RhVI1 is a membrane-anchored vacuolar invertase highly expressed in Rosa hybrida L. petals

Genome-wide identification and characterization of the sucrose invertase gene family in Hemerocallis citrina

Background

Sucrose invertase is an important catalytic enzyme that is widely distributed in plants and can irreversibly hydrolyze sucrose into fructose and glucose. Daylily is an important perennial flower worldwide and a traditional vegetable in East Asia. Previous studies have suggested that sucrose invertase is involved in the aging of daylily flowers. However, knowledge about the number, physicochemical properties, and expression patterns of daylily sucrose invertases is still lacking. Identifying the daylily sucrose invertase family genes in the genome is highly important for understanding phylogenetic evolution and determining the genetic function of sucrose invertase.

Methods

To obtain basic knowledge about the number, classification, sequence composition, and physicochemical properties of sucrose invertases in daylily, bioinformatics software was used to analyze the genome of Hemerocallis citrina (H. citrina), and the basic properties of sucrose invertase genes and proteins were obtained. Then, combined with transcriptome data from flower organs at different developmental stages, the expression patterns of each gene were clarified. Finally, the reliability of the transcriptome data was verified by quantitative real-time polymerase chain reaction (PCR).

Results

Through software analysis, 35 sucrose invertases were identified from the H. citrina genome and named HcINV1-HcINV35; these enzymes belong to three subfamilies: cell wall invertases, vacuolar invertases, and chloroplast invertases. The amino acid composition, motif types, promoter composition, gene structure, protein physicochemical properties, gene chromosomal localization, and evolutionary adaptability of daylily invertases were determined; these results provided a comprehensive understanding of daylily invertases. The transcriptome expression profile combined with fluorescence quantitative reverse transcription-polymerase chain reaction (RT‒PCR) analysis suggested that almost all daylily invertase genes were expressed in flower organs, but even genes belonging to the same subfamily did not exhibit the same expression pattern at different developmental stages, suggesting that there may be redundancy or dissimilation in the function of daylily sucrose invertases.

Abscisic Acid Regulates Carbohydrate Metabolism, Redox Homeostasis and Hormonal Regulation to Enhance Cold Tolerance in Spring Barley

Abscisic acid (ABA) plays a vital role in the induction of low temperature tolerance in plants. To understand the molecular basis of this phenomenon, we performed a proteomic analysis on an ABA-deficit mutant barley (Az34) and its wild type (cv Steptoe) under control conditions (25/18 °C) and after exposure to 0 °C for 24 h. Most of the differentially abundant proteins were involved in the processes of photosynthesis and metabolisms of starch, sucrose, carbon, and glutathione. The chloroplasts in Az34 leaves were more severely damaged, and the decrease in Fv/Fm was larger in Az34 plants compared with WT under low temperature. Under low temperature, Az34 plants possessed significantly higher activities of ADP-glucose pyrophosphorylase, fructokinase, monodehydroascorbate reductase, and three invertases, but lower UDP-glucose pyrophosphorylase activity than WT. In addition, concentrations of proline and soluble protein were lower, while concentration of H₂O₂ was higher in Az34 plants compared to WT under low temperature. Collectively, the results indicated that ABA deficiency induced modifications in starch and sucrose biosynthesis and sucrolytic pathway and overaccumulation of reactive oxygen species were the main reason for depressed low temperature tolerance in barley, which provide novel insights to the response of barley to low temperature under future climate change.

Cloning and functional analysis of soluble acid invertase 2 gene (SbSAI-2) in sorghum

The sorghum soluble acid invertase gene SbSAI-2 was cloned and the function verified in Pichia pastoris and rice, showing the SbSAI-2 affects composition and content of sugar in stem juice. Sugar metabolism is one of the most important metabolic processes in plants, in which soluble acid invertase plays a key role. However, the structure and function of the soluble acid transferase gene in sorghum are still fully unclear. In this study, SbSAI-2 was cloned from the sorghum variety BTx623, and two transcripts were found through sequence analysis, with only one transcript translated into an active protein. There is 72% homology between SbSAI-2 and OsVIN2. The construction of Osvin2 mutant lines and SbSAI-2-1 overexpression lines in Oryza sativa L. japonica. cv. Nipponbare were produced to clarify the invertase functionality. While the invertase activity in the stem of the Osvin2 mutant line was reduced, with no significant difference (P  > 0.05), and the contents of fructose and glucose in stem tissue did not change significantly (P  > 0.05), and the content of sucrose increased by 38.89% (P  < 0.01). In SbSAI-2-1 overexpression lines, the invertase activity in stem was increased by more than 20 times (P  < 0.01). The contents of glucose and fructose in stem tissues were increased by two and three times, respectively (P  < 0.01), while the content of sucrose was significantly decreased, which was below the detection limit (P  < 0.01). This study indicated that SbSAI-2 is a key enzyme related to sucrose metabolism and affects the composition and content of sugar in stems. The result provided further the gene function verification and laid a foundation for the development of molecular markers.

