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Information on population genetics is fundamental to developing in situ or ex situ conservation strategies. Few researchers, however, have compared the genetic structure of restored and natural populations of threatened plant species. Metasequoia glyptostroboides Hu & Cheng (dawn redwood) (Taxodiaceae), a living fossil endemic to China, may be the most successfully recovered threatened species, with many more individuals and a much wider distribution than fossil records indicate. We used random amplification of polymorphic DNA markers to compare the genetic structure of artificial populations with that of wild ones and to determine whether the genetic structure of M. glyptostroboides has been recovered as has its distribution. The genetic variation of wild populations of M. glyptostroboides was lower than the average of gymnosperms, indicating the effects of glaciations and recent habitat loss and fragmentation. Genetic variation in artificial populations was less, but not substantially, compared with wild populations. The unweighted pair group method with arithmetic mean revealed that the wild and the artificial populations formed two distinct groups. Artificial populations were more similar to each other (mean Nei's genetic distance = 0.0924) than to wild populations (mean distance = 0.2054). This might be the result of biased seed collection, vegetative propagation, or a mixture of propagules from different populations and an ultimate propagule source. These results suggest that although the quantity and distribution range have been successfully restored, the genetic structure of M. glyptostroboides has not recovered appropriately, given the loss of genetic variation and biased genetic composition in artificial populations. Therefore, in addition to protecting the wild populations, additional ex situ genetic reserves should be established based on genetic knowledge and via appropriate approaches. We suggest that population genetic and demographic indices should be considered when downlisting or delisting threatened species.Resumen: Es fundamental contar con información sobre genética poblacional para el desarrollo de estrategias de conservación in situ o ex situ. Sin embargo, pocos investigadores han comparado la estructura genética de poblaciones restauradas y naturales de especies de plantas amenazadas. Metasequoia glyptostroboides Hu & Cheng (Taxodiaceae), un fósil viviente endémico de China, puede ser la especie amenazada recuperada más exitosamente, con mucho más individuos y una distribución mucho mayor que la indicada por registros fósiles. Utilizamos amplificaciones aleatorias de marcadores de ADN polimórfico para comparar la estructura genética de poblaciones artificiales con la de poblaciones silvestres y para determinar si la estructura genética de M. glyptostroboides se ha recuperado como lo ha hecho su distribución. La variación genética de ‡Address correspondence to X.-Y. Chen, email Li et al. Genetic Variation in Metasequoia 225poblaciones silvestres de M. glyptostroboides fue menor que la del ...

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Background information. The DM (doublesex and male aberrant-3) genes implicated in sexual development in diverse metazoan organisms have been proved to be involved in development of non-gonadal tissues. The aim of the present study was to identify and characterize Dmrt3 (DM-related transcription factor 3) of zebrafish.Results. Zebrafish Dmrt3 has a conserved DMA domain, besides a common DM domain, which clustered it into the DMRTA subfamily. During embryogenesis, Dmrt3 expression increases gradually to a high level at pharyngula stage, which is restricted to the olfactory placode and the neural tube. In the juvenile zebrafish, the gene expression is first detected in undifferentiated gonad on 17 dpf (day post-fertilization). In adult, Dmrt3 is expressed only in the developing germ cells of both gonads, mainly in spermatogonia, spermatocytes and developing oocytes. The Dmrt3 has a functional NLS (nuclear localization signal) K 41 GHKR 45 within the DM domain, which ensures that Dmrt3 exerts its role in the nucleus. Moreover, EMSA (electrophoretic mobility-shift assay) indicates that the Dmrt3-derived DM polypeptide binds to similar sites of both targets of DSX (doublesex) and MAB-3 (male aberrant-3).Conclusion. These results suggest that as a DNA-binding protein, zebrafish Dmrt3 may function in the nucleus as a potential transcription factor to exert potential roles in the development of the olfactory placode, the neural tube and germ cells.

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