Type of presentation: Poster

LS-2-P-3510 Lacandonia granules are present in Welwitschia mirabilis

Agredano-Moreno L. T.1, Segura-Valdez M. L.1, Muñiz Díaz de León M. E.2, Jiménez-Ramírez J.2, Jiménez-García L. F.1
1Departamento de Biología Celular, Facultad de Ciencias, UNAM, , 2Departamento de Biología Comparada, Facultad de Ciencias, UNAM.
agredano-moreno@ciencias.unam.mx

Lacandonia granules are extranucleolar ribonucleoprotein (RNPs) particles, 32 nanometers in diameter intermixed with fibrils that were first described in the nucleoplasm of the plant Lacandonia schismatica (Jiménez-García, et al. 1992). Cytochemical and imunocytochemical 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 (Agredano-Moreno & Jiménez-García, 2000). In addition, Lacandonia granules have been reported in other close groups as Triuris brevystilis (Jiménez-García, et al. 1992), and even in the tree Ginkgo biloba (Jiménez-Ramírez et al. 2002). In the present work we analyzed the presence of Lacandonia granules in Welwitschia mirabilis. Samples of plant leaves grown in greenhouse were processed for electron microscopy. Light, electron and atomic force microscopy revealed that nuclei are reticulated according to compact chromatin distribution. Granules of 32 nm in diameter, positive to the EDTA regressive technique for RNP, distributed in the perichromatin and interchromatin space were observed among strands of reticulated chromatin (Figure 1). Stereo pair images from ultrathin sections showed fibers and granules intermingled. Our results show that Lacandonia granules are also present in the order Gnetales, associated to reticulated chromatin.

References
Jiménez-García, L.F., Agredano-Moreno, L.T., Segura-Valdez, M. de L. Echeverría, O., Martínez, E., Ramos, C.H., Vázquez-Nin, G.H. 1992. The ultrastructural study of the interphase cell nucleus of Lacandonia schismatica (Lacandoniaceae:Triuridales) reveals a non-typical extranucleolar particle. Biol. Cell. 75:101-110

Agredano-Moreno, L.T., Jiménez-García, L.F. 2000. New evidence that Lacandonia granules are ultrastructurally related to perichromatin and Balbiani ring granules. Biol. Cell. 92:71-78

Jiménez-Ramírez, J., Agredano-Moreno, L.T., Segura-Valdez, M de L., Jiménez-García, L.F. 2002. Lacandonia granules are present in Ginkgo biloba cell nuclei. Biol. Cell. 94:511-518

DGAPA-PAPIME PE211412

Fig. 1: Electron micrograph showing Lacandonia granules (arrows) in the cell nucleus of meristematic cell of Welwitschia mirabilis. EDTA regressive staining for RNP. Chromatin (C). Bar is 80 nm.