Association of actin with alpha crystallins

The alpha crystallins are cytosolic proteins that co-localize and co-purify with actin-containing microfilaments. Affinity column chromatography employing both covalently-coupled actin or alpha crystallin was used to demonstrate specific and saturable binding of actin with alpha crystallin. This conclusion was confirmed by direct visualization of alpha aggregates bound to actin polymerized in vitro. The significance of this interaction in relation to the functional properties of these two polypeptides will be discussed.     

Field measurements of nitrogen-fixing activity of intact saplings ofAlnus maximowiczii in the subalpine zone of Mt Fuji

Nitrogen-fixing (acetylene-reducing) activity of intact saplings ofAlnus maximowiczii was measured under natural conditions in the subalpine zone of Mt Fuji. The nitrogen-fixing activity was detected from the middle of June when expansion of leaves had just begun to the end of October when the shedding of leaves was almost completed. Diurnal changes in the activity were almost parallel with those of ground temperature. The measured nitrogen-fixing activity was related to ground temperature and total leaf area. Using this relation, annual nitrogen fixation was estimated from the data of ground temperature and leaf area measured in the field. The amount of annual nitrogen fixation was almost the same as that of nitrogen used for annual growth. It was concluded that nitrogen fixation by nodules made a considerable contribution to the nitrogen economy in the saplings ofA. maximowiczii.     

Involvement of Cell Wall-Bound Diferulic Acid in Light-Induced Decrease in Growth Rate and Cell Wall Extensibility of Oryza Coleoptiles

Irradiation of white fluorescent light (5 W m^–2) inhibitedthe growth of Oryza coleoptiles. Light irradiation increasedstress-relaxation parameters of coleoptile cell walls, minimumstressrelaxationtime and relaxation rate, and decreased cellwall extensibility (strain/load). Under light conditions, thecontents of ferulic and diferulic acids ester-linked to thehemicellulosic arabinose residue in cell walls increased andcorrelated with the modification of the cell wall mechanicalproperties. These results suggest that light irradiation enhancesthe formation of diferulic acid bridges in hemicelluloses, makingcell walls mechanically rigid and thus inhibits cell elongationin rice coleoptiles. Also, irrespective of coleoptile age orthe presence of light, the ratio of diferulic acid to ferulicacid was almost constant, suggesting that the rate limitingstep in the formation of diferulic acid bridges in Oryza cellwalls is in the step of feruloylation. (Received September 24, 1991; Accepted December 3, 1991)     

Predation impact of Leptodora kindtii on population dynamics and morphology of Bosmina fatalis and B. longirostris in mesocosms

1. We assessed the impact of predation by the invertebrate predator Leptodora kindtii on Bosmina longirostris and B. fatalis, which show seasonal and reciprocal succession patterns in Lake Suwa, in a mesocosm experiment using 20‐L tanks with or without the predator under different food conditions. We also analysed morphological responses of the two Bosmina species to the predator in the tanks. 2. Bosmina fatalis dominated B. longirostris regardless of predator presence under high food density. However, the presence of Leptodora induced the dominance of B. fatalis more rapidly than its absence. On the contrary, no dominance of B. fatalis was observed in tanks with low food density, irrespective of the presence of the predator. Only B. fatalis showed morphological changes in response to the presence of Leptodora. 3. Mucrone length and antennule shape (angle between body and antennule and angle between antennules) showed marked responses at both high and low food densities, but antennule length responded only at high food density. Mucrone length seems to be a more effective defence against Leptodora. 4. The results suggest that B. fatalis is a superior competitor against B. longirostris and is more resistant to Leptodora predation, especially in good food conditions. The repeatedly observed seasonal succession of the two Bosmina species in the eutrophic Lake Suwa – the replacement of B. longirostris by B. fatalis following the occurrence of abundant Leptodora– seems to be caused by the selective predation of Leptodora on B. longirostris as well as the competitive ability of B. fatalis.     

Gravity resistance, another graviresponse in plants--function of anti-gravitational polysaccharides]

The involvement of anti-gravitational polysaccharides in gravity resistance, one of two major gravity responses in plants, was discussed. In dicotyledons, xyloglucans are the only cell wall polysaccharides, whose level, molecular size, and metabolic turnover were modified under both hypergravity and microgravity conditions, suggesting that xyloglucans act as anti-gravitational polysaccharides. In monocotyledonous Poaceae, (1-->3),(1-->4)-beta glucans, instead of xyloglucans, were shown to play a role as anti-gravitational polysaccharides. These polysaccharides are also involved in plant responses to other environmental factors, such as light and temperature, and to some phytohormones, such as auxin and ethylene. Thus, the type of anti-gravitational polysaccharides is different between dicotyledons and Poaceae, but such polysaccharides are universally involved in plant responses to environmental and hormonal signals. In gravity resistance, the gravity signal may be received by the plasma membrane mechanoreceptors, transformed and transduced within each cell, and then may modify the processes of synthesis and secretion of the anti-gravitational polysaccharides and the cell wall enzymes responsible for their degradation, as well as the apoplastic pH, leading to the cell wall reinforcement. A series of events inducing gravity resistance are quite independent of those leading to gravitropism.     

