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Somatostatins (SS) are a structurally diverse family of peptide hormones that affect various aspects of growth, development and metabolism in vertebrates. Fish have proved to be useful models for understanding the role(s) of SS in the regulation of growth. Organismal growth is inhibited by SS and fish with impaired growth (caused by fasting or premature transfer to seawater of anadromous species) display enhanced SS production and elevated plasma levels of the hormone. Somatostatins modulate growth at the level of the pituitary through the inhibition of growth hormone (GH) synthesis and secretion. There are, however, significant structure-function relationships with regard to GH inhibition. For example, while SS-14 is a potent inhibitor of GH secretion, catfish SS-22 and salmonid SS-25 appear not to have GH secretotropic effects. Somatostatins also have extra-pituitary effects on growth. For example, SS reduce GH binding capacity and inhibit IGF-I mRNA expression in the liver. In addition, SS inhibit insulin, another factor essential to organismal growth. Finally, SS interact with a variety of reproductive and metabolic processes - actions which suggest that SS help modulate energy partitioning among biological processes. [ABSTRACT FROM AUTHOR]

A cDNA clone encoding a cytosolic superoxide dismutase (SOD) was isolated from a cDNA library constructed from poly(A)+RNA from epicotyls of 5-day-old Cicer arietinum L. etiolated seedlings after a differential screening to select clones whose expression decreases with epicotyl growth. Analysis of its deduced amino acid sequence showed all the typical structural motifs of plant cytosolic SODs (EC 1.15.1.1.). The expression of this clone is always higher in young and growing tissues than in old and storage ones, and diminishes throughout the development of the seedlings. Cytosolic Cu/Zn-SOD activity is also higher in radicles and younger internodes. Under stress conditions only cold increases the gene expression whereas the activity is clearly raised up by a saline medium. The results are discussed in relation to the gene regulation and enzyme activity control that crop plants use to resolve the different stresses that reduce their productivity. [Copyright &y& Elsevier]

Cadmium (Cd), a carcinogenic metal in human and rodents, has been shown to transform cells in vitro. However, the carcinogenic mechanisms of Cd as a mutagen and/or promoter are not well clarified. We already reported that CdCl2 in a range of 1.5∼360 ng/ml enhanced transformation of Balb/3T3 A31 cells induced by N-methyl-N′-nitro-N-nitrosoguanidine (MNNG, 0.1 μg/ml) in a dose-dependent manner (Fang et al., Toxicol. In Vitro 15(3) (2001a) 51–7). In previous study, we observed that Cd stimulated cell proliferation on MNNG-initiated cells through inactivation of p53 and p27 and increase of proliferating cell nuclear antigen (PCNA) expression after 24 h treatment (Fang et al., Toxicology 163 (2001b) 175–84). The aim of this study is to further elucidate the long-term effect of Cd in terms of cell cycle control gene expressions during the promotion stage of in vitro two-stage transformation. For the purpose, we determined the expression levels of the genes involved in growth regulation, such as p53, p27, c-myc, mdm2, cyclins D1 and B1, CDK4, and PCNA in the cells treated with Cd for 14 days after MNNG-initiation. In MNNG+CdCl2 group, cells apparently expressed cellular tumor antigen p53 mRNA, but did not express the wild-type p53 protein; the protein and mRNA levels of p27 were reduced apparently in the cells of MNNG+CdCl2 group compared to the cells of control and MNNG group. In addition, the protein levels of cyclin D1, CDK4, PCNA, c-myc, and mdm2, and cyclin B1 mRNA level were higher in MNNG+CdCl2 group than control and MNNG group. Together with previous data (Fang et al., Toxicology 163 (2001b) 175–84), our results indicated that during the transformation process of MNNG-treated cells, Cd may activate oncogenes such as c-myc, mdm2, and cellular tumor antigen p53, inhibit the tumor suppressor genes such as wild-type p53 and p27, and consequently accelerate the proliferation of initiated cells. This work firstly demonstrates that Cd affects the genes involved in growth regulation on initiated cells during the promotion stage of in vitro cell transformation. [Copyright &y& Elsevier]

