Tree fern genome provides insights into its evolution
Alsophila spinulosa in a forest. Credit: Quanzi Li

Our world has evolved from land plants. Ferns have undergone a number of changes in order to survive on land. Researchers have characterized the genome arrangement of tree ferns, which sheds new light on how fern evolved.

The invention of their vascular systems was one of the major events in the evolution of land plants. The xylem and phloem are part of these systems. The xylem helps move water to the stems and leaves, while the phloem helps move sugars from one place to another. Lignin is a supportive structural material that provides rigidity to wood and bark. The researchers wanted to know how these systems evolved in fern.

"Ferns are the earliest vascular plants, and lignified cell walls were a key innovation during the evolution of these plants," said a professor of plant biology. The study has improved our understanding of how plants grow.

The researchers studied the genetics of the flying spider-monkey tree fern Alsophila spinulosa. They found that the two genes that were highly expressed in xylem were related to the formation of xylem-specific cells.

The researchers measured the levels of the two compounds that are not required for growth or reproduction in ferns. Lignin made up 40% of the stem cell wall, according to their findings. Wood usually has 25%. Alsophilin is a new secondary metabolite found in the xylem.

The genes involved in the synthesis of alsophilin were identified by us.

The researchers compared the genomic sequence of A. spinulosa to other members of the same species. They were surprised to discover that there were six different populations. The researchers looked at the history of the fern population and found that there were two times when the population decreased dramatically. The first one happened between 35.6 and 34.5 million years ago, and the second happened between 0.7 and 0.7 million years ago.

The analysis of genomes and Lignin composition from a broader collection of ferns will help us understand the role of Lignin in the earliest stages of the plant family. We would like to increase the number of locations and sample sizes for the analysis.

The analysis was done at the State Key Laboratory of Tree Genetics and Breeding in Beijing, China.

More information: Xiong Huang et al, The flying spider-monkey tree fern genome provides insights into fern evolution and arborescence, Nature Plants (2022). DOI: 10.1038/s41477-022-01146-6 Journal information: Nature Plants