Project 3
The Role of Polyamines
in the Senescence of the Hepatic Marchantia polymorpha
(Pis: Nicholas Maravolo and
Jerrold Lokensgard,)
Polyamines are responsible for the inhibition of premature
cell death in plants through cell membrane stabilization. Because they are polycationic
they bind strongly to negatively charged cell components, such as proteins,
membranes, RNA and DNA. Inhibition of
premature cell death is made possible through the prevention of catabolic
enzyme leakage from storage vesicles.
Polyamine concentrations are most abundant in young tissue and decrease
rapidly with age as ethylene concentration increases. We have hypothesized that
internal premature cell death signals somehow suppress the production of
polyamines while elevating the levels of the ethylene associated with cell
senescence. This main objective of this
project was to identify and characterize internal polyamines of Marchantia polymorpha.
Summary of Research Results
Earlier work in our laboratory by Stanislaus showed that
externally applied polyamines suppressed premature cell death. A questionable identification of internal
polyamines was conducted in our lab by R. Geck and
also by M. Hoskins. This year's Merck
Scholar, Adam Locke, used gas chromatography and mass spectroscopy on polyamine
derivatives to establish the retention times for spermine,
spermidine, putrescine, cadaverine, and hexanediamine. Derivatized putrescine consistently came through the chromatographic
column with a retention time of 8.47 min.
Cadaverine had a standard retention time of
10.67 min. Hexanediamine
had a standard retention time of 12.33 min. and spermidine
had a retention time of 19.52 min. Spermine exhibited a standard retention time of 28.84
min. The system worked fine for
identifying these chemicals. However,
when Adam tried to synthesize pentafluoropropionic
derivatives of the standards, and then run them through a DOWEX ion exchange
column, the polyamines could not be retrieved.
Adam is refining this procedure during the current academic year so he
can ultimately isolate and quantify internal Marchantia polyamine derivatives,
and then evaluate their role in premature cell death.