Effects of Pieris japonica (Ericaceae) dominance on cool temperate forest altered-understory environments and soil microbiomes in Southern Japan

The number of plants unpalatable to deer increases with increasing deer numbers. In the Kyushu Mountain area of Southern Japan, Pieris japonica (Ericaceae), an unpalatable shrub, has become the monodominant vegetation under evergreen conifer and deciduous broad-leaved tree stands. The monodominance of unpalatable plants in the understory has potential advantages and drawbacks; however, the effects of Pieris dominance are not well understood. To assess the effects of P. japonica dominances on forest environments and ecosystems, we investigated understory environments and soil microbiomes in Pieris-dominant sites. Under the deciduous broad-leaved trees, Pieris dominance leads to considerable Pieris leaf litter and humus weights and low soil bulk density and canopy openness. In the soil fungal community and fungal functional groups, the relative abundance of symbiotrophic fungi, particularly ectomycorrhizal fungi in Pieris-dominant sites were lower than in other-vegetation understory sites and saprotrophic fungi vice versa. Because few seedlings and saplings were found under Pieris shrubs, Pieris dominance in the understory might exclude other plant species. The results of this study will contribute to the Pieris population and forest management following deer overgrazing.

Upregulation of MAP kinase HOG1 gene of white-rot fungus Phlebia sp. MG-60 inhibits the ethanol fermentation and mycelial growth

Wood biomass conversion for fossil resource replacement could result in the sustainable production of chemicals, although lignin represents an obstacle to efficient polysaccharide use. White-rot fungus Phlebia sp. MG-60 reportedly selectively and aerobically degrades lignin in hardwood, then it begins cellulose saccharification from the delignified wood to produce ethanol. Environmental conditions might change white-rot fungi-driven biomass conversion. However, how the environmental response sensor affects ethanol fermentation in white-rot fungi remains elusive. In this study, we focused on MGHOG1, the yeast Hog1 homolog in Phlebia sp. MG-60, a presumably important player in osmoresponse. We generated MGHOG1 overexpressing (OE) transformants in Phlebia sp. MG-60, exhibiting slower mycelial growth compared with the wild-type under salinity stress. MGHOG1 overexpressing liquid cultures displayed suppressed mycelial growth and ethanol fermentation. Therefore, MGHOG1 potentially influences ethanol fermentation and mycelial growth in Phlebia sp. MG-60. This study provides novel insights into the regulation of white-rot fungi-mediated biomass conversion.

Correction to: Assessment of Polygala paniculata (Polygalaceae) characteristics for evolutionary studies of legume-rhizobia symbiosis

A correction to this paper has been published: https://doi.org/10.1007/s10265-021-01295-3

Structure-function studies of ultrahigh molecular weight isoprenes provide key insights into their biosynthesis

Some plant trans-1,4-prenyltransferases (TPTs) produce ultrahigh molecular weight trans-1,4-polyisoprene (TPI) with a molecular weight of over 1.0 million. Although plant-derived TPI has been utilized in various industries, its biosynthesis and physiological function(s) are unclear. Here, we identified three novel Eucommia ulmoides TPT isoforms—EuTPT1, 3, and 5, which synthesized TPI in vitro without other components. Crystal structure analysis of EuTPT3 revealed a dimeric architecture with a central hydrophobic tunnel. Mutation of Cys94 and Ala95 on the central hydrophobic tunnel no longer synthesizd TPI, indicating that Cys94 and Ala95 were essential for forming the dimeric architecture of ultralong-chain TPTs and TPI biosynthesis. A spatiotemporal analysis of the physiological function of TPI in E. ulmoides suggested that it is involved in seed development and maturation. Thus, our analysis provides functional and mechanistic insights into TPI biosynthesis and uncovers biological roles of TPI in plants.

Kajiura and Yoshizawa et al. identify three new prenyltransferases in the tree Eucommia ulmoides that synthesize exceptionally high molecular weight trans-1,4-polyisoprene (TPI). Through crystal structure and mutational analyses, they identify key residues required for TPI synthesis and reveal its functional importance in seed development.

