Lignins are aromatic polymers of methoxylated phenylpropanoids connected by both ether and carbon-carbon linkages, and classified into three major groups, guaiacyl lignin in softwoods (gymnosperms), guaiacyl-syringyl lignin in hardwoods (angiosperms) and guaiacyl-syringyl-p-hydroxyphenyl lignin in grasses (gramineae) on their monomeric units. In grass lignins p-coumaric acid (5∼10%) is ester linked mostly at γ-position of the propyl side chain. Biochemical studies of lignification have elucidated that 1) lignins are formed by dehydrogenative polymerization of monolignols catalyzed by peroxidase and laccase, 2) biosynthesis of monolignols is via shikimate-cinnamate pathway, 3) syringyl lignin in hardwoods is formed from the syringyl monolignol, sinapyl alcohol, derived from 5-hydroxyguaiacyl precursors, and that 4) ferulate 5-hydroxylase, coniferyl aldehyde 5-hydroxylase and probably coniferyl alcohol 5-hydroxylase are involved in the biosynthesis of the syringyl monolignol from guaiacyl monolignol precursors in respective hardwoods.
(Communicated by Saburo TAMURA, M. J. A., Oct. 14, 2003)
Two new species of douvilleiceratid ammonite, Douvilleiceras compressum and D. kawashitai, are described from the Lower Cretaceous Yezo Group in the Pombetsu Valley of Hokkaido. D. compressum is unique in its compressed whorl section in the genus. D. kawashitai is fairly similar to D. orbignyi Hyatt in its morphological characters, but the former is distinctly characterized by six rows of tubercles, instead of seven for the latter, on each side of the whorl.
(Communicated by Tatsuro MATSUMOTO, M. J. A., Oct. 14, 2003)
The eubacterium Pseudomonas aeruginosa is an opportunistic pathogen, and at the same, possesses a high ability to resist antibiotics and disinfectants. Using the genomic sequence of its standard strain PAO1, determined by another group, genes coding feast/famine regulatory proteins (FFRPs) have been identified. In general, FFRPs regulate transcription of genes, thereby controlling metabolism, growth and environmental adaptation of bacteria, and thus they are obvious targets when designing drugs in order to irradicate P. aeruginosa. In the light of findings on FFRPs of other bacteria, amino acid residues of FFRPs of P. aeruginosa that are likely to be involved in DNA recognition or interaction with natural ligands have been identified. One of the FFRPs, Pa5977610, has been identified as orthologous to an E. coli FFRP, the leucine-responsive regulatory protein (Lrp). Another FFRP, Pa2220251, resembles another E. coli FFRP, YbaO, to a lesser extent. No FFRP of P. aeruginosa is orthologous to the third E. coli FFRP, AsnC. These differences among P. aeruginosa FFRPs can be used for selecting appropriate target proteins, thereby minimizing potential interaction of drugs to be developed with the human symbiont E. coli.
(Communicated by Masanori OTSUKA, M. J. A., Oct. 14, 2003)
One immediate cellular response to DNA damage is the polyADP-ribosylation reaction by poly(ADP-ribose) polymerase-1 (Parp-1). The importance of Parp-1 has been established in many cellular processes, such as the maintenance of genomic stability, DNA repair and cell-death induction. Here, we established Parp-1-/- mice of C57BL/6J congenic strain and characterized the role of Parp-1 in cell-cycle progression. In this study, we also improved a method to observe G0/G1 to S-phase transition of splenocytes and bone marrow cells prepared from mice. The cells were cultured and stimulated with mitogens (50 μM ionomycin/1 μM phorbol 12, 13-dibutyrate). We found that addition of a commercially available growth supportive reagent, BM Condimed RH1, greatly enhanced the transition of G0/G1 to the S-phase, which was determined by bromodeoxyuridine (BrdU) incorporation to DNA. Using this method, G0/G1 to the S-phase entry was measured using splenocytes derived from Parp-1-/-, Parp-1+/- and wild-type (Parp-1+/+) mice. DNA synthesis in Parp-1+/+ and Parp-1+/- splenocytes started from day 1 after addition of mitogens, whereas that in Parp-1-/- cells started from day 2. The peak of the S-phase was at day 2 in all genotypes and notably DNA synthesis in Parp-1-/- cells was approximately halved compared to Parp-1+/+ cells on day 2, 3 and 4. These results suggested that Parp-1 is involved in positive regulation of S-phase entry in quiescent mouse splenocytes.
(Contributed by Takashi SUGIMURA, M. J. A., Oct. 14, 2003)