A central problem
in biology is to
understand the robustness of biological processes when faced with
random
fluctuations, varying environments or genetic changes, and to evaluate
the
evolutionary consequences of this robustness. Using well-studied model
systems,
it is now possible to ask, not only which
genes and proteins regulate them, but i) how
this is done in a quantitative
manner, ii) how stable the system is
when faced with perturbations, and iii) what are the evolutionary
dynamics of the molecular network within the species
and among different species. We address these questions using as a
model the
molecular network that underlies a simple and well-studied
developmental
process: vulval precursor cell specification in the nematode worm Caenorhabditis elegans.
In this system, three different
developmental cell
fates are specified within a row of six cells, using an intercellular
signaling
network that produces a stable output as the spatial cell fate pattern
in this
row of six cells. The correct fate pattern is required for normal vulva
formation, and therefore for copulation and egg-laying.
We study the precision and evolution of
the
developmental mechanisms that underlie vulva development in different
nematode
species and among C. elegans wild
isolates, and their evolvability (capacity to evolve) upon random
mutation.
Striking results are:
- the developmental
mechanisms that lead to this pattern vary between and within species,
whereas the final spatial pattern of vulva precursor cell fates is
robust and invariant;
- the evolvability
of different vulva development features varies between species, and
correlates with the features that actually vary among wild isolates of
each species or closely related species.