Assessment of Polygala paniculata (Polygalaceae) characteristics for evolutionary studies of legume-rhizobia symbiosis

Root nodule (RN) symbiosis is a mutualistic interaction observed between nitrogen-fixing soil bacteria and nodulating plants, which are scattered in only four orders of angiosperms called nitrogen-fixing clade. Most of legumes engage in RN symbiosis with rhizobia. Molecular genetic analyses with legumes and non-leguminous nodulating plants revealed that RN symbiosis utilizes early signalling components that are required for symbiosis with arbuscular mycorrhizal (AM) fungi. However detailed evolutionary processes are still largely unknown. Comparative analyses with non-nodulating species phylogenetically related to legumes could be better strategies to study the evolution of RN symbiosis in legumes. Polygala paniculata is a non-leguminous species that belongs to a family different from legumes but that is classified into the same order, Fabales. It has appropriate characteristics for cultivation in laboratories: small body size, high fertility and short lifecycles. Therefore, we further assessed whether this species is suitable as a model species for comparative studies with legumes. We first validated that the plant we obtained in Palau was truly P. paniculata by molecular phylogenetic analysis using rbcL sequences. The estimated genome size of this species was less than those of two model legumes, Lotus japonicus and Medicago truncatula. We determined conditions for cultivation in vitro and for hairy root formation from P. paniculata seedlings. It would facilitate to investigate gene functions in this species. The ability of P. paniculata to interact with AM fungi was confirmed by inoculation with Rhizophagus irregularis, suggesting the presence of early signalling factors that might be involved in RN symbiosis. Unexpectedly, branching of root hairs was observed when inoculated with Mesorhizobium loti broad host range strain NZP2037, indicating that P. paniculata has the biological potential to respond to rhizobia. We propose that P. paniculata is used as a model plant for the evolutionary study of RN symbiosis.

Two Eucommia farnesyl diphosphate synthases exhibit distinct enzymatic properties leading to end product preferences

Farnesyl diphosphate synthase (FPS) is an essential enzyme in the biosynthesis of prenyl precursors for the production of primary and secondary metabolites, including sterols, dolichols, carotenoids and ubiquinones, and for the modification of proteins. Here we identified and characterized two FPSs (EuFPS1 and EuFPS2) from the plant Eucommia ulmoides. The EuFPSs had seven highly conserved prenyltransferase-specific domains that are critical for activity. Complementation and biochemical analyses using bacterially produced recombinant EuFPS isoforms showed that the EuFPSs had FPP synthesis activities both in vivo and in vitro. In addition to the typical reaction mechanisms of FPS, EuFPSs utilized farnesyl diphosphate (FPP) as an allylic substrate and participated in further elongation of the isoprenyl chain, resulting in the synthesis of geranylgeranyl diphosphate. However, despite the high amino acid similarities between the two EuFPS isozymes, their specific activities, substrate preferences, and final reaction products were different. The use of dimethylallyl diphosphate (DMAPP) as an allylic substrate highlighted the differences between the two enzymes: depending on the pH, the metal ion cofactor, and the cofactor concentration, EuFPS2 accumulated geranyl diphosphate as an intermediate product at a constant rate, whereas EuFPS1 synthesized little geranyl diphosphate. The reaction kinetics of the EuFPSs demonstrated that isopentenyl diphosphate and DMAPP were used both as substrates and as inhibitors of EuFPS activity. Taken together, the results indicate that the biosynthesis of FPP is highly regulated by various factors indispensable for EuFPS reactions in plants.

