Gibberellic acid-insensitive semi-dwarfs of Triticum dicoccum have delayed aleurone function

Aleurone tissue is known for its function of secreting a number of hydrolytic enzymes including α-amylases, nucleases and proteases in response to gibberellic acid (GA). The effect of GA on aleurone tissue function was studied in Triticum dicoccum including a tall variety, its semi-dwarf mutant and a semi-dwarf variety carrying RhtB1b allele, using isolated aleurone layers. A comparison of the tall and semi-dwarfs revealed that there was a decrease in the amount of α-amylase secreted and also a delay in its stimulation in the two semi-dwarfs. α-Amylase secretion exhibited a peak when the amount of α-amylase activity secreted was plotted as a function of time interval. The semi-dwarfs showed a delay in the appearance of the peak indicating that there was a delay in their response to GA treatment. Presence of GA also caused increased aleurone mitochondrial activity and enhanced loss of nitrogen and dry weight. Delays were also observed in time required to attain the peaks of the mitochondrial activity of the aleurone layer, total protein secreted in the medium, total loss in nitrogen and dry weight from the aleurone layer. The pattern of aleurone function was similar in both the semi-dwarfs, however, there was a greater delay in aleurone function in the new mutant as compared to the RhtB1b semi-dwarf. The altered GA signaling due to mutation(s) in the two GA insensitive semi-dwarfs may have resulted in a delay in attaining peak activity of the aleurone layers.