Shedding light on the presymbiontic phase of C. arietinum

A complex network of symbiotic events between plants and bacteria allows the biosphere to exploit the atmospheric reservoir of molecular nitrogen. In seeds, a series of presymbiotic steps are already identified during imbibition, while interactions between the host and its symbiont begin in the early stages of germination. In the present study, a detailed analysis of the substances' complex delivered by Cicer arietinum seeds during imbibition showed a relevant presence of proteins and amino acids, which, except for cysteine, occurred with the whole proteinogenic pool. The imbibing solution was found to provide essential probiotic properties able to sustain the growth of the specific chickpea symbiont Mesorhizobium ciceri. Moreover, the imbibing solution, behaving as a complete medium, was found to be critically important for the symbiont's attraction, a fact this that is strictly related to the presence of the amino acids glycine, serine, and threonine. Here, the presence of these amino acids is constantly supported by the presence of the enzymes serine hydroxymethyltransferase and formyltetrahydrofolate deformylase, which are both involved in their biosynthesis. The reported findings are discussed in the light of the pivotal role played by the imbibing solution in attracting and sustaining symbiosis between the host and its symbiont.

Characterization under quasi-native conditions of the capsanthin/capsorubin synthase from Capsicum annuum L

Chromoplasts are typical plastids of fruits and flowers, deriving from chloroplasts through complex processes of re-organization and recycling. Since this transition leads to the production of reactive species, chromoplasts are characteristic sites for biosynthesis and accumulation of carotenoids and other antioxidants. Here, we have analysed the chromoplast membranes from Capsicum annuum L. fruits, finding a significant expression of the capsanthin/capsorubin synthase. This enzyme was isolated by a very mild procedure allowing its analyses under quasi-native conditions. The isolated complex appeared as a red coloured homo-trimer, suggesting the retention of at least one of the typical carotenoids from C. annuum. Moreover, the protein complex was co-purified with a non-proteinaceous fraction of carotenoid aggregates carrying a high molecular weight and separable only by Size Exclusion Chromatography. This last finding suggested a relationship between the carotenoids synthesis on chromoplast membranes, the presence, and storage of organised carotenoids aggregates typical for chromoplasts. Further MS analyses also provided important hints on the interactome network associated to the capsanthin/capsorubin synthase, confirming its functional relevance during ripening. Results are discussed in the frame of the primary role played by carotenoids in quenching the growing oxidative stress during fruits ripening.

The Role of Iron and Copper on the Oligomerization Dynamics of DR_2577, the Main S-Layer Protein of Deinococcus radiodurans

Surface (S)-layers are cryptic structures that coat the external surface of the bacterial cell in many species. The paracrystalline regularity of the S-layer is due to the self-assembling of one or more protein units. The property of self-assembling seems to be mediated by specific topologies of the S-layer proteins as well as the presence of specific ions that provide support in building and stabilizing the bi-dimensional S-layer organization. In the present study, we have investigated the self-assembling mechanism of the main S-layer protein of Deinococcus radiodurans (DR_2577) finding an unusual role played by Fe³⁺ and Cu²⁺ in the oligomerization of this protein. These findings may trace a structural and functional metallo-mediated convergence between the role of these metals in the assembling of the S-layer and their well-known roles in protecting against oxidative stress in D. radiodurans.

iTRAQ-based quantitative proteomic analysis reveals dynamic changes during daylily flower senescence