Gene coexpression network for trans-1,4-polyisoprene biosynthesis involving mevalonate and methylerythritol phosphate pathways in Eucommia ulmoides Oliver

Eucommia ulmoides, a deciduous dioecious plant species, accumulates trans-1,4-polyisoprene (TPI) in its tissues such as pericarp and leaf. Probable TPI synthase (trans-isoprenyl diphosphate synthase (TIDS)) genes were identified by expressed sequence tags of this species; however, the metabolic pathway of TPI biosynthesis, including the role of TIDSs, is unknown. To understand the mechanism of TPI biosynthesis at the transcriptional level, comprehensive gene expression data from various organs were generated and TPI biosynthesis related genes were extracted by principal component analysis (PCA). The metabolic pathway was assessed by comparing the coexpression network of TPI genes with the isoprenoid gene coexpression network of model plants. By PCA, we dissected 27 genes assumed to be involved in polyisoprene biosynthesis, including TIDS genes, genes encoding enzymes of the mevalonate (MVA) pathway and the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway, and genes related to rubber synthesis. The coexpression network revealed that 22 of the 27 TPI biosynthesis genes are coordinately expressed. The network was clustered into two modules, and this was also observed in model plants. The first module was mainly comprised of MEP pathway genes and TIDS1 gene, and the second module, of MVA pathway genes and TIDS5 gene. These results indicate that TPI is likely biosynthesized by both the MEP and MVA pathways and that TIDS gene expression is differentially controlled by these pathways.

Timing cell-cycle exit and differentiation in oligodendrocyte development

During animal development many cells permanently stop dividing and terminally differentiate. For the most part, the mechanisms that control when the cells exit the cell cycle and differentiate are not known. We have been studying the mechanisms in the oligodendrocyte cell lineage. Studies of oligodendrocyte precursor cells (OPCs) in culture suggest that each OPC has a built-in timing mechanism that helps determine when the cell stops dividing and differentiates. This intrinsic timer consists of at least two components--a timing component, which measures elapsed time, and an effector component, which stops cell division and initiates differentiation at the appropriate time. The timer seems to involve both transcriptional and posttranscriptional mechanisms, with some proteins progressively increasing and others progressively decreasing over time.

A transmembrane trap method for efficient cloning of genes encoding proteins possessing transmembrane domain

To facilitate searching for genes encoding cell membrane proteins, we developed a method for isolating cDNAs that contain sequences for hydrophobic transmembrane runs. This cloning strategy, termed the "transmembrane (TM) trap method," utilizes a vector that directs the cell surface expression of mouse CD4 fusion protein when an insert encoding hydrophobic transmembrane sequences is cloned in-frame with correct orientation. We applied this novel method to isolation of cytokine receptor cDNAs. Our strategy enabled efficient isolation of relatively rare species encoding receptors such as IL-2Rgamma, IL-3Rbeta, IL-4Ralpha, IL-5Ralpha, and IL-6Ralpha. This method also could be used to isolate cDNAs for intracellular molecules with a transmembrane region, e.g., bcl-2. These results indicate that the TM trap method provides an efficient cloning strategy for identification of various families of genes encoding proteins with one or more transmembrane regions.

Role of thyroid hormone receptors in timing oligodendrocyte differentiation

The timing of oligodendrocyte differentiation is thought to depend on both intracellular mechanisms and extracellular signals. Thyroid hormone (TH) helps control this timing both in vitro and in vivo, but it is still uncertain how it does so. TH acts through nuclear receptors that are encoded by two genes, TRalpha and TRbeta. Previous studies suggested that TRbeta receptors may mediate the effect of TH on oligodendrocyte precursor cells (OPCs). Consistent with this possibility, we show here that overexpression of TRbeta1 promotes precocious oligodendrocyte differentiation, whereas expression of two dominant-negative forms of TRbeta1 greatly delays differentiation. Surprisingly, however, we find that postnatal TRbeta-/- mice have a normal number of oligodendrocytes in their optic nerves and that TRbeta-/- OPCs stop dividing and differentiate normally in response to TH in vitro. Moreover, we find that OPCs do not express TRbeta1 or TRbeta2 mRNAs, whereas they do express TRalpha1 and TRalpha2 mRNAs. These findings suggest that alpha receptors mediate the effect of TH on the timing of oligodendrocyte differentiation. We also show that TRalpha2 mRNA, which encodes a dominant-negative form of TRalpha, decreases as OPCs proliferate in vitro and in vivo. This decrease may help control when oligodendrocyte precursors differentiate.