Recent studies have suggested a role for the Epstein–Barr virus-encoded RNA EBER-1 in malignant transformation. EBER-1 inhibits the activity of the protein kinase PKR, an inhibitor of protein synthesis with tumour suppressor properties. In human 293 cells and murine embryonic fibroblasts, transient expression of EBER-1 promoted total protein synthesis and enhanced the expression of cotransfected reporter genes. However reporter gene expression was stimulated equally well in cells from control and PKR knockout mice. NIH 3T3 cells stably expressing EBER-1 exhibited a greatly increased frequency of colony formation in soft agar, and protein synthesis in these cells was relatively resistant to inhibition by the calcium ionophore A23187. Nevertheless clones containing a high concentration of EBER-1 were not invariably tumourigenic. We conclude that EBER-1 can enhance protein synthesis by a PKR-independent mechanism and that, although this RNA may contribute to the oncogenic potential of Epstein–Barr virus, its expression is not always sufficient for malignant transformation. [Copyright &y& Elsevier]

Transforming growth factor-β (TGF-β) proteins are multifunctional regulators of cell growth and differentiation. The three isoforms, TGF-β1, -β2, -β3 share approximately 70% identical amino acid sequence and are coded by three distinct genes. Growth and differentiation functions in which the isoforms have differential activity include: inhibition of colorectal cancer cell growth, migration of aortic endothelial cells, survival of ciliary ganglionic neurons, and binding to cell surface receptors. A previous paper reported that TGF-β1 and TGF-β2 had bimodal dosedependent stimulatory and inhibitory effects on granulocyte-macrophage colony-stimulating factor induced Day 7 granulocyte-macrophage colony-forming units. The effects of TGF-β3 were only inhibitory. At low concentrations, TGF-β1 and -β2 stimulated growth, whereas at higher concentrations both isoforms inhibited growth. We now report that TGF-β1, TGF-β2, and TGF-β3 are similar to each other at low concentrations; at higher concentrations TGF-β1 and TGF-β3 inhibit growth, but TGF-β2 stimulates growth. Our results are consistent with the known affinities of the TGF-β isoforms with the Type II TGF-β signaling receptor, which has greater affinity for TGF-β1 and TGF-β3 than TGF-β2. [ABSTRACT FROM AUTHOR]

Pectin methylesterases (PMEs) were detected in tobacco (Nicotiana tabacum) pollen tubes grown in vitro. Seven PME isoforms exhibiting a wide isoelectric-point (pI) range (5.3–9.1) were found in crude extracts of pollen tubes. These isoforms were mainly retrieved in supernatants after low- and high-speed separation of the crude extract. Two isoforms, with pIs 5.5 and 7.3 and molecular weight about 158 kDa, were detected by immunoblotting with anti-flax PME antiserum. Localization of pectins and PME isoforms in pollen tubes was investigated by immunogold labelling with JIM5 monoclonal antibodies and anti-flax PME antiserum, respectively. In germinated pollen grains, two PME isoforms were mainly detected in the exine, Golgi apparatus and secretory vesicles. In pollen tubes the same two PME isoforms were distributed along the outer face of the plasma membrane in the vicinity of the inner layer of the cell wall, in the Golgi and around secretory vesicles. In pollen grains, PME isoforms were, in some cases, mixed with acidic pectins in proximity to the outer surface of the plasma membrane. In pollen tubes the presence of PMEs inside secretory vesicles carrying esterified pectins supports the hypothesis that, during pollen tube growth, PMEs could be transferred by secretory vesicles in a precursor form and be activated at the tip where exocytosis takes place. [ABSTRACT FROM AUTHOR]

Data on membrane-bound biochemical mechanisms of control of plant dormancy and resistance to phytopathogens are discussed. Phytohormones are involved in the control of plant dormancy by the modification of activity of membrane-bound enzymes and ion channels. Similar constituents of the plasma membrane are influenced by fungal extracellular metabolites. Proposed interconnections between plasmalemma-bound signaling mechanisms responsible for plant resistance to infection and dormancy regulation are illustrated by a scheme. [ABSTRACT FROM AUTHOR]

