Charles F. Delwiche
University of Maryland - College Park
Current research activities:
The Delwiche lab's research focuses on the reconstruction of early events
in the evolution of photosynthetic organisms, with emphasis on the evolutionary
origin of embryophytes (land plants) from green algae, and on the endosymbiotic
origin of plastids. Current projects are: 1) systematics and taxonomy
of charophycean green algae, with current funding from NSF grant DEB-9978117,
"PEET: a unified approach to systematics of basal streptophytes (charophycean
green algae)", and 2) the molecular biological basis for the incorporation
of the peridinin-type dinoflagellate plastid into the host cell, funded
in part by a grant from the Alfred P. Sloan Foundation,and in part by
NSF grant MCB-9984284, "Plastid-associated genes in dinoflagellates
identified by cDNA screening and expression analysis."
The basal streptophytes include five orders of green algae that are
very closely related to land plants (embryophytes; Graham, Delwiche et
al. 1991). The state of systematic work in each of these orders is different,
in large part because of their very different morphologies, and because
they were not historically classified together. We are working to develop
a uniform classification of these organisms, to develop a definitive phylogeny
for the group, and to improve the understanding of their structure and
biology. We have determined that some recent studies have been misled
by sequencing artifact (Cimino, Karol et al. 2000), and are investigating
the influence of methodological issues on the reconstruction of phylogeny
within the basal streptophytes. We are also performing molecular phylogentic
and morphological studies in each of the orders within the group, and
will use these data to develop monographs or addenda to existing monographs,
as is appropriate depending upon the current state of taxonomy in each
order.
A review of the current state of knowledge concerning the origin and
evolution of plastids is presented by Delwiche (Delwiche 1999). In our
work on dinoflagellates, we have succeeded in independently isolating
several genes that appear to be from the peridinin-type plastid genome,
and are currently working to verify their localization to the plastid.
In the course of this project we have participated in the identification
of tertiary plastids in one group of dinoflagellates (Tengs, Dahlberg
et al. 2000), and in the development of molecular methods for the identification
of Pfiesteria piscicida (Oldach, Delwiche et al. 2000), and a manuscript
discussing the evolution of pigmentation in peridinin-type plastids and
other chlorophyll-c containing plastids is currently in preparation. We
are now moving into a new phase of this project, in which we will apply
genomic methods to investigate the organization of the dinoflagellate
plastid genome and the genetic integration of the plastid into the host
cell. Because the nuclear genome of most dinoflagellates is exceptionally
large (as much as 100 fold larger than the human genome), we are using
a cDNA approach to examine genome complexity and expression. One key question
is why these organisms have such remarkably large genomes; it is not clear
that the complexity of the genome matches its large size. To understand
the organization of the dinoflagellate genome, it will also be important
to determine whether the genome is polyploid, and the extent to which
dinoflagellate genes are encoded as polygenes.
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