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Results for “Gametogenesis”

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PubMed1997

The roles of temperature, pH and mosquito factors as triggers of male and female gametogenesis of Plasmodium berghei in vitro.

Developmentally arrested malarial gametocytes undergo gamete formation in the mosquito midgut immediately after ingestion of the infected bloodmeal. In the rodent malaria parasite Plasmodium berghei male gametogenesis (exflagellation) can be induced in vitro by a temperature decrease (from 39 degrees C in the vertebrate host to 20 degrees C) and a concomitant pH increase (from 7.3 in mouse blood to 8.0). We report the presence of additional Gametocyte Activating Factor(s) (GAF) present in Anopheles stephensi tissue extracts, which induce both male and female gametogenesis at the otherwise nonpermissive pH of 7.3 in vitro but are unable to overcome the low temperature requirement. All constituent cellular events of microgametogeneis studied here are induced by the same triggers in vitro. A temperature decrease is also required for exflagellation in the mosquito midgut. The possible role of GAF as a second obligatory natural trigger of gametogenesis is discussed.

Animals↗

PubMed2004

A classical arabinogalactan protein is essential for the initiation of female gametogenesis in Arabidopsis.

Classical arabinogalactan proteins (AGPs) are an abundant class of cell surface proteoglycans widely distributed in flowering plants. We have used a combination of enhancer detection tagging and RNA interference (RNAi)-induced posttrancriptional silencing to demonstrate that AGP18, a gene encoding a classical arabinogalactan protein, is essential for female gametogenesis in Arabidopsis thaliana. AGP18 is expressed in cells that spatially and temporally define the sporophytic to gametophytic transition and during early stages of seed development. More than 75% of the T1 transformants resulted in T2 lines showing reduced seed set during at least three consecutive generations but no additional developmental defects. AGP18-silenced T2 lines showed reduced AGP18 transcript levels in female reproductive organs, the presence of 21-bp RNA fragments specific to the AGP18 gene, and the absence of in situ AGP18 mRNA localization in developing ovules. Reciprocal crosses to wild-type plants indicate that the defect is female specific. The genetic and molecular analysis of AGP18-silenced plants containing a single T-DNA RNAi insertion suggests that posttranscriptional silencing of AGP18 is acting both at the sporophytic and gametophytic levels. A cytological analysis of all defective AGP18-RNAi lines, combined with the analysis of molecular markers acting at key stages of female gametogenesis, showed that the functional megaspore fails to enlarge and mitotically divide, indicating that AGP18 is essential to initiate female gametogenesis in Arabidopsis. Our results assign a specific function in plant development to a gene encoding a classical AGP.

Arabidopsis↗

PubMedDate not supplied

[Microspectral studies of neuroendocrine regulation of gametogenesis in mollusks].

An associated culture of nervous ganglia and gonads was used to study the gametogenesis neuroendocrine regulation in mollusks (Mytilus edulis L.). The state of oocytes was controlled by microspectral fluorescent analysis on slides stained with acridine orange. The object of investigations was Mytilus edulis L. collected in La Manch in April-May. A microspectrofluorimetrical investigation of samples was carried out in Pushchino. As a criterion of cell synthetic activity, the parameter alpha was used. Parameter alpha is the ratio of fluorescence intensities in the red (I640) and green (I530) regions of the visible spectrum: alpha = I640/I530. The results obtained showed that the nervous system realized the endocrine regulation of gametogenesis in mollusks. There was no normal development of oocytes in an isolated mantle culture. The development of oocytes in a tissue culture proceeds in a similar manner as in the gonads of the native organism in normal natural conditions only if the mantle tissue is associated either with all nervous ganglia or with the cerebral ganglion alone. It was found that the cerebral ganglion plays a key role in the neuroendocrine regulation of gametogenesis.

Animals↗

PubMed2005

parva germina, A gene involved in germ cell maintenance during male and female Drosophila gametogenesis.

