ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The specific activities of 6 enzymes, which are involved in the synthesis and catabolism of membrane lipids, were monitored in plasma membranes isolated from petunia petals during senescence. These included phosphatidylinositol (PI) kinase (EC 2.7.1.67), phosphatidylinositol monophosphate (PIP) kinase (EC 2.7.1.68). diacylglycerol (DAG) kinase (EC 2.7.1.107), phospholipase A (EC 3.1.1.4) and PIP- and PIP2-phospholipase C˙(EC 3.1.4.3). Using endogenous substrate, the [32P]PA and [32P]PIP2 formation increased to 140 and 200%, respectively, of the day 1 value by 4 days after harvest. There was no significant change in [32P]PIP formation during the same time period. On the fifth day the petals wilted and the [32P]PA and [32P]PIP formation declined significantly. In contrast, the [32P]PIP2 formation remained high in the day 5 petals. When the lipid kinase activities were assayed in the membranes in the presence of exogenous substrate the specific activity of all of the enzymes increased. and the changes in [32P]PA production over the 5-day period were similar to those observed with endogenous substrate. When exogenous PI and PIP were added, however, there was no longer an increase in [32P]PIP2 formation by plasma membranes of day 4 petals and [32P]PIP formation significantly decreased. The relative decrease in PIP and PIP2 formation by day 4 membranes when exogenous substrate was added may have resulted from differences in the lipase activities in the day 1 and day 4 membranes. The plasma membrane A-type phospholipase activity increased throughout the 5 day period, and phospholipase C activity increased two-fold between day 1 and day 4. Such changes in the metabolism of the plasma membrane lipids during flower senescence would affect the ability of the petals to use inositol phospholipid-based signal transduction pathways.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1994.tb00388.x
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