Mitotic Microtubule Development and Histone H3 Phosphorylation in the Holocentric Chromosomes of Rhynchospora Tenuis (Cyperaceae) |
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Authors: | M Guerra A C Brasileiro-Vidal P Arana M J Puertas |
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Institution: | (1) Departamento de Botanica, Centro de Ciências Biológicas, Cidade Universitária, 50.670-420 Recife, PE, Brazil;(2) Departamento de Genética, Facultad de Biología, Universidad Complutense, José Antonio Novais 2, Madrid, 28040, Spain |
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Abstract: | In the present work we report the phosphorylation pattern of histone H3 and the development of microtubular structures using
immunostaining techniques, in mitosis of Rhynchospora tenuis (2n = 4), a Cyperaceae with holocentric chromosomes. The main features of the holocentric chromosomes of R. tenuis coincide with those of other species namely: the absence of primary constriction in prometaphase and metaphase, and the parallel
separation of sister chromatids at anaphase. Additionaly, we observed a highly conserved chromosome positioning at anaphase
and early telophase sister nuclei. Four microtubule arrangements were distinguished during the root tip cell cycle. Interphase
cells showed a cortical microtubule arrangement that progressively forms the characteristic pre-prophase band. At prometaphase
the microtubules were homogeneously distributed around the nuclear envelope. Metaphase cells displayed the spindle arrangement
with kinetochore microtubules attached throughout the entire chromosome extension. At anaphase kinetochoric microtubules become
progressively shorter, whereas bundles of interzonal microtubules became increasingly broader and denser. At late telophase
the microtubules were observed equatorially extended beyond the sister nuclei and reaching the cell wall. Immunolabelling
with an antibody against phosphorylated histone H3 revealed the four chromosomes labelled throughout their entire extension
at metaphase and anaphase. Apparently, the holocentric chromosomes of R. tenuis function as an extended centromeric region both in terms of cohesion and H3 phosphorylation. |
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Keywords: | Cyperaceae H3 phosphorylation holocentric chromosomes kinetochore microtubules Rhynchospora tenuis |
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