A single treatment of rice seedlings with 5-azacytidine induces heritable dwarfism and undermethylation of genomic DNA

Summary A single exposure of germinated rice seeds (Oryza sativa) to either of the DNA demethylating agents 5-azacytidine (azaC) or 5-azadeoxycytidine (azadC) induced dwarf plants. At maturity, seeds treated with azaC exhibited normal morphological characteristics in comparison with untreated controls except that their height (total stem length) was reduced by about 15%. The M₁ progeny, obtained by self-fertilization of an azaC-induced dwarf plant, segregated into dwarf (35%) and apparently tall types (65%). The M₂ progenies, obtained by self-fertilization of dwarf M₁ plants, were also dwarf, while those from tall M₁ plants were only tall. Genomic DNA isolated from mature leaves of azaC-treated seeds showed about a 16% reduction in the 5-methylcytosine (m⁵C) content in comparison with DNA from untreated samples. A similar reduction in the m⁵C content was also observed in the M₁ and M₂ progenies. Thus, both undermethylation and dwarfism induced by azaC treatment were heritable. The results suggest that azaC induced demethylation of genomic DNA, which caused an altered pattern of gene expression and consequently a reduction in plant stem length.     

Possible Mechanism of Action of β-Lactam-Enhancing Factor on Methicillin-Resistant Staphylococcus aureus

We have recently found a factor (Factor T) in aged mixtures of tungstate and phosphate which greatly enhances the antibacterial effects of β-lactams on methicillin-resistant strains of staphylococcal species such as methicillin-resistant Staphylococcus aureus (MRSA), but shows only weak effects on methicillin-susceptible S. aureus and bacterial strains other than staphylococci. Factor T alone did not strongly inhibit cell metabolism and bacterial growth unless an excess amount was added. When Factor T was added to the culture medium beforehand, the growth of MRSA cells was rapidly suppressed just after addition of oxacillin (MPIPC). However, the growth of the cells was inhibited gradually when these two reagents were added in reverse order. For full expression of the enhancing effect, it seemed necessary for cells of MRSA strains to be incubated with Factor T for at least 2–3 hr. When the cells were washed after being sensitized by incubating them for 5 hr with Factor T, it took approximately 1 hr for the cells to recover their resistance to MPIPC. Factor T reduced the amount of penicillin-binding protein-2′ (PBP 2′), and thus sensitized the MRSA strains to β-lactams.     

Polymerization and depolymerization of actin with nucleotide states at filament ends

Polymerization induces hydrolysis of ATP bound to actin, followed by γ-phosphate release, which helps advance the disassembly of actin filaments into ADP-G-actin. Mechanical understanding of this correlation between actin assembly and ATP hydrolysis has been an object of intensive studies in biochemistry and structural biology for many decades. Although actin polymerization and depolymerization occur only at either the barbed or pointed ends and the kinetic and equilibrium properties are substantially different from each other, characterizing their properties is difficult to do by bulk assays, as these assays report the average of all actin filaments in solution and are therefore not able to discern the properties of individual actin filaments. Biochemical studies of actin polymerization and hydrolysis were hampered by these inherent properties of actin filaments. Total internal reflection fluorescence (TIRF) microscopy overcame this problem by observing single actin filaments. With TIRF, we now know not only that each end has distinct properties, but also that the rate of γ-phosphate release is much faster from the terminals than from the interior of actin filaments. The rate of γ-phosphate release from actin filament ends is even more accelerated when latrunculin A is bound. These findings highlight the importance of resolving structural differences between actin molecules in the interior of the filament and those at either filament end. This review provides a history of observing actin filaments under light microscopy, an overview of dynamic properties of ATP hydrolysis at the end of actin filament, and structural views of γ-phosphate release.     

A standard protocol for documenting modern and fossil ichnological data

The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary researchers, and to future generations. Primarily, our aim is to make the 3D capture of ichnological data standard practice, and to provide guidance on how such 3D data can be communicated effectively (both via the literature and other means) and archived openly and in perpetuity. We recommend capture of 3D data, and the presentation of said data in the form of photographs, false‐colour images, and interpretive drawings. Raw data (3D models of traces) should always be provided in a form usable by other researchers (i.e. in an open format). If adopted by the field as a whole, the result will be a more robust and uniform literature, supplemented by unparalleled availability of datasets for future workers.     

Survival strategy of the salt-tolerant lactic acid bacterium,Tetragenococcus halophilus,to counteract koji mold,Aspergillus oryzae,in soy sauce brewing

In soy sauce brewing, the results of the fermentation of lactic acid greatly affect the quality of soy sauce. The soy sauce moromi produced with Aspergillus oryzae RIB40 allows the growth of Tetragenococcus halophilus NBRC 12172 but not T. halophilus D10. We isolated and identified heptelidic acid (HA), an inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), produced by A. oryzae RIB40 as the growth inhibitor of the salt-tolerant lactic acid bacteria. The growth inhibition of T. halophilus D10 by HA was suggested to be associated with the direct inhibition of GAPDH activity under high salt environment. The difference in the susceptibility to HA among various strains of T. halophilus was caused by the mutations in the gene encoding GAPDH.     

Latrunculin A Accelerates Actin Filament Depolymerization in Addition to Sequestering Actin Monomers

1. Download high-res image (220KB)
2. Download full-size image

     

Effects of Light Stress on Redox Potential Forms of Cyt b-559 in Photosystem II Membranes Depleted of Water-Oxidizing Complex

Effects of photoinhibition on the redox properties of Cyt b-559were studied with NH₂OH treated PSII membranes, which are depletedof the water-oxidizing complex. The membranes contained threeredox forms (HP-, IP- and LP-forms) of Cyt b-559, with E_m valuesof +435, +237 and +45 mV, respectively. A novel intermediate-potentialform of Cyt b-559 was generated during photoinhibition on thedonor side of PSII: photoinhibitory illumination (7,000 µEm^–2 s^–1) for 1 min induced a 30% decrease in thelevel of the HP-form, with concomitant generation of the intermediate-potential(IP-) form whose E_m value was about +350mV. Prolonged illumination(10 min) resulted in complete loss of the HP-form and an apparentincrease in the level of the IPform. After further photoinhibitorytreatment (60 min), complete loss of the IP'-form was observedand levels of the IP- and LP-forms each increased to about 50%of the total amount of Cyt b-559. Kinetic analysis of thesedata led to the conclusion that the HP-form is converted tothe LP-form via two intermediate-potential forms (IP' and IP),and that IP'-form appears only at the early phase of photoinhibition. (Received March 30, 1994; Accepted February 27, 1995)