The MTW9/PL cell line was established by our laboratory in culture from the carcinogen-induced hormone-responsive MT-W9A rat mammary tumor of a Wistar-Furth (W/Fu) rat. This tumor formed estrogen, androgen, and progesterone responsive tumors in W/Fu rats (Sirbasku, D. A., Cancer Res. 38:1154–1165; 1978). It was later used to derive the MTW9/PL2 cell population which was also estrogen-responsive in vivo (Danielpour, D., et al., In Vitro Cell. Dev. Biol. 24∶42–52; 1988). In the study presented here, we describe serum-supplemented culture conditions in which the MTW9/PL2 cells demonstrate≥80-fold steroid hormone growth responses. All sera used were steroid hormone-depleted by charcoal-dextran treatment at 34°C. The studies were done with horse serum as well as serum from other mammalian species. The growth of the MTW9/PL2 cells was biphasic in response to hormone-depleted serum. Concentrations of ≤5% (v/v) promoted optimum growth. Above this concentration, serum was inhibitory. Concentrations ≥40% (v/v) inhibited growth altogether. Addition of 1.0×10−13−1.0×10−8 M 17β-estradiol (E2) reversed the inhibition completely. At 1.0×10−8 M, estrone, estriol and diethylstilbestrol promoted growth as well as E2. Testosterone and dihydrotestosterone promoted growth only at ≥10−7 M. Progesterone was effective only at≥10−6 M. Cortisol was ineffective. Labeled-hormone-binding analysis and Western immunoblotting documented that MTW9/PL2 cells had estrogen and progesterone receptors but not androgen or cortisol receptors. Estrogen treatment of MTW9/PL2 cells induced a concentration and time dependent increase in progesterone receptors. We conclude (1) the MTW9/PL2 population is the first highly steroid hormone-responsive rat mammary tumor cell line to be established in culture from a carcinogen-induced tumor, and (2) sera from a number of species including horse, rat and human contain an inhibitor which mediates estrogen sensitive MTW9/PL2 cell growth in culture. [ABSTRACT FROM AUTHOR]

The family of human histone genes consists of replication-dependent and independent subtypes. The replication-independent histone genes, also known as variants, give rise to distinct mRNAs, whose expression is regulated depending on the growth state of the cell, tissue type and developmental stage. In turn, the histone variants are differentially synthesized and modified by acetylation. Consequently, chromatin structure is altered resulting in complex changes in gene expression. The high conservation among histone protein subtypes suggests that they are indispensable. In addition, conservation of the positions of acetylation within subtypes suggests that the location of these sites is functionally important for the eukaryotic cell. For example, the structures of transcriptionally active and repressed chromatin are different depending on the acetylation state of histone proteins [1–3]. In addition, transcriptionally active and repressed chromatin contains distinct histone variants [4]. Specialized histone variants are targeted to the centromere of the chromosome, where they are essential for chromosome segregation [5]. Other specialized histones exist that are essential for development [6]. Changes in histone acetylation have been implicated in the down-regulation of a tumour suppressor gene in human breast cancer [7]. Acetylation also plays an important role in X chromosome inactivation as well as hormone-mediated transcriptional regulation [8, 9]. We propose here a novel model for histone variant gene regulation at the post-transcriptional level, which provides the groundwork to define the pathways regulating the synthesis of these variants. [ABSTRACT FROM AUTHOR]

Phyllobacterium brassicacearum STM196, a plant growth-promoting rhizobacterium isolated from roots of oilseed rape, stimulates Arabidopsis growth. We have previously shown that the NRT2.5 and NRT2.6 genes are required for this growth promotion response. Since these genes are members of the NRT2 family of nitrate transporters, the nitrogen assimilatory pathway could be involved in growth promotion by STM196. We address this hypothesis using two nitrate reductase mutants, G5 deleted in the major nitrate reductase gene NIA2 and G′4-3 altered in both NIA1 and NIA2 genes. Both mutants had a reduced growth rate and STM196 failed to increase their biomass production on a medium containing NO3− as the sole nitrogen source. However, they both displayed similar growth promotion by STM196 when grown on an NH4+ medium. STM196 was able to stimulate lateral roots development of the mutants under both nutrition conditions. Altogether, our results indicate that the nitrate assimilatory metabolism is not a primary target of STM196 interaction and is not involved in the root developmental response. The NIA1 transcript level was reduced in the shoots of nrt2.5 and nrt2.6 mutants suggesting a role for this nitrate reductase isoform independently from its role in nitrate assimilation. [ABSTRACT FROM AUTHOR]

