Vegetable LUCA: the first LUCA. Science blog 117th
At the end of his work OnÂ The Origin Of Species Charles DarwinÂ wrote: “There is grandeur in this view of life, with its several powders, having been originally breathed into a few forms or into one…”.
Charles Darwin was defining -even without naming them- a set of life forms that coexisted for 600 million years (between 4100 and 3500 million years ago), which finally materialized in Archaea, Bacteria and Eukaryota; or a unique form that has been named Last Universal Common Ancestor (LUCA).
In this post, we will attempt to conceptually connect both groups starting from a different ordering criterion. In this era, all living beings can be grouped into two entities: those capable of producing their own food from an external energy source, and those that need the food produced by the previous ones as a source of energy. We will call the former “plant cells” and the latter “animal cells“.
Vegetable LUCA and Animal LUCA
One can consider that all plant cells come from a vegetable LUCA and all animal cells come from an animal LUCA. Considering that the animal LUCA depends on the vegetable LUCA for its feeding, it is unquestionable that the vegetable LUCA had first to exist. One that note, the following questions arise: Was the formation of Animal LUCA independent of Vegetable LUCA? Or was Animal LUCA necessarily formed from Vegetable LUCA?
Even though animal and plant cells have many functions in common, circular DNA of plant cells has more genetic information and other non-codified “abilities” than the animal cells circular DNA. Therefore, it seems more probable that the formation of animal LUCA derived from vegetable LUCA.
Such hypothesis makes plausible to establish the dependence of animal kingdom on the vegetable one and, at the same time, the relation in the community of biochemical processes between both types of cells. Thus, the abilities of producing oxygen, carbohydrates and essential amino acids are exclusive to plant cells. The loss of these capacities would be caused by the loss in size of the animal circular DNA.
This hypothesis has opened the way to focus our current research on three experimental lines
(1) Ability of the plant circular DNA to “selectively attract” amphoteric and bipolar molecules to its surface in order to form a primitive cell membrane.
(2) Ability of this structure to form a vacuum capable of hosting an incipient cytoplasm.
(3) Ability of DNA to form RNA as baseline towards the first ribosomal organelle.
In future blog posts we will report the results of the aforementioned investigation.