Alexandra Harryman, Ph.D.


Biological Sciences 2012

Area of Doctoral Study: Biological Sciences

Undergraduate Institute: University of Maryland, Baltimore County

Research Advisor: Stephen Miller, Ph.D.

Current Position: Science Educator, Howard County Public School System

Description of Research

The transition from unicellular to multicellular life occurred within multiple lineages, including plants, animals, fungi, slime molds, brown algae, red algae, and green algae It is fairly easy to envision at least some of the ecological forces that might have driven the evolution of multicellularity and developmental complexity. Yet, we only have a few pieces to the puzzle of how multicellularity arose in any lineage because most known transitions to multicellularity with multiple cell types occurred so long ago (i.e. ~450-700 MYA for plants, and ~600 MYA for animals), and resolving phylogenies for lineages in which multicellularity has evolved has not been an easy task, nor has identifying the key molecular changes that fostered such transitions.
The ultimate goal of our lab’s research is to understand the molecular framework that fostered the evolution of multicellularity in Volvox carteri. We use this model organism because it lies at the other extreme of the spectrum of developmental complexity as its unicellular cousin Chlamydomonas reinhardtii, with whom it shared a common ancestor recently as 250 MYA. During this time, two of the most important functions carried out by C. reinhardtii unicells, reproduction and mobility, have been segregated into two cell types in V. carteri: reproductive gonidia, and sterile bi-flagellate somatic cells.
Developmental mutants allowed us to pinpoint regA as the gene responsible for the somatic fate in V. carteri. Recently, however, molecular analysis has uncovered a putative DNA binding domain in RegA that is encoded by a number of genes in C. reinhardtii and V. carteri, known as rls genes, for reg-like-sequences. The goal of my research is to determine the function of these genes using molecular genetics, as we believe that these genes serve roles in development that may be the link to understanding the molecular framework that allowed for the division of cell labor that accompanied multicellularity in V. carteri.