Aims: The potential of endophytic Bacillus strains to improve plant growth and yield was evaluated., Methods and Results: Endophytic Bacillus altitudinis HNH7 and Bacillus velezensis HNH9 were evaluated for their growth-promoting traits. In an in vitro plate assay, HNH7 and HNH9 exhibited proteolytic, amylolytic, lipolytic and cellulolytic activity. HNH7 and HNH9 were able to solubilize iron by producing siderophores but were unable to solubilize insoluble phosphate. PCR confirmed the presence of four growth-promoting genes viz. pvd, budA, asbA and satA in the genome of HNH7, while HNH9 also possessed the same genes except for budA. In a greenhouse experiment, HNH7 and HNH9 promoted the growth of upland cotton plants by upregulating the expression of growth-linked genes, EXP6, ARF1, ARF18, IAA9, CKX6 and GID1b. However, the expression of genes involved in ethylene biosynthesis, that is ERF and ERF17 was downregulated after treating the plants with HNH7 and HNH9 compared to the control. Furthermore, cotton plants treated with HNH7 and HNH9 exhibited a significantly higher rate of photosynthesis and stomatal conductance., Conclusion: HNH7 and HNH9 showed a promising potential to promote the growth of cotton plants., Significance and Impact of Study: Research on plant growth-promoting Bacillus strains can lead to the formation of biofertilizers., (© 2022 Society for Applied Microbiology.)

Secondary metabolites, such as phenolic compounds, play an important role in alleviating salinity-induced negative effects in plants. The present study focused on seed priming and foliar application of a potent phenolic compound, coumarin, to induce salinity tolerance in Sorghum bicolor var. SS-77. Based on pilot experiment, 100 mg L -1 concentration of coumarin was applied to mitigate the negative effects of salinity on Sorghum, grown at 0, 100, and 200 mM NaCl under netted greenhouse conditions. Coumarin was applied to each salinity treatment in four different ways (i) non-primed control (NP), (ii) seed priming (COP), (iii) foliar application (COF), and (iv) a combination of seed priming and foliar application (COPF). Salinity stress significantly reduced the plant growth, biochemical attributes, and photosynthetic efficiency of Sorghum, whereas coumarin treatments (COP, COF, and COPF) showed a significant increase (P< 0.01) in above-mentioned parameters at all salinities. Among all, the combined treatment (COPF) showed maximum increase in growth, biochemicals, photosynthetic pigments, antioxidant enzymes, and photosynthetic efficiency parameters. Therefore, it is suggested that a combination of seed priming and foliar spray of 10 mg L -1 coumarin is more suitable than their individual applications. It is an environment friendly and economically feasible approach that will be used to improve salinity tolerance of Sorghum and helpful to get considerable biomass from saline degraded lands to fulfill food, fodder, and energy demands of the ever-growing population., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Sultana, Wang, Azeem, Hussain, Mahmood, Fiaz and Qasim.)

flbA encodes an Aspergillus nidulans RGS (regulator of G protein signaling) domain protein that antagonizes FadA (Giα-subunit of heterotrimeric G protein)-mediated growth signaling to allow asexual development. We previously defined and characterized five suppressors of flbA (sfa) loss-of-function mutations and showed that one suppressor (sfaB) resulted from a novel dominant-negative allele of fadA. In this report we show that a second suppressor gene (sfaD) is predicted to encode the β subunit of a heterotrimeric G protein. Deletion of sfaD suppressed all defects resulting from complete loss-of-flbA function mutations, caused a hyperactive sporulation phenotype and severely reduced vegetative growth. However, the sfaD deletion could not suppress the growth activation caused by dominant-activating fadA alleles, indicating that constitutively active FadA can cause proliferative growth in the absence of Gβγ signaling. We propose that SfaD and FadA are both positive growth regulators with partially overlapping functions and that FlbA has an important role in controlling the activities of both proteins. Inactivation of signaling events stimulated by both components of the heterotrimeric G protein is essential for both sexual and asexual sporulation. [ABSTRACT FROM AUTHOR]

