A team of researchers has cracked the genomic code of the beginning of plant life on land, which happened about 550 million years ago.
The team of researchers co-led by the University of Nebraska–Lincoln computational biologist Yanbin Yin has identified the genomic code that led to all kinds of terrestrial life forms, including humans.
The study focused on four genomes of filamentous Zygnematophyceae, which are the algal sisters of land plants. The researchers inferred traits in the ancestor of Zygnematophyceae and land plants that might have ushered in the conquest of land by plants.
The first plants on land
The first land plants (Embryophyta) emerged from within the clade of Streptophyta about 550 million years ago. The closest relatives of land plants, as per the study, are Zygnematophyceae algae, with more than 4,000 described species arranged into five orders.
The research paper states that the Zygnematophyceae possess adaptations to withstand terrestrial stressors, such as desiccation, ultraviolet light, freezing, and other abiotic stresses. The nature of their response to the terrestrial stressors reveals that they predate the origin of Embryophyta.
By using comparative genomics, researchers tried to pinpoint the genetic innovations of the earliest land plants. The research also sheds light on the co-expression of genes that were developed and expanded in the last common ancestor (LCA) of land plants and Zygnematophyceae.
Using the latest DNA sequencing techniques, the researchers generated a complete, chromosome-scale genome for the algae.
Prior to this, only the genomes of unicellular Zygnematophyceae had been sequenced. This study was, therefore, the first chromosome-level genome assembly for this class of algae.
The evolution story
“This is an evolution story,” said Yanbin. He went on to add that “it answers the fundamental question of how the earliest land plants evolved from aquatic freshwater algae.”
Genome sequencing is the process of determining an organism’s complete genetic material (DNA), which is assembled into a computational representation.
The researchers assembled four multicellular Zygnema strains using two from an algae culture collection at the University of Texas Austin and two from the University of Gottingen in Germany.
Comparing the genomes with those of other plants and algae, the researchers uncovered the genetic innovations employed by Zygnema.
The result
“Our gene network analyses reveal co-expression of genes, especially those for cell wall synthesis and remodifications that were expanded and gained in the last common ancestor of land plants and Zygnematophyceae,” Yin said.
The researchers said the discovery will lead to further studies that could be significant for bioenergy, water sustainability, and carbon sequestration.
“Not only do we present a valuable, high-quality resource for the entire plant scientific community, who can now explore these genome data, our analyses uncovered intricate connections between environmental responses,” said Jan de Vries, co-corresponding author from the University of Gottingen.
The study was published in the journal Nature Genetics.
