Areas of Specialization: Evolution of
Development
My research integrates phylogenetic, molecular evolution, and
developmental genetic approaches to understand evolutionary
mechanisms underlying plant development. I compare changes in
the number, sequence, expression, or function of genes across
different plant groups and determine how these changes shaped the
morphology and evolution of the groups. Currently, I am
specifically studying the evolutionary relationships of CYCLOIDEA,
a TCP transcription factor involved in floral symmetry. In
the case of TCP genes, there were three major duplications in the
CYCLOIDEA gene family that correlate with the explosion of diverse
but florally constrained eudicots (included about 70% of flowering
plant species). Additionally, there were two separate
duplication events of CYCLOIDEA, which correlate with a shift from
radially symmetric to bilaterally symmetric flowers within the
group Dipsacales.
Additionally, I examine changes in the expression of
morphologically important genes. For instance, CYCLOIDEA is
expressed in the upper petals of all currently examined bilaterally
symmetric flowers. There is a different pattern in a group I
study, however, Lonicera (honeysuckle), which has a flower with
four upper petals and one lower petal vs. the more common two upper
petals and three lower ones. This morphology shift is
correlated with a shift in expression, with one copy of CYCLOIDEA
found in the typical position in only the upper two petals and the
other copy in all four of the upper petals. I also plan to
compare the function and interaction of these genes and
proteins. The newest techniques include infecting plants with
a virus that knocks-down the expressed RNA from a gene. This
would allow me to examine the change in morphology when a certain
gene or gene family is effectively turned off.
My research ultimately aims to study how the interplay of the
TCP genes and their interacting patterns sets the developmental
pattern that determines the morphology of a flower.
Hawaiian Biogeography and Evolution – My lab is also interested in
the mechanisms of adaptive radiations in the Hawaiian
Islands. Hawaiian Scaevola provides a model clade to study
the genes involved in adaptive radiations. This is one of the few
adaptive radiations in plants with a completely resolved phylogeny,
reciprocally monophyletic species, and phenotypically diverse
morphologies. A limited amount of background molecular variation
(common in plants), suggests that this clade radiated through
changes in just a few genes. Candidate genes are now available for
many of the morphological changes in Scaevola, allowing us to
compare both sister species pairs and hybrid species pairs to
determine discrete genes that could have played a role in the
radiation of this group. For instance, Hawaiian Scaevola flower
color varies from white, yellow, brown, and purple, covering
different amounts of the petals in each species. The ROSEA pathway,
including a group of MYB genes, controls anthocyanin production and
is one of the better worked out pathways in plants. Changes in this
pathway could certainly affect these flower colors. Scaevola also
differs in inflorescence architecture (i.e., number of flowers),
which LEAFY has been shown to affect in Arabidopsis. Therefore,
studying genes such as ROSEA and LEAFY and their networks in
Scaevola could provide insight into how and why certain genes
change, allowing a template for adaptive radiations.