Molecular and physiological markers during seed development of peppers (Capsicum annuum L.): DNA replication and beta-tubulin synthesis

The correlation between physiological markers for seed maturity (acquisitio n of germinability, definitive morphological traits and desiccation toleran ce) and timing of the shutdown of nuclear replication activity and beta-tub ulin synthesis has been investigated in developing pepper seeds. Nuclear re plication activity was analysed by flow cytometry. Expression of beta-tubul in, a cell-cycle related structural protein, was detected in western blots of total protein extracts. In pepper embryos, DNA synthesis stopped 42-49 d ays after anthesis (DAA), at which time seeds started to acquire desiccatio n tolerance. A clear beta-tubulin signal was detected up to 63 DAA, only 1 week before the acquisition of complete desiccation tolerance. Both nuclear replication and beta-tubulin synthesis can therefore be used as markers fo r the physiological stage reached by developing pepper seeds. Detection of beta-tubulin signals in embryonic tissues can also be helpful in discrimina ting immature seeds within a commercial seed lot.