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

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