Analysis of the disassortative mating pattern in a heterodichogamous plant, <Emphasis Type="Italic">Acer mono</Emphasis> Maxim. using microsatellite markers

Heterodichogamy is a form of sex expression in which protandrous and protogynous individuals coexist, and is considered to be a mechanism that avoids selfing and promotes disassortative mating. We examined mating patterns in a heterodichogamous maple, Acer mono, using microsatellite markers. Parentage analysis revealed a selfing rate of only 9.8%. Disassortative mating between flowering types significantly exceeded within-type mating, but the mating patterns were better explained by flowering phenology (i.e., the temporal overlap between the female and male stages). Heterodichogamy in A. mono thus appears to promote outcrossing without requiring obligate self- or cross-incompatibility systems, although it did not guarantee disassortative mating. Multiple-regression analysis suggested that successful reproduction of pollen parents significantly increased with increased flower production and reciprocal flowering synchrony, but decreased only marginally with mating distance, although the distribution of mating distances suggested leptokurtic dispersal of pollen.     

Analysis of the multi-stem clump structure ofLitsea japonica Juss. growing in a coastal dwarf forest

The multi-stem clump structure of a coastal dwarf forest dominated byLitsea japonica Juss. was investigated in order to clarify the sprouting characteristics and self-maintenance of clumps by stem alternation. The size and age distribution of multi-stem clumps were analyzed using cumulative relative frequency curves.L. japonica had a large number of stems and an even height distribution or young age-biased distribution of stems within a clump. These results indicated the sequential flushing of sprouts at high frequency. Height distribution within a clump ofL. japonica was relatively even compared to other species. This clump structure suggested the stable self-maintenance of individuals in all ranges of size and age without disturbances. It originated specific sprouting characteristics as a response to the severe stress of salty wind.Ardisia sieboldii Miq. had few stems within a clump. Although the stem height distribution of large individuals tended to be even, most clumps had a large size-biased distribution of stem height which indicated simultaneous sprouting. From this structure, sprouts of this species were thought to be of less significance in the stable self-maintenance of individuals thanL. Japonica.     

Host-specific plant signal and G-protein activator, mastoparan, trigger differentiation of zoospores of the phytopathogenic oomycete Aphanomyces cochlioides

We found that the gradient of a host-specific attractant, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) isolated from the roots of spinach triggered encystment followed by germination of zoospores of Aphanomyces cochlioidesat a concentration less than micromolar order. This compound did not affect the growth and reproduction of this phytopathogen up to 10^–6 M concentration in the culture medium. We also observed that mastoparan, an activator of heterotrimeric G-protein could inhibit the motility of zoospores and then strikingly effect encystment followed by 60–80% germination of cysts. Concomitant application of cochliophilin A and mastoparan showed stronger encystment followed by 100% germination of cysts. In addition, we have observed that chemicals interfering with phospholipase C activity (neomycin) and Ca²⁺ influx/release (EGTA and loperamide) suppress cochliophilin A or mastoparan induced encystment and germination. These results suggest that G-protein mediated signal transduction mechanism may be involved in the differentiation of the A. cochlioides zoospores. This is the first report on the differentiation of oomycete zoospores initiated by a host-specific plant signal or a G-protein activator.     

Three types of polymorphisms in exon 14 in porcine Mx1 gene

Much is known about the antiviral activity of Mx proteins in species such as mouse and human. In the mouse, loss of resistibility to influenza virus has been shown to be due to specific polymorphisms in the Mx gene. This gene is therefore an interesting candidate gene for disease resistance in farm animals. The porcine Mx1 gene has already been identified and characterized based on its homology with mouse Mx1; however, until now no evidence of polymorphisms in the porcine gene has been reported. In this study, we have found two new polymorphisms in exon 14 of porcine Mx1 by DNA sequencing and confirmed their presence in different breeds, using polymerase chain reaction (PCR)–restriction fragment length polymorphisms (RFLP) with NarI and NaeI restriction enzymes. On the basis of the deduced amino acid sequence, one allele contains a deletion that may result in a frameshift to yield several amino acid substitutions and extension of the carboxyl terminal region of Mx1 protein. The deletion allele, Mx1 ^c, was found to be segregating in Landrace, Berkshire, Duroc, Hampshire, and Yucatan miniature pig. A second point mutation, Mx1 ^b, was detected in Meishan and two Vietnamese native pig breeds. All other breeds tested were fixed for the Mx1 ^a allele that is identical to the sequence reported previously. It will be interesting to determine if the Mx1 ^c deletion is associated with variation in resistance to the myxovirus family in the pig.     

Use of novel selenomethionine-resistant yeast to produce selenomethionyl protein suitable for structural analysis

Yeast is widely used to determine the tertiary structure of eukaryotic proteins, because of its ability to undergo post-translational modifications such as glycosylation. A mutant lacking S -adenosylmethionine synthesis has been reported as a suitable host for producing selenomethionine derivatives, which can help solve phase problems in protein crystallography. However, the mutant required external addition of S -adenosylmethionine for cell proliferation. Here, a selenomethionine-resistant Pichia pastoris mutant that showed S -adenosylmethionine autotrophy was isolated. Human lysozyme expressed by the mutant under the control of constitutive promoter contained selenomethionine at 65% occupancy, sufficient for use as a selenomethionine derivative for single-wavelength anomalous dispersion phasing.     

Utilization and requirements of amino acids by a cell line derived from the butterfly Papilio xuthus

The media, in which a butterfly cell line (Px 58), derived from pharate adult ovaries of Papilio xuthus cultured for 8 days, were analysed to examine the changes in free amino acids in the medium during cultivation. Beta-alanine, arginine, glycine, histidine, lysine, phenylalanine, proline, serine, and tryptophan did not change markedly. Asparagine, aspartic acid, cystine, glutamine, isoleucine, leucine, methionine, threonine, tyrosine, and valine decreased to some extent with culturing. Alpha-alanine increased markedly, and glutamic acid did so to a lesser extent. Requirements of amino acids by the cell line were examined by deleting amino acids one at a time. Deletion of alpha-alanine, beta-alanine, asparagine, glutamic acid, glycine, and phenylalanine did not cause deterioration of the cell. These amino acids were thought to be non-essential or required only a little. Deletion of other amino acids impaired the cell growth severely. These amino acids would appear to be essential for growth of the Px 58 cell line.     

Exposure of conjugative plasmid carrying Escherichia coli biofilms to male-specific bacteriophages

Escherichia coli carrying a natural conjugative F-plasmid generates F-pili mating pairs, which is important for early biofilm formation. In this study, we investigated the effect of male-specific filamentous single stranded DNA bacteriophage (f1) and RNA bacteriophage (MS2) on the formation of biofilms by E. coli carrying a natural conjugative F-plasmid. We showed that the early biofilm formation was completely inhibited by addition of the f1 phage, but not the MS2 phage. This suggests that the tip of F-pili is the specific attachment site for mating pairs formation and the side of F-pili has a non-obligatory role during biofilm formation. The inhibitory effect of the f1 phage was dependent on the time of addition during the biofilm formation. No inhibitory effect was observed when the f1 phages were added to the mature biofilms. This resistant mechanism of the mature biofilms could be attributed to the biofilm-specific phenotypes representing that the F-pili mating pairs were already formed and then the curli production commenced during the biofilm maturation. The pre-formed mating pairs seemed to resist the f1 phages. Altogether, our results indicate a close relationship between the presence of conjugative plasmid and male-specific bacteriophages within sessile biofilm communities, as well as the possibility of using the male-specific bacteriophages to control biofilm formation.