We established a monoclonal antibody, 3G12 (IgG1), with antiproliferative effects on a human T-cell leukaemia cell line, SUP-T13. Among haematolymphoid cell lines, 3G12 reacted with most T-cell lines, Epstein-Barr transformed B-cell lines, some myelomonocytic cell lines and, most strongly with an anaplastic large cell lymphoma (ALCL) cell line, Karpas 299. The cell panel reactive with 3G12 was similar, but not identical, to that of the anti-CD30 antibody Ber-H2. 3G12 induced Fas-independent apoptosis in SUP-T13 and it also induced growth-inhibition in a limited number of other cell lines, but not Karpas 299. Immunohistochemical studies on paraffin-embedded tissue specimens demonstrated that 3G12 reacted with most CD30-positive ALCL cases and some T-cell lymphomas and some Hodgkin's lymphomas, but not with B-cell lymphomas or non-haematogeneic tumours. The immunoprecipitation study with 3G12 demonstrated a major band of 200 kD and a minor band of 100 kD, which were different from CD30. Thus 3G12 defines a novel antigen that shares a similarity to CD30 in terms of distribution among haemopoietic cells. The data suggest that the 3G12-defined antigen, designated Hal-1, is important as a marker for ALCL and may play a role in its pathogenesis. [ABSTRACT FROM AUTHOR]

The natural estrogen 17β-estradiol (E2) functions as a potent tumor promoter during tumorigenic transformation of the mammary gland. From amongst the various pathways of E2 metabolism upregulation of C16α-hydroxylation of E2 has been associated with carcinogenesis. In the present study in vitro and in vivo experiments were performed on estrogen receptor positive human breast cancer MCF-7 cells to examine whether the natural estrogen E2 and its metabolites 16α-hydroxyestrone (16α-OHEi) and 2-hydroxyestrone (2-OHE1) function as modulators of tumor cell growth. An anchorage-independent growth assay was used for in vitro study by counting the number of tri-dimensional colonies formed by MCF-7 cells suspended in 0.33% agar. In vivo experiments examined the effect of implanting metabolite material pellets into female nude mice. In the anchorage-independent growth assay (AIG), continuous 14-day exposure to E2 and to 16α-OHE1 at 200 ng/ml induced a 59.4% and a 105.9% increase (P=0.001) respectively in the number of colonies of MCF-7 cells. Identical treatment with 2-OHE1, however, failed to increase AIG relative to that seen in the solvent treated control cultures. In the in vivo tumorigenicity assay, treatment of nude mice with 1.5 mg E2 or 16α-OHE1 resulted in a 335.4% and a 384.1% increase (P<0.0002) in tumor growth, while identical treatment with 2-OHE1 failed to exhibit any increase relative to the control group. These results suggest that the 16α- and 2-hydroxylated metabolites of E2 may directly affect in vitro growth of MCF-7 cells via an autocrine mechanism and in vivo growth via paracrine mechanisms. Thus, E 2-mediated growth regulation in MCF-7 cells may in part be due to distinct effects of specific E2 metabolites on the breast cancer cells. [ABSTRACT FROM AUTHOR]