We report the initial characterization of a gene, parva germina (pag), required for germ cell maintenance in both males and females. pag gonads contain a small number of germline stem cells at the onset of gametogenesis. In contrast, adult mutant gonads are either empty or have a very small number of germ cells that never develop in 16-cell cysts. Ovarioles and testes, therefore, are rudimentary, and the very few germ cells they contain are unable to differentiate into eggs or sperm. Germline stem cells are progressively depleted over time. The average number of germ cells, therefore, decreases in pag mutant ovarioles with the age of the mother, whereas the proportion of agametic germaria goes up. These observations suggest that the pag gene product is involved in germ cell maintenance in both male and female gametogenesis.

Animals↗

PubMed2005

Expression of rck/p54, a DEAD-box RNA helicase, in gametogenesis and early embryogenesis of mice.

rck/p54 is a DEAD-box RNA helicase protein with ATP-dependent RNA-unwinding activity. Its ortholog is required for sexual reproduction in yeast and for oocyte survival and sperm fertility in Caenorhabditis elegans. In the current study, we investigated the expression of rck/p54 in mouse gametogenesis and early embryogenesis. Western blot analysis revealed that rck/p54 was highly expressed in both the ovary and testis. In the ovary, maturing oocytes strongly expressed rck/p54 in their cytoplasm. In contrast, in the testis, spermatogonia and primary spermatocytes highly expressed rck/p54 in their cytoplasm, but its expression decreased in the spermatids. Interestingly, rck/p54 was concentrated in the heads of spermatozoa; and then its expression gradually decreased as these cells matured along the epididymal duct. After fertilization, rck/p54 protein and its mRNA remained present in the pronucleus phase; and then their expression levels slightly but definitely decreased in morulae and blastocytes. The injection of a CMV-based rck/p54 expression vector into the pronuclei of fertilized eggs caused a delay in early embryogenesis. In generating RCK transgenic mice, the birth rate of the mice was significantly lower than those of other gene transgenic mice. These findings indicate that rck/p54 may play an important role in gametogenesis and early embryogenesis in mammals.

Animals↗

PubMed2000

Lemon encodes an unusual receptor protein-tyrosine kinase expressed during gametogenesis in Hydra.

In a screen for receptor protein-tyrosine kinase (RTK) genes expressed during gametogenesis in the cnidarian Hydra vulgaris, we isolated a cDNA encoding Lemon, an RTK with unusual features. Lemon is orthologous to Drosophila Dtrk, chicken Klg, and human colon carcinoma kinase-4. These genes constitute an RTK class characterized by a conserved transmembrane sequence, the presence of extracellular immunoglobulin-like repeats, and the absence of the DFG motif in the kinase domain. We provide evidence that Lemon is a component of an unusual RTK signal transduction mechanism that may involve transmembrane domain-mediated interactions and may not be dependent on its own catalytic activity. Lemon transcription is dynamically regulated in interstitial cells during asexual budding and gametogenesis. Transcriptional up-regulation occurs early in spermatogenesis and oogenesis concurrent with the local accumulation of interstitial cells in the body column of sexual polyps.

Amino Acid Sequence↗

PubMed1991

Plasmodium berghei: ionic regulation and the induction of gametogenesis.

