National Science Foundation
Directorate for Biological Sciences
Division of Integrative Organismal Biology

Integration of Development and Physiology: Mechanisms Shaping Animal
Phenotypes


Dear Colleague,

A workshop entitled "An Integrative Developmental
Biology" was held in November, 2004, and sponsored by the
Division of Integrative Organismal Biology (IOB) in the Directorate
for Biological Sciences at the National Science Foundation. That
workshop drew our attention to what we now recognize as an emerging
area of research that spans the traditional areas of developmental
biology, and ecological and evolutionary physiology presently
supported by IOB. With this letter we wish to inform a broader
community of scientists about this emerging area.

The workshop participants took a broader view of animal ontogeny
than is often held by developmental biologists, as described in the
workshop report, http://www.nsf.gov/pubs/reports/idbwsreport.pdf.
This broader view comprises more than the unfolding of a genetic and
signaling cascade triggered at fertilization. The unfolding of the
animal phenotype, its variation within a species and the causes of
the differences between species, are much more complex and less
understood processes. This view considers the physiological
regulation and environmental inputs as well. The general questions
that follow are in some cases taken directly from the workshop
report, and reflect the scope of this emerging effort.

How are complex phenotypes built?

It is well known that complex phenotypes are determined through the
interaction of many and diverse genetic and environmental factors
whose effects accumulate over long periods of time. Yet, the
development of cells and tissues are typically studied in isolation
and over brief time periods. As a consequence, little is known about
how the development of different cells and tissues is integrated to
produce complex organs and physiological systems, and how the
ever-changing organism remains functionally well integrated
throughout its development.

What are the interacting developmental and physiological bases of
phenotypic variation?

The genetic and environmental determinants of development and
physiology naturally vary in space and time. As a consequence,
phenotypic variation has both environmental and genetic causes.
Physiological variation as a consequence of environmental variation
is well studied. These latter studies have described mechanisms of
short-term physiological adjustments to environmental challenge
(i.e., acclimation, phenotypic plasticity) within the lifetime of
the animal. Fewer studies have mechanistically connected genetic
variation, physiological variation, and evolutionary physiological
adaptation to the environment. Although the relative effects of
genetic and environmental variation can be assessed statistically,
the developmental mechanisms through which normal genetic and
environmental variation produce natural phenotypic (i.e.,
morphological) variation are virtually unexplored and therefore
remain poorly understood. Clearly, the interaction of developmental
and physiological processes produce natural variation in
morphological and physiological sets of characters, and both of
these kinds of processes are influenced by genetic and environmental
variables.

Thus an important and emerging conceptual area is focused on
mechanistic processes at the interface of development and physiology
to understand phenotypic variation.

How are developmental and physiological systems integrated?

As development proceeds and the animal grows in size, the
coordination of development of distant parts becomes increasingly a
problem of physiology rather than cell biology. Integration of
development must occur on a spatial scale, in that developmental
progression to different stages in a life cycle must be regulated.
The mechanisms by which spatial and temporal coordination of
development occur are largely unknown.

Additional questions that are relevant to this new area are shown
below:

What are the mechanisms of homoplasy? What are the mechanisms by
which the same suite of physiological or morphological characters
arises despite variations in developmental mechanisms?

How do variations in gene regulatory networks express themselves in
altered animal phenotypes across and within species?

How does a given developmental genetic mechanism give rise to
variations in morphological or physiological states within or
between species?

What are the physiological determinants of developmental
progression?

Does physiological variation differentially influence developmental
genetic mechanisms, and lead to phenotypic variation in animals
within and between species?

As we become aware of other emerging areas of research within the
Directorate for Biological Sciences, through workshops or other
means, we intend to alert the broad community of scientists about
them as a way to increase consideration of, and eventual
participation in, these newly emerging areas.



Sincerely,


James P. Collins
Assistant Director

Contact information:

Judith Plesset                   William Zamer
Program Director,               Program Director
Developmental Systems     Environmental and Structural Systems
jplessest@nsf.gov              wzamer@nsf.gov
(703) 292-8417                   (703) 292-8421