Oligosaccharides that exert biological effects on higher plants (other than as carbon or energy sources) have been termed 'oligosaccharins'. A limited number of specific oligo-β-glucans derived from fungal cell walls exhibit oligosaccharin activity, at very low doses, switching on the synthesis of phytoalexins. The structural requirements lot this biological activity ate stringent, and there is strong evidence that the oligosaccharins of fungal origin act through a receptor in the plant cell membrane Chemically unrelated oligosaccharins can also be produced by partial digestion of pectins and xyloglucans born higher plant cell walls. In some cases, for example, the α-L-fucosylated oligoxyloglucans that antagonise the growth-promoting effect of auxin, these plant-derived oligosaccharins have relatively strict structural requirements for activity and act at ∼10-6 mol m-3; these may act via specific receptors. In other cases, for example, the growth-promoting action of other oligoxyloglucans, the stringency is somewhat lower and the activity is only seen at ∼10-3 mol m-3, and these oligosaccharins ate proposed to influence growth through their ability to modulate the activity of an enzyme, cellulase. A thrid class of plant-derived oligo-saccharins, the oligo-α-galacturonides, appear to have much less stringent structural requirements; a number of unrelated physiological responses are evoked by the same range of oligo-α-galacturonides at ∼10-3 to 1 mol m-3. We suggest that these oligosaccharins may act via a mechanism not involving a specific receptor, perhaps by interacting with the plasma membrane to bring about a change in its physical properties [ABSTRACT FROM AUTHOR]

We tested the hypothesis that electrogenic ion pumps, working at the parenchyma symplast/xylem interface of pea hypocotyls, provide the driving force for K+ uptake from the xylem. Solutions of known composition were perfused through a hypocotyl segment. The K+ activity of the solution flowing out of the xylem (K+out) increased (i.e. K+ uptake decreased) when aerobic respiration was inhibited by lack of O2, and this was preceded by a decrease in Vpx (electrical potential difference between parenchyma symplast and xylem). Perfusion with auxin (IAA) and fusicoccin (FC) stimulated the electrogenic activity of the 'xylem pumps' (111 and 205% respectively) and stimulated uptake of K+ from the xylem (with 71% and 29% respectively). The close correlation between xylem pump activity and K+ uptake corroborated the aforementioned hypothesis. Interestingly, inhibition of pump activity by anoxia was incomplete in the presence of FC. It is thought that FC increases the affinity of the ATP-requiring xylem pump for ATP, thus ensuring that ATP production during fermentation is sufficient to fuel the pump in the absence of O2. [ABSTRACT FROM AUTHOR]

The expression of a transgene coding for a chimeric molecule, containing the cytoplasmic and transmembrane domains of the β1-integrin chain and the extracellular domain of the T-cell differentiation antigen CD4, was targeted to the mouse mammary gland by the mouse mammary tumor virus (MMTV) promoter. The chimera does not interact with the extracellular ligands; however, its expression in cultured cells was shown to interfere with focal adhesion kinase (FAK) phosphorylation following ligation of endogenous β1-integrin. Therefore, expression of the transgenic protein on the cell surface should uncouple adhesion from intracellular events associated with the β1-cytoplasmic domain and thus perturb β1-integrin functions. Although most of the transgenic females were able to lactate, their mammary glands had a phenotype clearly distinct from that of wild-type mice. At mid-pregnancy and the beginning of lactation, transgenic glands were underdeveloped and the epithelial cell proliferation rates were decreased, while the apoptosis levels were higher than in wild-type glands. In lactation, the amounts of the whey acidic protein (WAP) and β-casein gene transcripts were diminished, and the basement membrane component, laminin and the β4-integrin chain accumulated at the lateral surface of luminal epithelial cells, revealing defects in polarization. Our observations prove that in vivo, β1-integrins are involved in control of proliferation, apoptosis, differentiation and maintenance of baso­apical polarity of mammary epithelial cells, and therefore are essential for normal mammary gland development and function. [ABSTRACT FROM AUTHOR]