The role of ionic regulation in the induction of gametogenesis of Plasmodium berghei at 20 degrees C was investigated. A potent inhibitor of Na+/H+ exchange, amiloride, strongly inhibited exflagellation and subsequent ookinete formation induced by RPMI 1640 with 10% fetal calf serum at pH 8.0, whereas Na+ or K+ channel inhibitors, H(+)-ATPase inhibitors, and a protonophore had no significant effect. Amiloride-treated 'activated' microgametocytes synthesized DNA to levels consistent with the expected 8C, but failed to develop further. These results may suggest that an increase in intracellular pH induced by Na+/H+ exchange plays an important role in the induction of gametogenesis by cultivating at pH 8.0 and 20 degrees C. Cultivation at pH 8.0 and 37 degrees C did not induce the development, and microgametocytes remained as nonactivated forms, having the DNA content of 1.5C. By culturing at pH 7.3 and 20 degrees C, however, most of microgametocytes finished synthesis of DNA up to the 8C level, but ceased development at various stages. Additionally, exflagellation occurred in a simple medium composed of buffered saline with 10 mM glucose. Glucose was indispensable for exflagellation, presumably acting as an energy source. Exflagellation induced by this solution was also inhibited by amiloride. It is therefore suggested that the induction of microgametogenesis may be composed of two distinct mechanisms, one is a temperature-dependent DNA synthesis and the other is a pH-dependent control of developmental events leading to microgamete assembly and exflagellation.

Amiloride↗

PubMed2005

Plasmodium berghei: effect of protease inhibitors during gametogenesis and early zygote development.

Plasmodium berghei: The effect of five protease inhibitors, TPCK, TLCK, PMSF, leupeptin, and 1,10-phenanthroline on in vitro gametogenesis and early zygote development of P. berghei was investigated. PMSF and leupeptin showed no effect. Cysteine/serine protease inhibitors TPCK/TLCK at concentrations of 75 and 100 microM were effective on inhibiting exflagellation center formation, and this effect was reversible with the addition of l-cysteine. Exflagellation center formation was most effectively blocked by 1,10-phenanthroline (1mM), and exflagellation center numbers were restored by the addition of Zn(2+). A reduction of ookinete production was observed when TPCK/TLCK (100 microM) was added at 2h after gametogenesis, but no effect was observed with 1,10-phenanthroline (1mM). Our results suggest that proteolysis is important in both gametocyte activation and sexual development of P. berghei.

Analysis of Variance↗

PubMed2004

The Caenorhabditis elegans eukaryotic initiation factor 5A homologue, IFF-1, is required for germ cell proliferation, gametogenesis and localization of the P-granule component PGL-1.

Eukaryotic initiation factor 5A (eIF-5A) was originally isolated as a translation initiation factor. However, this function has since been reconsidered, with recent studies pointing to roles for eIF-5A in mRNA metabolism and trafficking [Microbiol. Mol. Biol. Rev. 66 (2002) 460; Eur. Mol. Biol. Org. J. 17 (1998) 2914]. The Caenorhabditis elegans genome contains two eIF-5A homologues, iff-1 and iff-2, whose functions in vivo were examined in this study. The iff-2 mutation causes somatic defects that include slow larval growth and disorganized somatic gonadal structures in hermaphrodites. iff-2 males show disorganized tail sensory rays and spicules. On the other hand, iff-1 mRNA is expressed in the gonad, and the lack of iff-1 activity causes sterility with an underproliferated germline resulting from impaired mitotic proliferation in both hermaphrodites and males. In spite of underproliferation, meiotic nuclei are observed, as revealed by presence of immunoreactivity to the anti-HIM-3 antibody; however, no gametogenesis occurs in the iff-1 gonads. These phenotypes are in part similar to the mutants affected in the components of P granules, which are the C. elegans counterparts of germ granules [Curr. Top Dev. Biol. 50 (2000) 155]. We found that localization of the P-granule component PGL-1 to P granules is disrupted in the iff-1 mutant. In summary, the two C. elegans homologues of eIF-5A act in different tissues: IFF-2 is required in the soma, and IFF-1 is required in the germline for germ cell proliferation, for gametogenesis after entry into meiosis, and for proper PGL-1 localization on P granules.

Amino Acid Sequence↗

PubMed2006

Cloning and expression of medaka dazl during embryogenesis and gametogenesis.

