Amazing stuff!
"An international team of researchers has uncovered a remarkable genetic phenomenon in lycophytes, which are similar to ferns and among the oldest land plants. ...
Homosporous lycophytes, a group of seedless vascular plants, show extraordinary genomic stability. The team sequenced the genomes of two species, Huperzia asiatica and Diphasiastrum complanatum, which diverged from a common ancestor about 350 million years ago (approximately when amphibians started to crawl onto land). ...
“This study opens a window into the past, showing us how remarkably stable the genetic makeup of these plants has been,” said Dr. Li Wang, co-author of the study. “It’s like finding a living fossil at the genetic level.” ..."
“This study opens a window into the past, showing us how remarkably stable the genetic makeup of these plants has been,” said Dr. Li Wang, co-author of the study. “It’s like finding a living fossil at the genetic level.” ..."
From the significance and abstract:
"Significance
Lycophytes occupy a critical phylogenetic position sister to all other vascular plants. Unlike seed plants, they comprise heterosporous (Selaginellaceae and Isoetaceae) and homosporous (Lycopodiaceae) lineages. Homosporous plants have long been known to possess large genomes with considerably more chromosomes than heterosporous counterparts. However, limited genomic resources for homosporous lycophytes have hindered efforts to identify precise differences underlying this fundamental distinction. Here, we assembled chromosome-level genomes of homosporous lycophytes, Huperzia asiatica and Diphasiastrum complanatum. Despite 350 Mya of divergence and independent whole genome duplications, synteny is remarkably well preserved between these genomes. This, combined with significantly reduced nucleotide substitution rates, suggests a contrasting mode of genome evolution between heterosporous and homosporous lycophytes.
Abstract
Homosporous lycophytes (Lycopodiaceae) are a deeply diverged lineage in the plant tree of life, having split from heterosporous lycophytes (Selaginella and Isoetes) ~400 Mya. Compared to the heterosporous lineage, Lycopodiaceae has markedly larger genome sizes and remains the last major plant clade for which no chromosome-level assembly has been available. Here, we present chromosomal genome assemblies for two homosporous lycophyte species, the allotetraploid Huperzia asiatica and the diploid Diphasiastrum complanatum. Remarkably, despite that the two species diverged ~350 Mya, around 30% of the genes are still in syntenic blocks. Furthermore, both genomes had undergone independent whole genome duplications, and the resulting intragenomic syntenies have likewise been preserved relatively well. Such slow genome evolution over deep time is in stark contrast to heterosporous lycophytes and is correlated with a decelerated rate of nucleotide substitution. Together, the genomes of H. asiatica and D. complanatum not only fill a crucial gap in the plant genomic landscape but also highlight a potentially meaningful genomic contrast between homosporous and heterosporous species."
A Window into Plant Evolution: The Unusual Genetic Journey of Lycophytes (Boyce Thompson Institute)
Diphasiastrum complanatum, Schwäbisch-Fränkische Waldberge, Germany
No comments:
Post a Comment