Dr. Hui Yang: Dept. of Molecular & Cell Biology

Symbiosis, or the co-existence of organisms, is a fundamental factor in maintaining the structure of the ecosystem, as well as in the development and evolution of species. Its importance has been increasingly recognized in various aspects of biological research and changed our perspectives on many topics. Instead of focusing solely on individual species, more and more studies are taking into consideration the influences from symbionts when investigating certain behavior of an animal, the evolution of specific traits, or structural changes in a population.

A unique case of symbiosis is the mutualistic relationship between the spotted salamander Ambystoma maculatum embryos and the green alga Oophila amblystomatis. The algae appear inside the salamander eggs during development and become so abundant that the entire egg clutch turns green (see attached picture). Recent discoveries revealed algal presence inside the embryonic cells. Such intracellular symbiosis has never been reported between animal and algal cells. It was also found that the embryo would turn down its immune defense to allow the presence of the algae. Does the embryo tolerate these green symbionts to obtain nutrients? Or maybe the algae protect the embryo from harmful bacteria? Early experiments showed that without algae, the survival/hatching rate of embryos dropped significantly. Further studies suggested that the algae may provide extra oxygen for the embryo to survive stressful conditions. However, to date, there is no direct evidence of material exchange between the algae and the embryo. Moreover, little is known about the influence of algae on the bacterial community inside salamander eggs, which plays a critical role in embryo survival and immune system development.

My research goal is to address these questions using two approaches: 1) track the fate of essential biomolecules such as sugars and amino acids that are produced by the algae, and 2) investigate the impact of algal symbiont on the bacterial community structure. For approach 1, I am currently working in Dr. Solange Duhamel’s laboratory at the University of Arizona to establish an Oophila laboratory culture labelled with stable isotopes (13C, 15N). For this approach, I will be working with collaborator Dr. John Burns at the Bigelow Laboratory for Ocean Sciences to prepare salamander samples that will be injected with 13C and/or 15N labeled Oophila. Further, I will collaborate with scientists at Stony Brook University and Arizona State University to visualize the isotopes in algae-inhabited salamander cells using nano-Raman molecular imaging and nanoscale secondary ion mass spectrometry (nanoSIMS), respectively. For approach 2,  I will visit Dr. Ryan Kerney’s laboratory at Gettysburg College and conduct a series of experiments in his laboratory to compare bacterial abundance and taxonomic diversity in eggs that harbor algae with eggs that do not have algae. With combined expertise of three collaborating laboratories and state-of-the-art technologies, we are expecting to answer some lingering questions and provide new insights in understanding the alga-salamander symbiosis.
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My interest in developmental and evolutionary biology grew during my PhD study while I was working on a group of microscopic invertebrates called rotifers. Specifically, I was interested in the ultrastructure and evolution of their extracorporeal sheath (a defensive structure secreted by some species of Superorder Gnesiotrocha). Fascinated by the intricate yet diverse design of nature, I decided to delve further into the field of development and evolution. Here at University of Arizona, my journey entered a new chapter. Along with new opportunities came great challenges and responsibilities. However, with the mentorship of Dr. Duhamel and the support from the university, especially the BIO5 Fellowship, I have been able to face those challenges and strengthen my skills for my future career. 

Ambystoma maculatum egg with the embryo and the green algae, Oophila amblystomatis

​Photo source:
Kerney R, Kim E, Hangarter RP, Heiss AA, Bishop CD & Hall BK. 2011. Intracellular invasion of green algae in a salamander host. Proceedings of the National Academy of Sciences 108:6497-6502.