Research Interests
Our group investigates the cellular and molecular interactions underlying mutualistic symbioses between cnidarians, such as corals and anemones, and their photosynthetic dinoflagellate symbionts Symbiodinium spp. We are interested in the establishment, maintenance and breakdown of these cooperative partnerships. We use several model associations in our studies, including a Hawaiian stony coral, Fungia scutaria, a tropical sea anemone Aiptasia pallida, a temperate sea anemone found on the Oregon coast, Anthopleura elegantissima, and a Red Sea soft coral, Heteroxenia fuscescens.
Symbiotic and aposymbiotic Anthopleura elegantissima
Onset of symbiosis: processes of recognition and specificity
We are examining the dynamic process of the onset of symbiosis during the cnidarian host larval stage. Most species must acquire symbionts anew with each generation and therefore must engage in a complex recognition and specificity process that results in the establishment of a stable symbiosis. We are using confocal microscopy and in situ hybridizations to examine the dynamics of first infection, such as the location and mechanism of algal uptake by host larvae. There is increasing evidence from other mutualistic endosymbioses that the inter-partner signaling pathways involved during the onset of symbiosis are homologous to those driving animal host/pathogenic microbe interactions. Therefore we are investigating the role of host innate immunity in the recognition process during the onset of symbiosis.
Fungia scutaria planula larva with resident Symbiodinium
(Larval length ~ 100 um)
Regulation and maintenance of symbiosis
We are interested in identifying genes that are up- or down-regulated specifically as a function of the symbiotic state in host cnidarians. We are employing a variety of functional genomics techniques, including degenerate primer RT-PCR, subtractive libraries, cDNA microarrays and RNAi, to identify and characterize these genes. We are especially interested in their function in the association. To date we have identified differentially expressed host genes that are involved in lipid metabolism, oxidative stress, cell adhesion, cell cycle control and control of cell proliferation. We have a developing model that symbiotic host cell survival is modulated by the presence of symbionts.
Confocal image of Fungia scutaria larva (host nuclei blue)
with resident Symbiodinium (red)
Symbiosis breakdown: coral bleaching
We are also interested in the breakdown of the symbiosis and the role of apoptosis in this process. Coral bleaching, or the loss of host animal pigment, is caused by the breakdown of the host animal/algal symbiont association. Bleaching is a growing global environmental problem and can cause the destruction of the entire reef ecosystems. Our group is investigating links between coral bleaching and apoptosis. As a first step we are characterizing apoptosis genes and apoptotic pathways in host animals, one of the first investigations of these critical cellular mechanisms to be performed on lower metazoans. To date we have identified a caspase and bcl-2 sequence. We are also examining the role that nitric oxide (NO) plays as a cytotoxic mediator of bleaching.
In situ hybridization using an actin probe of
a cryosection of a 1 mm Aiptasia pallida
Our group includes postdoctoral fellows, graduate students pursuing their PhDs through the Department of Zoology and undergraduates. I sponsor international students and postdoctoral fellows. Presently there are members from Venezuela, Uruguay, France, and the United Kingdom, as well as the USA.
We perform field work both along the Oregon Coast (see photo at top left) and at the Hawaii Institutue of Marine Biology, University of Hawaii's marine lab in Kaneohe Bay on Oahu (see photo at top right).
Collaborators:
Denis Allemand, PhD, Professor, University of Nice, Sophia Antipolis, Nice, France
Yehuda Benayahu, PhD, Professor, Tel Aviv University
Simon Davy, PhD, Senior Lecturer, Victoria University of Wellington, New Zealand
Douglas Green, PhD, Chair, Immunology, St. Judes Children's Research Hospital, Memphis, TN
Dave Krupp, PhD, Professor, Windward Community College, HI
John Pringle, PhD, Professor, Department of Genetics, Stanford University
This research program is supported by grants from the National Science Foundation.