Concanavalin A Inhibits Auxin-Induced Elongation and Breakdown of (1 -> 3), (1 -> 4)-{beta}-D-Glucans in Segments of Rice Coleoptiles

Concanavalin A (Con A) suppresses auxin-induced elongation ofsurface-abraded segments from both dicotyledonous and poaceousplants. In coleoptile segments of rice (Oryza sativa L.), theauxin-induced decrease in the minimum stress-relaxation timeand increase in the mechanical extensibility of the cell wallswere also inhibited by Con A, indicating that the lectin suppresseselongation by inhibiting the cell wall loosening. Auxin causeda decrease in the level of (1 3), (1 4)-ß-D-glucansin the cell walls of rice coleoptile segments, and this decreasewas also inhibited by the lectin. Con A suppressed the autolytichydrolysis of the glucans, as well as their breakdown in vitroby a protein fraction that had been extracted from the cellwalls of rice coleoptiles with 1 M NaCl. Furthermore, most ofthe glucan-hydrolyzing activity of the wall proteins bound toa Con A-Sepharose column, suggesting that glycoprotein enzymesare involved in the hydrolysis. Although Con A also affectedthe hydrolysis of other wall polysaccharides, the present data,when considered in combination with the inhibitory effects ofglucan-specific or glucanasespecific antibodies, support theview that the breakdown of (1 3),(1 4)-ß-D-glucansis associated with the cell wall loosening that is responsiblefor auxin-induced elongation in Poaceae. (Received August 17, 1994; Accepted February 15, 1995)     

Purification and characterization of the Pseudomonas aeruginosa NfxB protein, the negative regulator of the nfxB gene.

The protein NfxB, involved in conferring resistance to quinolones in Pseudomonas aeruginosa, has a helix-turn-helix motif which is similar to that of other DNA-binding proteins. It appears to affect the membrane-associated energy-driven efflux of some antibiotics (H. Nikaido, Science 264:382-388, 1994). We constructed a plasmid that overproduced NfxB in Escherichia coli and purified the protein. Two species of NfxB (23 and 21 kDa), which are probably translated from different initiation codons, were isolated. Both proteins are also expressed in vivo in P. aeruginosa, with the 23-kDa NfxB being the major species. NfxB specifically binds upstream of the nfxB coding region as demonstrated by gel retardation and DNase I footprinting. Expression of the phi (nfxB'-lacZ+) (Hyb) gene was repressed in the presence of the nfxB gene product provided by a second compatible plasmid in E. coli. In the P. aeruginosa wild-type strain (PAO2142), NfxB was undetectable by immunoblotting; however, it was detected in the nfxB missense mutant (PK1013E). These results suggested that NfxB negatively autoregulates the expression of nfxB itself. Since the 54-kDa outer membrane protein (OprJ) (N. Masuda, E. Sakagawa, and S. Ohya, Antimicrob. Agents Chemother. 39:645-649, 1995) was overproduced in nfxB mutants, NfxB may also regulate the expression of membrane proteins that are involved in the drug efflux machinery of P. aeruginosa.     

Control of trophoblast cell differentiation: Lessons from the genetics of early pregnancy loss and trophoblast neoplasia

Trophoblast cell differentiation is crucial to the morphogenesis of the placenta and thus the establishment of pregnancy and the growth and development of the embryo/fetus. In the present review, we discuss current evidence for the existence of regulatory genes crucial to trophoblast cell differentiation and placental morphogenesis. The elucidation of regulatory pathways controlling normal differentiation of trophoblast cells will facilitate the identification of sensitive junctures in the regulatory pathways leading to various developmental disorders, including those associated with the initiation of pregnancy, fetal growth retardation and gestational trophoblast disease.     

Effect of Temperature on Pratylenchus penetrans Development

Reproduction and development of Pratylenchus penetrans were studied on genetically transformed ladino clover roots. Solitary females developing on transformed roots in nutrient gellan gum medium (pH 5.5) deposited 1.2, 1.5, 1.6, 1.8, and 2.0 eggs per day at the respective temperatures of 17, 20, 25, 27, and 30 °C. The number of eggs deposited was highly correlated with temperature. A reduction in egg-laying rates at the start of hatching was observed at all temperatures. Juvenile mortality was higher at 17 °C (50.4%), 20 °C (50.3%), and 30 °C (58.4%) than at 25 °C (34.6%) and 27 °C (37.6%). Life-cycle (egg deposition to egg deposition) duration was 46, 38, 28, 26, and 22 days at the respective temperatures. The developmental zero degrees (°C) and the effective accumulative temperatures (degree-days) required for hatching, female emergence, and onset of oviposition (completion of one generation) of P. penetrans were estimated to be 2.7 and 200, 4.2 and 548, and 5.1 and 564, respectively. Pratylenchus penetrans reproduces over a wide range of temperatures.