The myrosinase‐glucosinolate system is involved in a range of biological activities affecting herbivorous insects, plants and fungi. The system characteristic of the order Capparales includes sulphur‐containing substrates, the degradative enzymes myrosinases, and cofactors. The enzyme‐catalyzed hydrolysis of glucosinolates initially involves cleavage of the thioglucoside linkage, yielding D‐glucose and an unstable thiohydroximate‐O‐sulphonate that spontaneously rearranges, resulting in the production of sulphate and one of a wide range of possible reaction products. The products are generally a thiocyanate, isothiocyanate or nitrile, depending on factors such as substrate, pH or availability of ferrous ions. Glucosinolates in crucifers exemplify components that are often present in food and feed plants and are a major problem in the utilization of products from the plants. Toxic degradation products restrict the use of cultivated plants, e.g. those belonging to the Brassicaceae. The myrosinase‐glucosinolate system may, however, have several functions in the plant. The glucosinolate degradation products are involved in defence against insects and phytopathogens. and potentially in sulphur and nitrogen metabolism and growth regulation. The compartmentalization of the components of the myrosinase‐glucosinolate system and the cell‐specific expression of the myrosinase represents a unique plant defence system. In this review, we summarize earlier results and discuss the organisation and biochemistry of the myrosinase‐glucosinolate system. [ABSTRACT FROM AUTHOR]

Seedlings of maize (Zea mays L. cv. Golden Cross Bantam T-51) were grown under microgravity conditions simulated by a three-dimensional clinostat. On the clinostat, maize shoots exhibited curvatures in three different portions: (1) the basal transition zone connecting roots and mesocotyls, (2) the coleoptile node located between mesocotyls and coleoptiles, and (3) the elongating region of the coleoptiles. Even nonclinostatted control shoots showed some degree of curvature away from the caryopsis in the transition zone and bending toward the caryopsis in the coleoptile node. Clinostat rotation greatly stimulated these curvatures. Control coleoptiles elongated almost straightly, whereas coleoptiles on the clinostat bent either away from or toward the caryopsis depending on the timing of rotation. The curvature in all three portions became larger with time, both in control and clinostatted seedlings. There was no difference in the osmotic concentration of the cell sap between the convex and the concave halves of any portion. However, in coleoptile nodes and coleoptiles, the faster-expanding convex side exhibited a higher extensibility of the cell wall than the opposite side, and this appears to be a cause of the curvature. Thus, changes in the cell wall metabolism may be involved in automorphosis, which governs the life cycle of plants under a microgravity environment. [ABSTRACT FROM AUTHOR]

Auxin-induced elongation of epicotyl segments of azuki bean (Vigna angularis Ohwi et Ohashi cv. Takara) was suppressed by a fucose-binding lectin from Tetragonolobus purpureas Moench and by polyclonal antibodies raised against xyloglucan heptasaccharide (Xyl3Glc4) when the cuticle present in the outer surface of epicotyls was abraded. In contrast, elongation of non-abraded segments was not influenced by the lectin or the antibodies. Epicotyl segments, from which the epidermal and the outer cortical cells had been removed, elongated rapidly for 2 h and then only slowly. Auxin slightly stimulated elongation of the inner tissue segments in the phase of slow growth. Neither in the presence nor in the absence of auxin did the lectin or the antibodies affect elongation of the inner tissue segments. The split portions of outer surface-abraded epicotyl segments incubated in buffer extended outward, and auxin inhibited this outward bending. The lectin and the antibodies reversed the effect of auxin on bending. The fucose-binding lectin pretreated with fucose or the immunoglobulin fraction obtained from preimmune serum exhibited little or no inhibitory effect on auxin-induced elongation of abraded or split segments. These results support the view that a breakdown of xyloglucans in the epidermal cell walls plays an essential role in auxin-induced elongation in dicotyledons. [ABSTRACT FROM AUTHOR]

Besides being applied in agriculture and horticulture, the new types of plant growth retardants from norbornanodiazetine, triazole, pyrimidine, 4-pyridine and imidazole structure are increasingly used in physiological research. As inhibitors of special cytochrome P-450 dependent monooxygenases they allow valuable insights in the regulation of terpenoid metabolism concerning phytohormones and sterols, thus showing relations to cell division, cell elongation and senescence. [ABSTRACT FROM AUTHOR]