Impaired erythropoiesis in transgenic mice overexpressing a truncated erythropoietin receptor

Erythropoietin (EPO), one of the pivotal regulators of erythrocyte production, transmits signals through the EPO receptor (EPOR). We have previously reported that human bone marrow (BM) cells express two dominant forms of the EPOR, one full-length and one truncated (EPOR-F and EPOR-T). Experiments with a cell line have shown that the EPOR-T acts as a dominant-negative regulator of EPOR-F-mediated signals. Its role in erythropoiesis in vivo, however, has yet to be clarified. Here we show the presence in mouse BM of a truncated form of the EPOR that is essentially the same as EPOR-T in humans. To investigate its role in vivo, we generated transgenic mice overexpressing mouse EPOR-T (EPOR-T-Tg mice). As a result, two independent EPOR-T-Tg lines were established. One line revealed mild anemia, but another line did not. When anemia was induced experimentally in these mice, however, both lines showed apparently poor recovery resulting in higher mortality than wild-type control mice. The impaired erythropoiesis found in these mice thus strongly suggests the EPOR-T's role as a negative regulator of erythropoiesis in vivo.

Role of a truncated erythropoietin receptor for erythroid differentiation

Erythropoietin (EPO) is a cytokine that regulates erythropoiesis through the EPO receptor (EPOR). We reported previously that erythroid progenitor cells express both a full-length and a truncated form of EPOR (EPOR-F and EPOR-Tph). EPOR-Tph cannot transmit growth signals and acts as a dominant negative regulator against EPOR-F-mediated signals for cell survival and growth. Upon transfection of EPOR-F in a cell line, Ba/F3, beta-globin accumulation, which is considered to be a marker of erythroid-differentiation, is inducible in the transformants. We show here that the co-expression of EPOR-Tph in EPOR-F-transformants does not inhibit and rather upregulates the beta-globin induction while inhibiting survival and growth of the transformants. These data suggest that, in contrast to survival and growth signals, EPOR-Tph acts as a positive regulator for erythroid-differentiation signals in erythroid progenitor cells.

Synthesis of N2, N2, 7-trimethylguanosine cap derivatives

Several derivatives of N2,N2-7-trimethylguanosine (m3(2,2,7G)-cap, which was found at the 5' ends of small nuclear RNAs, were synthesized by use of S-phenyl N2,N2,7-trimethylguanosine 5'-phosphorothioate (PhSpm3(2,2,7)G) as a key intermediate. This compound was activated by iodine in the presence of phosphoric acid and diphosphoric acid to give N2,N2,7-trimethylguanosine-5'-diphosphate (ppm3(2,2,7)G) and 5'-triphosphate (ppm3(2,2,7)G), respectively. Similar reactions of PhSpm3(2,2,7)G with ADP and GDP gave capped dinucleoside triphosphates, m3(2,2,7)G5'pppA and m3(2,2,7)G5'pppG, respectively.

Pre-mRNA with a trimethylguanosine cap structure can be spliced efficiently in vitro

A chemically synthesized 2,2,7-trimethylguanosine cap (TMG-cap) analogue was added to an in vitro pre-mRNA splicing system. A slight inhibition of the splicing was observed, but it was much less remarkable than that by a 7-methylguanosine cap analogue. This result does not favor a direct role of the TMG-cap structure of small nuclear RNAs in pre-mRNA splicing, and suggests that the TMG-cap does not effectively interact with the 7-methylguanosine cap binding factors. Using the SP6 in vitro transcription system and a TMG-cap analogue, we prepared a beta-globin transcript which has a TMG-cap at the 5' end. This TMG-capped transcript was spliced accurately and efficiently in vitro.

