<em>Lacandonia</em> granules are present in the cell nucleus of <em>Welwitschia mirabilis</em>

Abstract

Background: Lacandonia granules are extranucleolar ribonucleoprotein (RNPs) particles, 32 nanometers in diameter that were first described in the nucleus of Lacandonia schismatica. 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 Chironomus tentans, respectively. Lacandonia granules are also present in the related Triuris brevystilis, and they were later described in the gymnosperm Ginkgo biloba. These findings suggest that Lacandonia granules have a wider distribution in the plant kingdom. Species study: The plant Welwitschia mirabilis, a gymnosperm of the order Gnetales. Hyphotesis: Lacandonia granules are present in the cell nucleus of W. mirabilis. Methods: Plants were cultivated 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. Results: Light, electronic and atomic force microscopy revealed that cell nuclei of W. mirabilis display a reticulated arrangement of chromatin. Moreover, granules of 32.17 ± 1.7 nm in diameter were observed among strands of reticulated chromatin. Conclusions: Our results indicate that Lacandonia granules are present in the nuclei of the gnetal W. mirabilis.

Keywords

• Atomic force microscopy
• gymnosperms
• Lacandonia granules
• plant cell ultrastructure
• Welwitschia