The simple liverwort provides new insights into plant evolution
Dr. Berger's lab uses Marchantia polymorpha to study how a special class of DNA-binding proteins, histones, have evolved to organize the genome. Marchantia is a common, easily cultivated liverwort that shows many characteristics of both liverworts and land plants; it is widely used in studies of physiology, anatomy, genetics, and perhaps most importantly, evolution.
In a study published today in the prestigious journal Cell, Fred Berger, one member of a diverse international team led by Dr. John Bowman from Monash University in Australia, sequenced and analysed the genome of Marchantia and found that that it retains more ancestral land plant characteristics than any plant alive today.
The colonization of land by plants was a major evolutionary event in Earth’s history, dramatically changing geochemical cycles and altering the evolutionary trajectories of other populations, such as animals. These early land plants evolved from freshwater algae, and most likely resembled three groups of modern plants, liverworts, hornworts, and mosses, which are collectively known as bryophytes.
The evolutionary relationship of the bryophytes is still under debate. However, fossils assigned to liverworts predate those of either mosses or hornworts, and evidence from systematics and phylogenetic studies suggest that the first plants colonizing terrestrial environments possessed attributes of liverworts. The new study shows that liverworts retained not only the anatomical characteristics of ancestral plants, but also the predicted genomics characteristics, especially with respect to regulatory genes. This is likely because Marchantia has not undergone multiple rounds of genome duplication, a process common in the evolutionary history of most land plants.
“Marchantia is becoming a fantastic model organism for many basic biological questions” says Dr. Berger. “The completion of this genome sequencing project should further enable these studies, and also help us understand how land-plants evolved.”
The project was a community-sequencing project with much of the sequencing done by the Joint Genome Institute (US Department of Energy) followed by genome analysis by a network of around 100 scientists from around the world with various interests.
Bowman JL, Kohchi T, Yamato KT et al. (2017) Insights into Land Plant Evolution Garnered from the Marchantia polymorpha Genome. Cell [epub].
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