins essential in the regulation of proliferation and general growth. However, it is clear that these are multifunctional proteins given (1) the pleiotropic effects of its mutations, and (2), the multiple processes in which this protein is involved. TCTP function in general is conserved, since Arabidopsis AtTCTP1 can rescue a Drosophila mutant, and vice versa. It has become clear, however, that these proteins may have "taxon-specific" functions. In the case of plants, mRNA and/or proteins have been found in the phloem translocation stream of different species, suggesting a role in long-distance signaling. We have found that a second Arabidopsis TCTP gene, AtTCTP2, codes for a protein that moves long-distance through a graft union in tobacco. Interestingly, the mRNA is also transported long-distance. Both mRNA and protein move long-distance; interestingly, the movement, while more efficient from source to sink tissues, also occurs in the opposite direction. The protein reaches the nuclei of parenchyma cells and adventitious roots. Furthermore, it is clear that the long-distance delivery of AtTCTP2 protein and mRNA is required for the induction of adventitious roots. A model is presented that accounts for these observations.