Sk. Roberts et al., THE ROLE OF CA2-TRANSDUCTION FOLLOWING FERTILIZATION IN FUCUS-SERRATUS( IN SIGNAL), Journal of Experimental Biology, 184, 1993, pp. 197-212
The marine brown alga Fucus serratus represents one of the few multice
llular plant species in which the process of fertilization can be stud
ied relatively easily. Fertilization marks the onset of a cascade of e
vents associated with egg activation. Fertilization in Fucus serratus
bears several superficial similarities to fertilization in several ani
mal systems. The essential features of Fucus serratus egg activation a
re compared with those of protostome and deuterostome animal systems.
Ca2+ is required for egg activation in Fucus serratus and cytosolic [C
a2+] changes can be observed in fertilizing eggs. However, these are s
mall and variable in comparison with those occurring in deuterostomes,
and fertilization can proceed normally in the absence of any global c
ytosolic Ca2+ transients. A model for egg activation in Fucus serratus
is presented, invoking a role for both Ca2+ influx and localized prop
agation of the sperm signal around the plasma membrane by an as yet un
identified mechanism. Polarity in Fucus serratus is acquired a conside
rable time after fertilization and the role of cytosolic Ca2+ gradient
s in the acquisition and expression of polarity is discussed. The prob
lem of the signals associated with the onset of the cell cycle in the
fertilized Fucus serratus egg is also addressed.