Nucleotide sequence of the genome of the filamentous bacteriophage I2-2: Module evolution of the filamentous phage genome

Summary The nucleotide sequence of the circular single-stranded genome of the filamentous Escherichia coli phage I2-2 has been determined and compared with those of the filamentous E. coli phages Ff(M13, fl, or fd) and IKe. The I2-2 DNA sequence comprises 6744 nucleotides; 139 nucleotides less than that of the N- and I2-plasmid-specific phage IKe, and 337 (336) nucleotides more than that of the F-plasmid-specific phage Ff. Nucleotide sequence comparisons have indicated that I2-2, IKe, and Ff have a similar genetic organization, and that the genomes of I2-2 and IKe are evolutionarily more closely related than those of I2-2 and Ff. The studies have further demonstrated that the I2-2 genome is a composite replicon, composed of only two-thirds of the ancestral genome of IKe. Only a contiguous I2-2 DNA sequence of 4615 nucleotides encompassing not only the coat protein and phage assembly genes, but also the signal required for efficient phage morphogenesis, was found to be significantly homologous to sequences in the genomes of IKe and Ff. No homology was observed between the consecutive DNA sequence that contains the origins for viral and complementary strand replication and the replication genes. Although other explanations cannot be ruled out, our data strongly suggest that the ancestor filamentous phage genome of phages I2-2 and IKe has exchanged its replication module during evolution with that of another replicon, e.g., a plasmid that also replicates via the so-called rolling circle mechanism. Offprint requests to: R.N.H. Konings     

Pulse-modulated photoacoustic measurements reveal strong gas-uptake component at high CO2-concentrations

The effect of high CO₂-concentration on photoacoustic signals from tobacco leaves is studied by means of a recently developed pulse modulation method which provides simultaneous information on photothermal and photobaric components in the millisecond time domain. High CO₂-concentrations are found to induce large gas-uptake signals. Simultaneous measurements of chlorophyll fluorescence suggest that the uptake signals are correlated with energy-dependent fluorescence quenching. Very similar CO₂-concentration dependencies are found in the absence and presence of methylviologen, which is known to catalyze O₂-reduction, and in the presence of glyceraldehyde, which blocks Calvin cycle and photorespiration. It is suggested that the CO₂-enhanced uptake signal is likely to reflect O₂-uptake in the Mehler reaction. However, it is not ruled out that also rapid CO₂-solubilisation or CO₂-binding caused by light-induced stroma alkalisation are involved. Strong uptake is also induced when the CO₂-concentration in the closed photoacoustic chamber increases due to dark-respiration. The consequences of these findings with respect to the interpretation of photoacoustic data (e.g., low-light effect) and to the regulatory role of O₂-dependent electron flow are discussed.     

A preliminary study of vocal communication in wild long-tailed macaques (Macaca fascicularis). II. Potential of calls to regulate intragroup spacing

This study is a preliminary assessment of the potential of long-tailed macaque (Macaca fascicularis) calls to operate in systems of within-group spacing. Covariation in the rate of occurrence of calls with party spread, size, and activity among wild individuals of one group suggested that four classes of calls may function in intragroup spacing. Two of them are “clear” calls of long duration and pronounced frequency modulation. Calling rate increased with party spread for low- and high-frequency variants of these calls during resting and feeding respectively, suggesting possible utility in maintenance of spatial relations over moderately long distances. A third “harsh” call was negatively correlated with party spread during foraging and may thus function to increase dispersion among foraging individuals. Another harsh call with a tonal onset was unique among all calls in the vocal repertoire in being more frequently performed by lone, isolated individuals than by macaques accompanied by others, suggesting a possible function in reestablishing contact that has been severed. The functional significance of these calls with respect to their acoustic structures is discussed. Macaques that use calls to regulate intragroup spacing can control communication distance and direction by their choice of acoustically different vocalizations. This choice may be affected not only by varying environmental constraints on sound transmission, but also by social and ecological factors such as intragroup competition.     

Early gene interaction during prepupal expression of Drosophila arginine kinase

Arginine kinase displays a distinctive rise and fall in specific activity and specific protein levels during the prepupal stage of Drosophila development with maximal activity occurring at morphological stage P3. This developmentally regulated peak is under the influence of ecdysone. Altered doses of the major ecdysone-inducible “early” genes at cytological regions 75B and 2B5 alter this pattern of expression while altered doses of another major “early” gene at 74EF have no effect. We hypothesize that a product of the 2B5 locus and a product of the 75B locus interact to effect this developmental pattern of expression of Drosophila arginine kinase. © 1992 Wiley-Liss, Inc.     

Comparative properties of ferredoxins from a marine and freshwater species of Porphyridium

Ferredoxins were isolated from the freshwater red alga Porphyridium aerugineut, and from Porphyridium cruentum, a related marine species. A sin