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Every
living plant cell and animal cell is surrounded by a membrane. These
cellular membranes contain receptor molecules that serve as the cell’s
eyes and ears, and help it communicate with other cells and with the
outside world.
The
receptor molecules accomplish three basic things in the communication
process: 1) recognize an outside signal, 2) transport that signal across
the cell’s membrane and 3) initiate the reading of the signal inside
the cell and then initiate the cell’s response to that signal. These
steps are collectively known as transmembrane signaling.
Transmembrane
signaling in animal cells has been significantly more studied and
observed than that in plant cells. But now, with support from the
National Science Foundation, researchers from Joanne Chory’s laboratory
at the Salk Institute have published new observations about
transmembrane signaling in plants; their paper appears in the June 12,
2011, advanced online edition of Nature.
According
to the study, transmembrane signaling mechanisms used by plants differ
from those used by animals. Specifically, Michael Hothorn of the Salk
Institute reports that a small steroid molecule on the outside of the
plant cell assists in the transmembrane signaling process. By contrast,
this sort of molecule and its receptor is generally located inside the
nuclei of animal cells.
While
studying transmembrane signaling in plants, Hothorn and colleagues
observed the steroid, shown in yellow, attach to a membrane-bound
receptor, shown in blue. This attachment enabled the steroid’s
counterpart–a co-receptor protein, shown in orange–to bind to the blue
receptor. Once bound, the orange co-receptor and the blue receptor
become glued together by the yellow steroid, allowing their
intracellular domains to touch and initiate communication.
In the case observed by Hothorn, transmembrane signaling initiated plant growth.