Sugar-related metabolic biological processes and metabolic pathways as well as invertase, protease, and ribosomal proteins may be critical regulators controlling the circadian rhythm and ephemeral properties of daylily flowers. Daylily is a familiar perennial flower. The daylily flower opens at dawn and withers away at night. Flower longevity in almost all daylily varieties from opening to fading is less than 24 h. In the past decades, the physiological changes and genetic responses to senescence in daylily flowers have been reported. However, the main metabolic pathways and biological processes involved in daylily flower senescence and the proteins involved in premature senility of daylily flowers are poorly understood. Herein, we identified differences between the proteomes of four developmental stages (s1-s4) of daylily flowers using iTRAQ-based quantitative proteomic methods. A total of 445 proteins (containing at least two unique peptides) were identified, and differentially expressed proteins (upregulation ≥ 1.5 or downregulation ≤ 0.67, P value ≤ 0.05) were detected between these stages in the following numbers: 58 (s2/s1), 59 (s3/s1), 31 (s3/s2), 64 (s4/s1), 52 (s4/s2), and 29 (s4/s3). Protein functions and classifications were analyzed based on GO, KEGG, and COG, and expressive hierarchical cluster analysis and functional enrichment analysis for differentially expressed proteins were carried out. A comparison of the late stages (s3 and s4) with the early stage (s1) revealed that the sugar (hexose, monosaccharide, and glucose) metabolic process GO category was the most enriched, and sugar (galactose, pentose, starch, and sucrose) metabolism pathways constituted the most enriched KEGG category. Finally, the potential research value of invertase, protease, and ribosomal proteins for revealing the mechanism underlying the circadian rhythm and ephemeral properties of daylily flowers are discussed. These data and analyses provide new insight into the senescence mechanism of daylily flowers.

On the S-layer of Thermus thermophilus and the assembling of its main protein SlpA

We have isolated and analysed the cell envelope of the thermophilic bacterium Thermus thermophilus HB8. Isolated cell walls, characterized by the dominance of the S-layer protein SlpA, are found to be constituted by several protein complexes of high molecular weights. Further isolation steps, starting from the cell wall samples, led to the selective release of the S-layer protein SlpA in solution as confirmed by mass spectrometry. Blue Native gel electrophoresis on these samples showed that SlpA is organized into a specific hierarchical order of oligomeric states that are consistent with the complexes at high molecular weight identified on the total cell wall fraction. The analysis showed that SlpA bases this peculiar organization on monomers and exceptionally stable dimers, leading to the formation of tetramers, heptamers, and decamers. Furthermore, the two elementary units of SlpA, monomers and dimers, are regulated by the presence of calcium not only for the assembling of monomers into dimers, but also for the splitting of dimers into monomers. Finally, the SlpA protein was found to be subjected to specific proteolysis leading to characteristic degradation products. Findings are discussed in terms of S-layer assembling properties as bases for understanding its structure, turn-over and organization.

Roles played by invertase and gene expression in the development of the horn-shaped gall on leaves of Rhus chinensis

The present study deals with the growth and development of the horn-shaped gall, which is induced by Schlechtendalia chinensis Bell. on leaves of Rhus chinensis Mill. The relationship between gall formers and their host plants was investigated by means of the activities of various invertases, the expressions of the cell wall invertase gene (INV2), and vacuolar invertase gene (INV3) during gall development. Our results show that the increase in the sink strength of the galls required cell wall invertase and vacuolar invertase, and that vacuolar invertase had a particular impact during the early development. In addition, vacuolar invertase activity was always significantly higher in galls than in leaves. However, ionically bound cell wall invertase showed a slightly significant increased activity level when compared with the leaves after galls had entered the fast growing period. This result indicates that vacuolar invertase is related to the rapid expansion of the galls, but ionically bound cell wall invertase is involved in the rapid growth of tissues. The enhanced activity of cell wall invertase and the expression of INV2 may be a plant response to a gall-induced stress. Cytoplasmic invertase that acts as a maintenance enzyme, or takes part in the production of secondary metabolites, was elevated when intracellular acid invertase activity decreased.

New insights into the operative network of FaEO, an enone oxidoreductase from Fragaria x ananassa Duch

The 2-methylene-furan-3-one reductase or Fragaria x ananassa Enone Oxidoreductase (FaEO) catalyses the last reductive step in the biosynthesis of 4-hydroxy-2,5-dimethyl-3(2H)-furanone, a major component in the characteristic flavour of strawberries. In the present work, we describe the association between FaEO and the vacuolar membrane of strawberry fruits. Even if FaEO lacks epitopes for stable or transient membrane-interactions, it contains a calmodulin-binding region, suggesting that in vivo FaEO may be associated with the membrane via a peripheral protein complex with calmodulin. Moreover, we also found that FaEO occurs in dimeric form in vivo and, as frequently observed for calmodulin-regulated proteins, it may be expressed in different isoforms by alternative gene splicing. Further mass spectrometry analysis confirmed that the isolated FaEO consists in the already known isoform and that it is the most characteristic during ripening. Finally, a characterization by absorption spectroscopy showed that FaEO has specific flavoprotein features. The relevance of these findings and their possible physiological implications are discussed.