Zygospore formation in different strains of the Closterium peracerosum-strigosum-littorale complex was examined in this unicellular isogamous charophycean alga to shed light on gametic mating strains in this taxon, which is believed to share a close phylogenetic relationship with land plants. Zygospores typically form as a result of conjugation between mating-type plus (mt(+)) and mating-type minus (mt(-)) cells during sexual reproduction in the heterothallic strain, similar to Chlamydomonas. However, within clonal cells, zygospores are formed within homothallic strains, and the majority of these zygospores originate as a result of conjugation of two recently divided sister gametangial cells derived from one vegetative cell. In this study, we analyzed conjugation of homothallic cells in the presence of phylogenetically closely related heterothallic cells to characterize the reproductive function of homothallic sister gametangial cells. The relative ratio of non-sister zygospores to sister zygospores increased in the presence of heterothallic mt(+) cells, compared with that in the homothallic strain alone and in a coculture with mt(-) cells. Heterothallic cells were surface labeled with calcofluor white, permitting fusions with homothallic cells to be identified and confirming the formation of hybrid zygospores between the homothallic cells and heterothallic mt(+) cells. These results show that at least some of the homothallic gametangial cells possess heterothallic mt(-)-like characters. This finding supports speculation that division of one vegetative cell into two sister gametangial cells is a segregative process capable of producing complementary mating types.
The vaginal mucosa is the most common site of initiation of virus infections that are transmitted through heterosexual intercourse, including HIV and papillomavirus. Thus, in order to prevent or treat these infections, strong vaginal immunity is required as the first line of defense. In this study, to establish a less invasive, safe, convenient and effective immunization method, we examined the local (skin and vagina) gene transfection efficiency of a non-needle jet injector for daily insulin injection. In the skin experiment, the needle-free injector resulted in a marked increase in marker gene expression, compared to the conventional needle-syringe injection. In addition, intradermal DNA vaccination using the needle-free injector dramatically induced IFN-gamma and antibody systemic responses in mice. Furthermore, we investigated the applicability of the needle-free injector as a vaginal vaccination tool in rabbits. Vaginal gene expression using the needle-free injector was significantly greater than that using needle-syringe injection. Moreover, intravaginal vaccination by the needle-free injector promoted vaginal IgA secretion and IFN-gamma mRNA expression in the blood lymphocytes, to a degree significantly higher than that by needle-syringe injection. In conclusion, local vaginal DNA vaccination using a needle-free jet injector is a promising approach for the prevention and treatment of mucosal infectious diseases.
To investigate the local vaginal and systemic immune responses of effective vaginal DNA delivery with high transfection efficiency, we determined the effects on Th1-dependent cytokine (interferon-gamma) production in spleen and inguinal lymph node cells and antibody responses of vaginal pDNA immunization with a cell-penetrating peptide, and compared our vaginal immunization with intradermal and intranasal immunizations.
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