Worm Breeder's Gazette 11(4): 113

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Intercellular Transfer of Cytoplasmic Components into the Differentiating Gut Primordium

Olaf Bossinger and Einhard Schierenberg

As described earlier (WBG 10(3)), Lucifer Yellow (LY; ca.  450 
Daltons ) microinjected into early blastomeres of C.  elegans 
accumulates in the gut primordium during embryogenesis.  Improvement 
of our microinjection technique (Iontophoresis, Piezo-stepper for 
easier penetration), better visualization with a light-intensifying 
camera and application of additional fluorescent dyes allows us to 
study the process of dye incorporation into individual embryos and 
further development in more detail.  
Following injection, LY-CH spreads at first all over the embryo.  
After a few minutes it becomes coupled to granular cytoplasmic 
components (probably yolk granules).  During morphogenesis the dye 
accumulates in the gut primordium.  
LY-VS directly binds to cytoplasmic components of the injected cell 
such that a diffusion into neighboring cells does not take place and 
only the descendants of the marked cell show fluorescence.  
Nevertheless, with the beginning of morphogenesis a transfer into the 
gut primordium starts.  In the pretzel stage fluorescence is only 
present in the cytoplasm of the intestinal cells.  We assume that this 
transfer occurs via the extracellular space rather than directly from 
cell to cell.  On the one hand, if we inject into the AB cell of a 2-
cell stage, we only observe fluorescence in AB descendants (decreasing)
and gut cells (increasing) during the morphogenesis phase but never 
in muscle cells which are positioned between AB-derived hypodermis and 
By penetrating the eggshell with a laser microbeam during various 
phases of development, we can allow passage of LY from the surrounding 
medium into the perivitelline space.  No uptake of dye into the embryo 
is observed during the proliferation phase.  If the eggshell is 
penetrated during morphogenesis dye is instantaneously incorporated 
exclusively into the gut primordium.  Fluorescently labeled Dextrane (
4000 Daltons) is neither incorporated into the gut cells after 
injection nor after laser penetration at any stage.  If 2-cell embryos 
are laser-penetrated in a medium containing LY plus Cytochlasin, we 
observe an accumulation of dye in the gut precursor cell P1.  This 
demonstrates that cleavage is no prerequisite for this typical uptake 
process.  In addition we find that a reversal of cell size takes place 
(P1>AB) in such blocked 2-cell stages during development overnight, 
supporting our assumption that the accumulation of LY goes along with 
a transfer of other cytoplasmic components.
For interpretation of our observations two alternative explanations 
seem plausible.  On the one hand a transfer of yolk components into 
the gut primordium may take place, serving as a storage organ for 
postembryonic development.  Alternatively toxic waste products may be 
deposited in a water-insoluble form in the cytoplasm of the intestine. 
It appears likely that our observations are of general significance 
for nematode development because in two other species we have also 
observed such an uptake process.