UCSC Scientists Discover First Nitrogen-fixing Organelle
The UC Santa Cruz research team, from left to right: Esther Mak, Jonathan Zehr, Kendra Turk-Kubo and Tyler Coale
In recent groundbreaking research, a group of scientists have identified the first known example of a nitrogen-fixing organelle within a eukaryotic cell, which they have named the "nitroplast." This discovery is notable as it represents only the fourth instance of primary endosymbiosis recorded in history—a process whereby a prokaryotic cell is engulfed by a eukaryotic cell, eventually becoming an integrated organelle.
According to Tyler Coale, a postdoctoral scholar at UC Santa Cruz and lead author of one of the key studies, this phenomenon is incredibly rare and significant for the evolution of complex life; similar processes in history led to the development of mitochondria, chloroplasts, and a microbe akin to a chloroplast. The nitroplast, discovered after years of study and a certain amount of fortune, marks a new instance of a eukaryotic cell hosting a nitrogen-fixing organelle.
A light microscopy image shows the marine haptophyte algae Braarudosphaera bigelowii with a black arrow pointing to the nitroplast organelle. (Photo credit: Tyler Coale)
This breakthrough resulted from the collaborative efforts of researchers, including a key discovery in 1998 by Jonathan Zehr, a distinguished professor of marine sciences at UC Santa Cruz, and the extensive cultivation efforts of Kyoko Hagino, a paleontologist at Kochi University in Japan.
Their research reveals that the growth of UCYN-A, the cyanobacterium that became the nitroplast, and its algal host are interdependent, supporting the classification of UCYN-A as an organelle based on its functional integration and the protein exchange with its host cell. This discovery has profound implications for our understanding of cellular evolution and the potential for biotechnological applications in areas like agriculture and environmental conservation. This discovery not only challenges existing paradigms of endosymbiosis but also opens new avenues for biotechnological applications.