Glycosylation of phytepsin and expression of dad1, dad2 and ost1 during onset of cell death in germinating barley scutella

Dysfunction and downregulation of dad (defending against death) has been linked to programmed cell death (PCD) in animals and plants. As DAD is an essential subunit of the oligosaccharyltransferase that is located in the ER membrane, the results have raised the possibility that downregulation of N-linked glycosylation could be involved in the regulation of PCD. Here we show that the 16 kDa subunit of phytepsin, a vacuolar proteinase, is normally processed and glycosylated at the onset of DNA fragmentation in germinating barley scutella. Two cDNA clones encoding dad (dad1, dad2), and one cDNA encoding another subunit of the same oligosaccharyltransferase complex (ost1) were isolated from barley. Northern analysis of germinating scutella show that the expression of only dad1 is declining before onset of DNA fragmentation. In contrast to this, the expression of both dad2 and ost1 increase before onset of DNA fragmentation.