The Deleted in azoospermia family consists of RNA-binding proteins Boule, Daz, and Daz-like (Dazl) that are expressed in the germline. Here, we report the cloning and expression of the medakafish (Oryzias latipes) dazl gene (odazl). Interestingly, although the predicted medaka Dazl protein (oDazl) contains a RRM motif and a DAZ repeat characteristic of its mammalian homologs, it lacks 80 aa at the C-terminus. By RT-PCR, RNA in situ hybridization, Western blotting and fluorescent immunohistochemistry using a rabbit anti-Dazl antibody (alphaDazl), we analyzed the expression patterns of odazl and its protein. The odazl transcript persists throughout embryogenesis and delineates with primordial germ cells. In adults, the expression of odazl RNA and its protein is restricted to germ cells of both the testis and ovary. We observed differential expression of RNA and protein at critical stages of gametogenesis. In the testis, the odazl RNA is low at premeiotic stages, abundant at meiotic stages, but absent in postmeiotic stages; whereas the oDazl protein is rich in premeiotic stages, reduced at meiotic stages, becomes barely detectable or absent in postmeiotic round spermatids or sperm, respectively. This is in sharp contrast to the human situation where the Dazl transcript and protein are present in mature spermatozoa. In the ovary, the odazl RNA and protein persist throughout oogenesis and also show differential expression at premeiotic, meiotic and postmeiotic stages. Thus, the odazl or its protein is a marker for germ cells during embryogenesis and at critical stages of gametogenesis in both sexes of medaka.

Amino Acid Sequence↗

PubMed2005

Glycogen synthase kinase 3 has a proapoptotic function in Hydra gametogenesis.

In an approach to study the evolutionary conservation of molecules of the Wnt signal transduction pathway, we analyzed the function of the major negative regulator of this pathway, GSK3 (glycogen synthase kinase 3), in the basal metazoan Hydra. Microinjection assays reveal that HyGSK3 inhibits beta-catenin in zebrafish embryos, indicating that the function of GSK3 in the canonical Wnt signaling pathway is evolutionarily conserved. In Hydra, HyGSK3 transcripts are strongly upregulated during gametogenesis. Treatment of female polyps with the GSK3 inhibitors lithium and alsterpaullone prevents the differentiation of nurse cells and subsequent oocyte formation. Our data indicate that GSK3 is required for the early induction of apoptosis in germline cells, which has been shown to be an initial step in Hydra gametogenesis. Our experiments show that main functions of GSK3 are evolutionarily conserved and unique to multicellular animals, a conclusion which is additionally supported by the presence of specific regulatory domains in the HyGSK3 protein.

Amino Acid Sequence↗

PubMed2001

Both mosquito-derived xanthurenic acid and a host blood-derived factor regulate gametogenesis of Plasmodium in the midgut of the mosquito.

Gametogenesis of Plasmodium in vitro can be induced by the combined stimulus of a 5 degrees C fall in temperature and the presence of xanthurenic acid (XA). In-vitro experiments showed that P. gallinaceum (EC(50)=80 nM) is much more sensitive to XA than P. berghei (9 microM), P. yoelii (8 microM), and P. falciparum (2 microM). However, in the mosquito vector, we do not know whether the temperature shift and XA are the only gametocyte-activating factors (GAF), nor do we know with certainty the true source(s) of XA in the mosquito blood meal. Previous studies indicate that XA is the only source of GAF in the mosquito. By defining, and then contrasting, the ability of an XA-deficient mutant of Aedes aegypti, with the wild-type mosquito to support exflagellation and ookinete formation in vivo, we determined the roles of parasite-, mosquito- and host blood-derived GAF in the regulation of gametogenesis of P. gallinaceum. Removal of both host and vector sources of GAF totally inhibited both exflagellation and ookinete production, whilst the lack of either single source resulted in only a partial reduction of exflagellation and ookinete formation in the mosquito gut. Both sources can be effectively replaced/substituted by synthetic XA. This suggests (1) both mosquito- and vertebrate-derived factors act as GAF in the mosquito gut in vivo; (2) the parasite itself is unable to produce any significant GAF activity. Studies are underway to determine whether vertebrate-derived GAF is XA. These data may form the basis of further studies of the development of new methods of interrupting malarial transmission.

