Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

PHOSPHORYLATION DURING MALE MEIOSIS AND RELATIONSHIP WITH MICROTUBULE CYTOSKELETON

CREMONA G.*, CAPO A.*, ERRICO A.*, CONICELLA C.**

* Department of Agronomy and Plant Genetics, University of Naples,Via Università 100, 80055 Portici, Italy

** CNR-IMOF, Research Institute for Vegetable and Ornamental Plant Breeding, Via Università 133, 80055 Portici, Italy

conicell@unina.it

cytoskeleton, kinases, immunolocalization, meiosis, reproduction

Components of the plant cytoskeleton were previously investigated in meiotic mutants with ploidy variation in the gametes. The main abnormalities were displayed by the organization of the microtubular cytoskeleton during the cytokinesis in nuclear-based radial microtubule system and phragmoplast/cell plate formation. It was formulated the hypothesis that the nucleation of microtubules could be repressed or slowed down in the mutants. Among the elements interacting with microtubules and influencing their dynamics, the attention was focussed on the putative role of kinases. Their role was demonstrated in plant mitosis: they act by phosphorylation of cell cycle key components or, indirectly, by phosphorylation of other kinases by cascade events.

In the present work, the phosphorylation activity was investigated in male meiocytes using a monoclonal antibody (MPM-2) which recognizes a phosphoprotein class of 55-210 kDa. These proteins are aboundant in mitogen cells and are cell cycle-regulated. The MPM-2-reactive proteins are characterized by a phosphoepitope which contains phosphothreonine and they are reported to be associated with cytoskeletal elements. In this work, the double immunolocalization in meiocytes was set up with MPM-2 and anti-a-tubulin antibodies in a wild-type strain. Phosphorylation dinamically marked all meiotic stages, showing a similar pattern of distribution in both meiosis I and II. The labelling occurred within the nucleus in prophase I and II, and it seems to be concentrated between chromosomes. At metaphase and anaphase I and II, immunofluorescence disappeared in the nucleus and it became localized on the spindles. During telophase II, the labelling was strong in the nuclei at the beginning and then, it marked the radial microtubule system. The experiments of double immunolocalization are in progress in the meiotic mutants.

In conclusion, phosphorylation and dephosphorylation of MPM-2 epitopes were described to occur during plant meiosis for the first time and they could be one of the mechanisms by which microtubule rearrangements are regulated.