exchemist
Valued Senior Member
I was alerted to the following research by another science forum I subscribe to:
https://www.science.org/doi/10.1126/science.adk1075
It is well-known that various plants, e.g. clover, peas and beans, make use of a symbiosis with nitrogen-fixing bacteria in their root nodules. This new research has discovered a marine alga that can fix nitrogen by means of an organelle actually within its own cells. The researchers dub this the "nitroplast", by analogy with the chloroplasts that enable photosynthesis. It looks as if what has happened is that a nitrogen-fixing bacterium has first become an endosymbiont, living within the alga, and then has become incorporated into the actual machinery of the alga's own cells.
This may shed some light on very early evolutionary processes by which other organelles may have arisen, by being first endosymbionts and then getting integrated into the cell. While the nitroplast still has DNA of its own, the template for some of the proteins that the former endosymbiont needs is now in the cell nucleus. When these proteins are manufactured by the cell, a label is attached to them which gets them picked up by the "nitroplast". The cycle of cellular division of the nitroplast has also become harmonised with that of the cell, so that when one divides the other one does too.
A key feature of the change seems to be this progressive migration of at least parts of the genetic coding needed for replication, from the endosymbiont to the nucleus of the host cell. Amazing!
I understand the prevailing explanation for the evolution of the mitochondrion is that it was a bacterium that somehow became assimilated by the cells of eukaryotes. They too still retain some of their own DNA, separate from the cell nucleus. Apparently, mitochondrial DNA resembles bacterial DNA. But this "nitroplast" seems to have evolved much more recently, as the process of integration within the cell is not so pronounced.
Perhaps investigation of this will help us understand how eukaryotes acquired other organelles in the long distant past.
https://www.science.org/doi/10.1126/science.adk1075
It is well-known that various plants, e.g. clover, peas and beans, make use of a symbiosis with nitrogen-fixing bacteria in their root nodules. This new research has discovered a marine alga that can fix nitrogen by means of an organelle actually within its own cells. The researchers dub this the "nitroplast", by analogy with the chloroplasts that enable photosynthesis. It looks as if what has happened is that a nitrogen-fixing bacterium has first become an endosymbiont, living within the alga, and then has become incorporated into the actual machinery of the alga's own cells.
This may shed some light on very early evolutionary processes by which other organelles may have arisen, by being first endosymbionts and then getting integrated into the cell. While the nitroplast still has DNA of its own, the template for some of the proteins that the former endosymbiont needs is now in the cell nucleus. When these proteins are manufactured by the cell, a label is attached to them which gets them picked up by the "nitroplast". The cycle of cellular division of the nitroplast has also become harmonised with that of the cell, so that when one divides the other one does too.
A key feature of the change seems to be this progressive migration of at least parts of the genetic coding needed for replication, from the endosymbiont to the nucleus of the host cell. Amazing!
I understand the prevailing explanation for the evolution of the mitochondrion is that it was a bacterium that somehow became assimilated by the cells of eukaryotes. They too still retain some of their own DNA, separate from the cell nucleus. Apparently, mitochondrial DNA resembles bacterial DNA. But this "nitroplast" seems to have evolved much more recently, as the process of integration within the cell is not so pronounced.
Perhaps investigation of this will help us understand how eukaryotes acquired other organelles in the long distant past.