Aedes↗

PubMed2000

Proteolysis of Plasmodium falciparum surface antigen, Pfs230, during gametogenesis.

During Plasmodium falciparum gametogenesis, proteolysis of Pfs230, a 360 kDa gametocyte surface protein, generates two large polypeptides, 307 and 300 kDa, that remain associated with the surface of the newly formed gamete. Using peptide specific antibodies, the amino termini of the 307 and 300 kDa forms have been mapped to between aa 477-487 and aa 523-555, respectively, which is the region between the glutamate rich repeats and the cysteine motif domains. Concomitantly, two peptides, 47 and 35 kDa, corresponding to the region upstream from the cleavage site are released into the medium. The membrane permeant cysteine protease inhibitor, E64d, blocks production of the 300 and 35 kDa forms of Pfs230, but does not alter the formation of the 307 or 47 kDa forms. In contrast, E64, which has been shown to inhibit the development of P. falciparum trophozoites, does not block proteolytic processing of Pfs230. Production of both the 307 and 300 kDa forms was reduced by a metallo-protease inhibitor, 1,10-phenanthroline, whereas the rest of the protease inhibitors tested had no effect on Pfs230 processing. This is the first study of proteolysis during gametogenesis and it demonstrates that the two large forms of Pfs230 produced are generated by proteases with different specificities. The data also suggest that Pfs230 undergoes proteolytic processing prior to emergence from the red blood cell.

Animals↗

PubMed2001

Expression of sGnRH mRNA in gonads during rainbow trout gametogenesis.

The salmon gonadotropin-releasing hormone (sGnRH) is the major form of GnRH decapeptide expressed in the salmonid brain and it acts as a gonadotropin releaser. In rainbow trout, sGnRH-1 and sGnRH-2 mRNA forms were found in brain and gonads. We analyzed the expression of both forms in trout gonads at different stages of gametogenesis. Northern blot demonstrated that sGnRH-2 mRNA was the major sGnRH form in testis and ovary. In testis but not in ovary, brain or pituitary, alternatively spliced sGnRH-2 transcripts which coded for prepro-sGnRH with a truncated GnRH-associated peptide due to a premature stop codon in retained intron 2 were detected. In testis, sGnRH mRNA was highly expressed before the onset of spermatogenesis, it disappeared at stage II and then increased progressively up to stage VI. In ovary, the expression of sGnRH was high in immature pre-vitellogenic fish and progressively decreased throughout vitellogenesis. At ovulation it reached its maximum and came down again after stripping. The decrease of sGnRH mRNA expression during the period of active spermatogonial proliferation in testis and increase during meiosis occurrence in testis and ovary suggest an anti-proliferative and meiosis-stimulating effect of sGnRH during rainbow trout gametogenesis.

Alternative Splicing↗

PubMed2004

Non-traditional roles of ubiquitin-proteasome system in fertilization and gametogenesis.

Fertilization and gametogenesis are key events in sexual reproduction. Our recent studies, together with several reports by other authors, demonstrated that the extracellular ubiquitin-proteasome system plays a role in fertilization and gametogenesis in addition to the traditional intracellular ubiquitin-proteasome system. Here, we summarize our recent results showing the importance of the extracellular ubiquitin-proteasome system in the sperm penetration through the vitelline coat of the egg during ascidian fertilization, together with our recent reports implicating the participation of a novel proteasome-associating complex PC530 in starfish oocyte maturation. We also describe the results by other authors showing the participation of the ubiquitin system both in the elimination of defective sperm in epididymis and in the elimination of paternal mitochondria in fertilized eggs. These are evidence of non-traditional extracellular functions of the ubiquitin system.

Acrosin↗

PubMed2002

Delayed gametogenesis of Mya arenaria in the Saguenay fjord (Canada): a consequence of endocrine disruptors?