Indole-3-acetic acid and 1-aminocyclopropane-1-carboxylic acid, the precursor of ethylene, stimulated elongation of coleoptiles of seedlings of intact rice (Oryza sativa L. cv. Sasanishiki) submerged in buffer solution with constant air-bubbling. The osmotic pressure of the cell sap decreased during elongation of coleoptiles. In the presence of 30 µM aminooxyacetic acid, an inhibitor of ethylene biosynthesis, indole-3-acetic acid at 30 µM accelerated the decrease in the osmotic pressure in the early stage of growth. 1-Aminocyclopropane-1-carboxylic acid at 30 µM did not influence the decrease in the osmotic pressure. Both indole-3-acetic acid and 1-aminocyclopropane-1-carboxylic acid decreased the minimum stress-relaxation time and the relaxation rate of the cell wall, suggesting that both auxin and ethylene induce elongation of rice coleoptiles by stimulating cell wall loosening. These growth regulators caused an increase in the level of glucose in hemicelluloses in the early stage of growth and a decrease in the level in the subsequent fast growth phase. Indole-3-acetic acid decreased the hydroxyproline and glucosamine levels per unit dry weight of the cell wall. These changes in the level of cell wall components may be associated with the changes in the mechanical properties of the cell walls caused by auxin and ethylene. [ABSTRACT FROM AUTHOR]

Antiserum raised against the LiCl extract of maize shoot cell walls suppresses auxin-induced elongation of maize coleoptile segments. A series of polyclonal antibodies were raised against protein fractions separated from the LiCl extract of maize (Zea mays L. cv. B73 × Mo17) coleoptiles by SP-Sephadex and Bio-Gel P-150 chromatography. To understand the role of cell wall proteins in growth regulation, the effect of these antibodies on auxin-induced elongation and changes in the cell walls of maize coleoptiles was examined. Four of the fractions prepared reacted with the antiserum raised against the total LiCl extract and effectively suppressed its growth-inhibiting activity. Only these fractions contained the proteins responsible for eliciting growth-inhibiting antibodies. The antibodies capable of growth inhibition of auxin-induced elongation of segments also inhibited auxin-induced cell wall loosening (decrease in the minimum stress-relaxation time of the cell walls) of segments. The antibodies raised against one of the protein fractions separated by SP-Sephadex inhibited the autolytic reactions of isolated cell walls and the auxin-induced decrease in (1→3), (1→4)-β-D-glucans in the cell walls. Thus, the degradation of β-D-glucans by cell wall enzymes may be associated with the cell wall loosening that is responsible for cell elongation. Because the other antibodies did not influence the auxin-induced degradation of (1→3), (1→4)-β-D-glucans, β-D-glucanases and other cell wall enzymes may cooperate in regulation of cell elongation in maize coleoptiles. [ABSTRACT FROM AUTHOR]

Auxin-induced elongation of coleoptile segments of oat (Avena sativa L. cv. Victory) was suppressed by agglutinin from Canavalia ensiformis DC. (concanavalin A), Triticum vulgaris Vill. germ, Dolichos biflorus L., Glycine max Merr. and Limulus polyphemus L. at 0.5 mg ml-1, while that of epicotyl segments of azuki bean (Vigna angularis Ohwi and Ohashi cv. Takara) was suppressed by agglutinin from Canavalia ensiformis DC., Tetragonolobus purpureus Moench and Ulex europaeus L. I when segments were incubated at pH 6.0. These lectins suppressed elongation without any prominent lag period. This suppression of elongation by the lectins was not apparent at pH 4.0. When a ligand for lectins, for instance methyl-α-D-mannopyranoside, was added simultaneously with the lectin, elongation of segments was completely or partly restored. The lectins that suppressed elongation were bound to the cell walls of the segments and inhibited the auxin-induced cell wall loosening (decrease in the minimum stress-relaxation time of the cell wall). Thus, the lectins may, at least partly, suppress elongation by inhibiting cell wall loosening. Our results demonstrate that the wall components containing a-z-mannose (α-D-glucose), N-acetyl-D-glucosamine, N-acetyl-D-galactosamine or D-glucuronic acid play an important role in wall loosening of oat coleoptiles, while the wall components containing α-D-mannose (α-D-glucose) or L-fucose are important for that of azuki epicotyls. [ABSTRACT FROM AUTHOR]