The Genome of a Tiny Fern:  Life’s Amazing Complexity

By Shlomo Maital

  The New York Times’ science writer Carl Zimmer has a wonderful piece today, about the incredible complexity (and beauty) of Nature.  It is about the remarkable discovery by Dr. Jaume Pellicer, a Spanish biologist.  Pellicer holds the world record, with a graduate student Pol Fernandez, for discovering the plant species with the largest genome ever known:  160 billion pairs of DNA letters (over 50 times more than humans!).  Its name:  Tmesipteris oblanceolate, a tiny 2-3 inch high jungle fern:

        “Dr. Pellicer knew that related fern species grew on a few Pacific islands. In 2016, he began making plans for an expedition to Grande Terre, part of the archipelago known as New Caledonia.  It wasn’t until 2023 that he finally made it to the island. He collected a number of species along with a team that included colleagues from Kew, his graduate student Pol Fernández and local plant experts.

  “Back in Barcelona, Mr. Fernández was startled to discover that Tmesipteris oblanceolata’s genome contained about 160 billion pairs of DNA letters. Thirteen years after Dr. Pellicer had discovered a record-breaking genome, his graduate student was also experiencing the thrill of breaking the record.”

     Why is this little fern’s genome so complex?  How does this help it compete and survive, in survival-of-the-fittest?  Not clear. It may be just an “error” – DNA duplicates itself, in reproduction, and sometimes creates additional unnecessary copies.

     Bigger genomes are a burden for cells.  Because, inside cells, the genes have to have food (energy).  So smaller genomes may be better for evolutionary success.

           Zimmer provides a really interesting glimpse into the science of the genome:

          “…Genomes are much weirder than scientists had expected. We carry about 20,000 protein-coding genes, for example, but they make up only 1.5 percent of the 3 billion pairs of letters in our genome.  Another nine percent or so is made up of stretches of DNA that don’t encode proteins but still carry out important jobs. Some of them, for example, act like switches to turn neighboring genes on and off.  The other 90 percent of the human genome has no known function. Some scientists have an affectionate nickname for this vast quantity of mysterious DNA: junk.”

          Junk????  Really?   Some people think that is what is on my work desk.  But everything on it, I am certain, has a real purpose – though, mostly, as yet undiscovered.

           Nature is amazingly complex.  Did all this incredible genomic complexity occur, from a bunch of random chemicals swimming in a warm sea?  As a believer,  I don’t really think so.  How about you?