The Saguenay fjord located in Canada on the north coast of the Saint-Lawrence Estuary, is well known for its multiple contaminations following a linear distribution upstream to downstream. Mya arenaria is well established in the fjord and potentially exposed to persistent sediment contamination as an endobenthic bivalve. From May to October 1997, clams energy storage and utilization in the gonad was shown to be closely linked with reproduction. Wherever the sampling site location in the fjord, a seasonal pattern is evident for lipid and glycogen levels in the gonad, this, reflecting the vitellogenic process. Nevertheless, in comparison with energy status and gametogenesis of clams collected on the north coast of the Saint-Lawrence Estuary, clams located in the fjord have to face limited nutritive conditions resulting in a single and shorter reproductive period. Although environmental factors could explain differences in physiological condition and reproductive status observed between clams from the fjord and the estuary, our results can discriminate clams from the upper part of the fjord, according to a delayed gametogenesis, concomitant with significant higher gonad glycogen concentrations observed in June 1996 and 1997. A persistent dysfunction of a vitellogenic process is suspected to be due to the exposure to anti-estrogenic contaminants.

Animals↗

PubMed2005

CHR11, a chromatin-remodeling factor essential for nuclear proliferation during female gametogenesis in Arabidopsis thaliana.

Chromatin-remodeling factors regulate the establishment of transcriptional programs during plant development. Although 42 genes encoding members of the SWI2/SNF2 family have been identified in Arabidopsis thaliana, <10 have been assigned a precise function on the basis of a mutant phenotype, and none have been shown to play a specific role during the gametophytic phase of the plant life cycle. A. thaliana chromatin-remodeling protein 11 (CHR11) encodes an imitation of switch (ISWI)-like chromatin-remodeling protein abundantly expressed during female gametogenesis and embryogenesis in Arabidopsis. To determine the function of CHR11 in wild-type plants, we introduced a hairpin construct leading to the production of double-stranded RNA, which specifically degraded the endogenous CHR11 mRNA by RNA interference (RNAi). Transcription of the RNAi-inducing hairpin RNA was driven by either a constitutive cauliflower mosaic virus 35S promoter (CaMV35S) acting at most stages of the sporophytic phase or a newly identified specific promoter acting at the onset of the female gametophytic phase (pFM1). All adult transformants that constitutively lacked sporophytic CHR11 activity showed reduced plant height and small cotyledonary embryos with limited cell expansion. In contrast, RNAi lines in which CHR11 was specifically silenced at the onset of female gametogenesis (megagametogenesis) had normal height and embryo size but had defective female gametophytes arrested before the completion of the mitotic haploid nuclear divisions. These results show that CHR11 is essential for haploid nuclear proliferation during megagametogenesis and cell expansion during the sporophytic phase, demonstrating the functional versatility of SWI2/SNF2 chromatin-remodeling factors during both generations of the plant life cycle.

Adenosine Triphosphatases↗

PubMed1998

Xanthurenic acid induces gametogenesis in Plasmodium, the malaria parasite.

A small, heat stable chromophore extracted from mosquitoes has recently been implicated as the signal that induces mating of Plasmodium, the malaria parasite. We have used high resolution electrospray mass spectrometry to determine that this gamete activation factor (GAF) has a m/z = 205.0450, suggesting a molecular species composition of C10H7NO4. Xanthurenic acid (XA), a product of tryptophan catabolism, was determined to have an elemental composition, ultraviolet absorbance maxima, and mass spectrum consistent with those characteristics of GAF. XA activated gametogenesis of Plasmodium gallinaceum and P. falciparum in vitro at concentrations lower than 0.5 microM in saline buffered to pH 7.4. A structural analog of XA, kynurenic acid (C10H6NO3), also activated gametogenesis but only at higher concentrations and with less effect. We propose that XA is GAF. This is the first evidence that XA has induction activity.

Animals↗