Megasporogenesis in Arabidopsis thaliana L.: an ultrastructural study |
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Authors: | C Bajon C Horlow J C Motamayor A Sauvanet D Robert |
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Institution: | (1) Université Pierre et Marie Curie, Laboratoire de Biologie de la Reproduction des végétaux, BP 32, 75252 Paris, Cedex 05, France, FR;(2) INRA Versailles, Station de Génétique et d’Amélioration des Plantes, Route de St Cyr, 78026 Versailles Cedex, France, FR;(3) Laboratoire AGETROP/CIRAD, BP 5035, 34032 Montpellier Cedex 01, France, FR |
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Abstract: | In this study, megasporogenesis of the plant model Arabidopsis thaliana was investigated by electron microscopy for the first time. The data described here could constitute a reference for future
investigations of Arabidopsis mutants. During the beginning of meiosis the megaspore mother cell shows a polarity created by unequal distribution of organelles
in the cytoplasm. Plastids accumulate in the chalazal region and long parallel saccules of endoplasmic reticulum, small vacuoles
and some dictyosomes are found in the micropylar region. Plasmodesmata are abundant in the chalazal cell wall. The nucleus
is almost centrally localized and contains a prominent excentric nucleolus and numerous typical synaptonemal complexes. After
the second division of meiosis the four megaspores are separated by thin cell walls crossed by numerous plasmodesmata and
do not show significant cellular organization. The young functional megaspore is characterized by a large nucleus and a large
granular nucleolus. The cytoplasm is very electron dense due to the abundance of free ribosomes and contains the following
randomly distributed organelles: mitochondria, a few short saccules of endoplasmic reticulum, dictyosomes and undifferentiated
plastids. However, there is no apparent polarity, except for the distribution of some small vacuoles which are more abundant
in the micropylar region of the cell. The degenerating megaspores are extremely electron dense and do not show any substructure.
Received: 30 July 1998 / Revision accepted: 3 February 1999 |
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Keywords: | Arabidopsis thaliana Megasporogenesis Meiosis Ultrastructure Cellular polarity |
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