Efficient and stable regeneration from protoplasts of <Emphasis Type="Italic">Cyclamen coum</Emphasis> Miller via somatic embryogenesis

Embryogenic cultures of Cyclamen coum were established on solid media and in suspension, and their growth characteristics in response to different concentrations of plant growth regulators (PGRs) were evaluated. Embryogenic cultures exhibited a high regeneration capacity of 876 somatic embryos per gram fresh mass. Up to 4.24 × 10⁵ protoplasts per gram of fresh mass were isolated from somatic embryos and embryogenic suspension cultures. Protoplasts derived from both embryos and suspension cultures were successfully cultured in vitro and regenerated into plants via somatic embryogenesis. Phenotypic analyses and flow cytometric measurements revealed that some regenerated plants were tetraploid. About 20% of the protoplast-derived calluses used for regeneration were tetraploid, while tetraploidy was found in 0.9% of the plants regenerated from the embryogenic cultures.     

Interspecific resources: a major tool for quantitative trait locus cloning and speciation research

Positional cloning of the quantitative trait locus (QTL) still encounters numerous difficulties, which explains why thousands of QTL have been mapped, while only a few have been identified at the molecular level. Here, we focus on a specific mapping tool that exists in plant and animal model species: interspecific recombinant congenic strains (IRCSs) or interspecific nearly isogenic lines (NILs). Such panels exhibit a much higher sequence diversity than intraspecific sets, thus enhancing the contrasts between phenotypes. In animals, it allows statistical significance to be reached even when using a limited number of individuals. Therefore, we argue that interspecific resources may constitute a major genetic tool for positional cloning and for understanding some bases of speciation mechanisms.     

Classical and molecular genetic analyses of his-3 mutants of Neurospora crassa. II. Southern blot analyses and molecular mechanisms of mutagenicity

Previous studies (Overton et al., Mutation Res., 1989) on specific revertibility of 81 his-3 mutants have shown a correlation between complementation pattern and presumed genetic alteration similar to that shown by ad-3B mutants. In the present study, restriction enzyme analyses were used to further characterize the genetic alterations in individual his-3 mutants. The restriction fragment banding patterns of the majority of mutants were identical with that shown by wild-type 74-OR23-1A and were consistent with expectations based on previous data suggesting that they resulted from single base-pair alterations (Overton et al., Mutation Res., 1989). His-3 mutants with altered banding patterns were only found among those with polarized complementation patterns or noncomplementing mutants. One of the mutants with a polarized complementation pattern, 1-189-83, and another noncomplementing mutant, 1-189-85, are associated with genetic alterations proximal to the his-3 locus. In one other mutant, 1-226-565 (with a polarized complementation pattern), an insertion of approx. 2 kb has occurred in the proximal region of the his-3 locus. Two other mutants, 1-155-270 and 1-155-276 (both noncomplementing), contained a large insertion of approx. 12.8 kb in the proximal region of the his-3 locus.     

Abnormal distribution of the periaxonemal structures in a human sperm flagellar dyskinesia

The spermatozoa from four infertile patients showing a flagellar dyskinesia due to abnormal flagellar wave development have been studied by light and transmission electron microscopy (TEM) for flagellar morphology. No axonemal anomalies were found but modification of the periaxonemal structures was observed. The results of a stereological analysis revealed abnormal extension of the individual dense fibres along the axoneme in the four cases as compared with a control group. The order of termination of those structures was therefore altered. However, the overall fibre extension was the same in both groups (ie, 60% of the principal piece). The number and the location of the longitudinal columns were also modified, the predominant anomaly being the presence of a single column. The possible influence of those structural anomalies on the pattern of sperm movement is discussed. Our observations seem to agree with a previous hypothesis of the literature, that the dense fibres might play a role in flagellar flexibility. More particularly, we suggest that the abnormal extension of dense fibres No. 2, 3, and 4 and the symmetric distribution of the dense fibres on both sides of the plane of beating may alter the flagellar curvature amplitude and the cell rotation frequency.