Hormonally regulated programmed cell death in barley aleurone cells

Cell death was studied in barley (cv Himalaya) aleurone cells treated with abscisic acid and gibberellin. Aleurone protoplasts incubated in abscisic a cid remained viable in culture for at least 3 weeks, but exposure to gibber ellin initiated a series of events that resulted in death, Between 4 and 8 days after incubation in gibberellin, >70% of all protoplasts died. Death, which occurred after cells became highly vacuolated, was manifest by an abr upt loss of plasma membrane integrity followed by rapid shrinkage of the ce ll corpse. Hydrolysis of DNA began before death and occurred as protoplasts ceased production of alpha-amylase. DNA degradation did not result in the accumulation of discrete low molecular weight fragments. DNA degradation an d cell death were prevented by LY83583, an inhibitor of gibberellin signali ng in barley aleurone. We conclude that cell death in aleurone cells is hor monally regulated and is the final step of a developmental program that pro motes successful seedling establishment.