Assessment of Behavioural Parameters of Chironomus Tentans and Lumbriculus Variegatus for the use in a New Early Warning Biomonitoring System for Drinking Water

Assessment of Behavioural Parameters of Chironomus Tentans and Lumbriculus Variegatus for the use in a New Early Warning Biomonitoring System for Drinking Water

Assessment of Behavioural Parameters of Chironomus Tentans and Lumbriculus Variegatus for the use in a New Early Warning Biomonitoring System for Drinking Water

Assessment of Behavioural Parameters of Chironomus Tentans and Lumbriculus Variegatus for the use in a New Early Warning Biomonitoring System for Drinking Water

Lacandonia granules are present in the cell nucleus of Welwitschia mirabilis

<p><strong>Background:</strong> <em>Lacandonia</em> granules are extranucleolar ribonucleoprotein (RNPs) particles, 32 nanometers in diameter that were first described in the nucleus of <em>Lacandonia schismatica</em>. Cytochemical and immunocytochemical studies suggest that these particles are equivalent to perichromatin and Balbiani ring granules described in mammals and salivary glands cells of the insect <em>Chironomus tentans, </em>respectively. <em>Lacandonia</em> granules are also present in the related <em>Triuris</em> <em>brevystilis</em>,<em> </em>and they were later described in the gymnosperm <em>Ginkgo biloba</em>. These findings suggest that <em>Lacandonia </em>granules have a wider distribution in the plant kingdom. </p><p><strong>Species study:</strong> The plant <em>Welwitschia mirabilis, </em>a gymnosperm of the order Gnetales.</p><p><strong>Hyphotesis: </strong><em>Lacandonia</em> granules are present in the cell nucleus of <em>W. mirabilis</em>.<strong> </strong></p><p><strong>Methods:</strong> Plants were cultivated<strong> </strong>in a germination chamber and samples of leaves were processed for transmission electron microscopy. Thin sections were stained with the EDTA technique preferential for ribonucleoproteins and osmium amine specific for DNA and observed with a microscopy.</p><p><strong>Results:</strong> Light, electronic and atomic force microscopy revealed that cell nuclei of <em>W. mirabilis</em> display a reticulated arrangement of chromatin. Moreover, granules of 32.17 ± 1.7 nm in diameter were observed among strands of reticulated chromatin.</p><p><strong>Conclusions:</strong> Our results indicate that <em>Lacandonia</em> granules are present in the nuclei of the gnetal <em>W. </em> <em>mirabilis.</em></p>

Transcription regulation during stable elongation by a reversible halt of RNA polymerase II

Regulation of RNA polymerase II (RNAPII) during transcription is essential for controlling gene expression. Here we report that the transcriptional activity of RNAPII at the Balbiani ring 2.1 gene could be halted during stable elongation in salivary gland cells of Chironomus tentans larvae for extended time periods in a regulated manner. The transcription halt was triggered by heat shock and affected all RNAPII independently of their position in the gene. During the halt, incomplete transcripts and RNAPII remained at the transcription site, the phosphorylation state of RNAPII was unaltered, and the transcription bubbles remained open. The transcription of halted transcripts was resumed upon relief of the heat shock. The observed mechanism allows cells to interrupt transcription for extended time periods and rapidly reactivate it without the need to reinitiate transcription of the complete gene. Our results suggest a so-far-unknown level of transcriptional control in eukaryotic cells.