The sensitivity of barley aleurone tissue to GA is heterogeneous and may be spatially determined.
Sian Ritchie, Andrew McCubbin1, Genevieve Ambrose, Teh-hui-Kao1 and Simon Gilroy
Biology Department, The Pennsylvania State University, 208 Mueller Laboratory, University Park, Pennsylvania 16802
1Department of Biochemistry and Molecular Biology, The Pennsylvania State University, 403 Althouse Laboratory, University Park, Pennsylvania 16802.
ABSTRACT
In cereals, gibberellin (GA) enhances the synthesis and secretion of the hydrolytic enzymes from aleurone cells. These enzymes then mobilize the endosperm storage reserves that fuel germination. The dose-response curve of aleurone cells to GA extends over a range of concentrations from 0.01 to 10 nM. One hypothesis explaining this observation is that sub-populations of cells have different sensitivities to GA, with each cell having a threshold concentration of GA above which it is switched łon˛. The dose-response curve therefore reflects a gradual recruitment of cells to the pool exhibiting a full GA response. Alternatively, all cells could be gradually increasing their response as GA level is increased. We found that at increasing GA concentrations, increasing numbers of cells show the enhanced amylase secretion and vacuolation characteristic of the GA response. We also observed that the region of aleurone tissue closest to the embryo contains the highest proportion of cells that are activated at the GA concentrations thought to naturally occur in germinating grain. These data indicate that an aleurone layer contains cells of varying sensitivities to GA and that recruitment of these differentially responding pools of cells may explain the broad dose-response to GA.
Back to publications