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#beta#-tubulin synthesis and DNA replication in imbibing seeds of tomato (Lycopersicon esculentum Mill.)

Zheng Xiaoying, Bino R J, Bergervoet HW

Beijing Vegetable Research Center. Beijing 100081； The Netherlands

Abstract

The activation of the cell cycle in embryo root tips of imbibing tomato seeds was studied by immunodetection of #beta#-tubulin, a major component of microtubules, and by flow cytometric analysis of nuclear DNA contents. In dry seeds, #beta#-tubulin was not detectable on Western blots and flow cytometric profiles indicated that the majority of the cells were arrested at phase G1 of the cell cycle. Upon imbibition in water, a clear 55 kD #beta#-tubulin signal was detected within 8 to 16 h while the number of cells in G2 increased after 24 h, suggesting that tubulin synthesis preceded DNA replication. The signal of #beta#-tubulin was stronger at 48 h of imbibition and disappeared once the root tip had protruded through the seed coat. Two-dimensional immunoblots revealed at least three different #beta#-tubulin isotypes. Both #beta#-tubulin synthesis and DNA replication were also induced by priming in PEG. These processes, as well as the seed germination rate, were enhanced upon subsequent imbibition in water, compared with untreated seeds. By contrast, upon imbibition of aged seeds #beta#-tubulin synthesis, DNA replication and germination were delayed. In all seeds, both #beta#-tubulin synthesis and DNA replication preceded visible germination. It is suggested that the activation of these cell cycle-related processes is a prerequisite for tomato seed germination.

Key words: Tomato seed;#beta#-tubulin;DNA replication;Cell cycle;Immunodetection

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Citing This Article：

Zheng Xiaoying, Bino R J, Bergervoet HW. #beta#-tubulin synthesis and DNA replication in imbibing seeds of tomato (Lycopersicon esculentum Mill.). Acta Physiol Sin 1996; 48 (4): (in Chinese with English abstract).