Differential effects of mannitol on gibberellin-regulated phospholipid synthesis and enzyme activities of the CDP-choline pathway in barley aleurone cells
✍ Scribed by D. Koehler; K. D. Johnson; J. E. Varner; H. Kende
- Publisher
- Springer-Verlag
- Year
- 1972
- Tongue
- English
- Weight
- 286 KB
- Volume
- 104
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
When barley aleurone layers are treated with gibberellie acid (GA3) in the presence of increasing concentrations (0.2-0.8 M) of malmitol, the rate of a2Pi incorporation into phospholipids becomes progressively inhibited. Malmitol does not affect this process in aleurone layers not treated with GAs, nor does it appreciably inhibit GA3-effected increases of 32Pi incorporation into organic phosphates or the activities of the particulate enzymes of the CDP-choline pathway. These results suggest that some of the early events controlled by GA a can be separated from later activities regulated by the hormone, including ~-amylase synthesis.
Gibberellic acid (GA3)-effected ~-amylase synthesis and secretion in barley aleurone cells commences after an initial lag period of 8-10 h (Varner and Chandra, 1964). There are, however, earlier events in barley aleurone cells which are controlled by the hormone and which may be required for the ultimate production and secretion of hydrolases. Jones (1969a) showed that proliferation of rough endoplasmic reticulum had occurred after 10 h of GA s treatment. Choline incorporation into a partially purified endoplasmic reticulum fraction (Evins and Varner, 1971) and a2Pi incorporation into phospholipids (Koehler and Varner, 1971) are enhanced by GA 8 after a 4-h lag period. Furthermore, increases in the activities of two key enzymes involved in lecithin biosynthesis are evident after only 2 h of GA 3 treatment (Johnson and Kende, 1971). Metabolic antagonists such as cyclohe~imide and actinomycin D, and abscisic acid inhibit these GA 3 responses to similar extents (Chrispeels