Expression of the ada gene of Escherichia coli in response to alkylating agents. Identification of transcriptional regulatory elements

Ada protein plays a central role in the regulatory synthesis of DNA repair enzymes, following exposure of Escherichia coli to alkylating agents. Methyl groups of alkylated DNA are transferred to Ada protein by its own methyltransferase activity and the methylated Ada protein then acts as a positive regulator to overproduce the ada and related gene products. To elucidate regulatory mechanisms for the expression of the ada gene by its own product, we analyzed the ada promoter region by random and site-directed mutagenesis. A series of deletion analyses revealed that a sequence up to 53 nucleotides upstream from the transcription initiation site is required for the controlled expression of the ada gene. Libraries of base substitution mutants were constructed by synthesizing oligonucleotides corresponding to the ada promoter region in the presence of a small amount of all possible sets of nucleotides. Internal deletion and insertion mutants were also constructed with the use of synthetic oligonucleotides. Using these mutants, the -10 and the -35 boxes of the promoter as well as the ada regulatory sequence were identified, the latter being an eight-nucleotide sequence, AAAGCGCA. A six-nucleotide stretch between the regulatory sequence and the -35 box, also affected levels of expression of the gene. When the promoter DNAs derived from wild type or base substitution mutants that showed normal expression in vivo were used as templates for transcription in vitro, the ada-specific RNA was formed in the presence of a methylated form of Ada protein. With the DNAs derived from mutants of defective type as templates, no or relatively small amounts of the RNA were synthesized. Some base substitution mutants showed a constitutive expression of the gene in vivo, but this observation did not reconcile with findings in experiments in vitro.

Systematic fractionation of oligosaccharides of human immunoglobulin G by serial affinity chromatography on immobilized lectin columns

Human immunoglobulin G is known to contain 16 different biantennary complex-type asparagine-linked sugar chains, each of which occurs in a nonsialylated, monosialylated, or disialylated form. These oligosaccharides can be separated into 14 fractions by sequential affinity chromatography with Aleuria aurantia lectin (AAL)-Sepharose, RCA120-WG003, and E4-phytohemagglutinin-agarose columns. Twelve of them were found to contain a single oligosaccharide, while the fraction which passed through all three columns was shown to contain two oligosaccharides, GlcNAc beta 1----2Man alpha 1----6(+/- GlcNAc beta 1----4) (GlcNAc beta 1----2Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4GlcNAcOT. The fraction, which bound to the AAL-Sepharose column and passed through the remaining two lectin columns, also contained two oligosaccharides, GlcNAc beta 1----2Man alpha 1----6(+/- GlcNAc beta 1----4) (GlcNAc beta 1----2Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4 (Fuc alpha 1----6)GlcNAcOT. These results indicated that serial affinity chromatography with the three lectin columns can be used effectively to detect changes in the sugar chains of IgG resulting from diseases such as rheumatoid arthritis.

[Clinical usefulness of lymphoscintigraphy by rectal submucosal injection of radioactive colloid]

Lymphoscintigraphies about 27 cases were examined by the methods of 11 cases of anal subcutaneous and 17 cases of rectal submucosal injections of 99mTc-rhenium colloid. Para-aortic nodes and common iliac nodes were visualized in more than 70% out of the 27 cases by these methods, and those images were superior to images obtained by the conventional methods with pedal subcutaneous injections. Internal iliac nodes were visualized in 78.1% by the rectal injection method while in 27.3% by the anal injection method. It was concluded that the transrectal injection method should be used to visualize internal iliac nodes. Examination efficacies of lymphoscintigraphies by these methods on detection of lymph nodes metastases which were confirmed by autopsy, operation, contrast lymphoangiography and/or X-ray CT. As for 131 regions of rectal and anal injected cases, sensitivity was calculated at 84.0% and specificity was at 89.6%. When the cases in which more than one definite defect was detected were scintigraphycally diagnosed as positive to metastasis and when calculated case by case, sensitivity was calculated at 90.9% and specificity was at 62.5% in the 27 cases. Lymphatic systems were seen specifically and systematically by using lymphoscintigraphies. Though the sensitivity was not enough for a screening test of lymph node metastases and the specificity was not enough for a test to rule out lymph node metastases, lymphoscintigraphies are clinically very useful as supplementary examinations. The lymphoscintigraphy by the method of rectal submucosal injection is much more useful as it is convenient and is the only one method to visualize the internal iliac nodes systematically.