Onset of in vitro morphogenic response and protein pattern changes in Phaseolus vulgaris L.

In order to determine the effects of exposure time to benzyl-aminopurine (BAP) and gibberellic acid (GA(3)) on the in vitro organogenic response of Phaseolus vulgaris, shoot-tips and cotyledonary node explants were placed for one to ten days on the MSB6 medium and then transferred to a medium free of phytohormones (MSB). Results show that 50% or more of the explants are induced for shoot regeneration after 4 to 6 days of exposure to the phytohormones on MSB6 and 30 days on MSB. Total soluble proteins from control explants and from explants cultured four days on media with (MSB6) and without (MSB) phytohormones were analyzed by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Differences in the protein pattern between explants on MSB and MSB6 were observed at induction time (the 4th day), namely four polypeptides were associated with the presence of phytohormones in the culture medium. Analyses also revealed changes in protein patterns between uncultured explants and after four days in culture, irrespective of the medium, which were attributed to the stress induced by the in vitro culture. In this case, 12 polypeptides were induced and 17 inhibited in the cultured explants.