''Selaginella moellendorffii'' is a

lycophyte The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest lineag ...

that is an important

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

, especially in

comparative genomics Comparative genomics is a branch of biological research that examines genome sequences across a spectrum of species, spanning from humans and mice to a diverse array of organisms from bacteria to chimpanzees. This large-scale holistic approach c ...

. ''S. moellendorffii'' is a member of an ancient

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

lineage that first appeared in the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

some 400 million years ago. They would later form a dominant part of the world's flora during the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

period. They have a number of unusual and/or "primitive" features, such as rudimentary leaves ( microphylls), ubiquitous dichotomous branching,

heterospory Heterospory is the production of spores of two different sizes and sexes by the sporophytes of land plants. The smaller of these, the microspore, is male and the larger megaspore is female. Heterospory evolved during the Devonian period from isos ...

, and the

ligule A ligule (from "strap", variant of ''lingula'', from ''lingua'' "tongue") is a thin outgrowth at the junction of leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above g ...

. As the earliest diverging group of modern vascular plants, they are essential to understanding the evolution of plants as a whole.

Morphology and anatomy

''Selaginella moellendorffii'' exhibits unique morphological features characteristic of lycophytes. The plant possesses microphylls—small leaves with a single unbranched vein—and displays dichotomous branching patterns. Its vascular system comprises protosteles, and roots arise from specialized structures called rhizophores. These features reflect its ancient lineage among vascular plants.

Genome sequencing

The nuclear genome size is approximately 100 mega base pairs, one of the smaller

genome size Genome size is the total amount of DNA contained within one copy of a single complete genome. It is typically measured in terms of mass in picograms (trillionths or 10−12 of a gram, abbreviated pg) or less frequently in daltons, or as the tot ...

s found for any plant species. The genome has been sequenced and assembled by the United States Department of Energy's

Joint Genome Institute The Joint Genome Institute (JGI) is a scientific user facility for integrative genomic science at Lawrence Berkeley National Laboratory. The mission of the JGI is to advance genomics research in support of the United States Department of Energy ...

(DOE JGI). Community annotation of the genes and other elements of this genome began in September 2007. Gene content of ''S. moellendorffii'' and diverse other

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

have shown that the transition from

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the se ...

- to

sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...

-dominated life cycle entailed the addition of fewer new genes than the move from nonseed vascular plants (

s) to

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s (angiosperms). Hecht ''et al.'', 2011 finds that ''S. moellendorffii'' has the highest

guanine Guanine () (symbol G or Gua) is one of the four main nucleotide bases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). In DNA, guanine is paired with cytosine. The guanine nucleoside ...

cytosine Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attac ...

content of any

organellar DNA Organellar DNA (oDNA) is DNA contained in organelles (such as mitochondria and chloroplasts), outside the nucleus of eukaryotic cells. * Mitochondria contain mitochondrial DNA * Plastids (e.g., chloroplasts) contain plastid DNA Inheritance of ...

. Its

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

is 68% G+C; both are typically rare components of any organellar DNA.This review cites

Genomic insights

''S. moellendorffii'' was the first non-seed vascular plant to have its genome sequenced. The genome is compact, approximately 100 Mbp in size, and contains essential insights into early vascular plant evolution. Comparative studies highlight the limited number of new genes needed for the shift from gametophyte to sporophyte dominance, and further from lycophytes to flowering plants.

Ecology and distribution

''Selaginella moellendorffii'' is native to subtropical Asia and grows in moist, shaded forest floors. It is commonly found in low-elevation broadleaf forests, including those in Taiwan. The species exhibits moderate desiccation tolerance, allowing it to persist in fluctuating environments.

Evolutionary significance

As one of the earliest diverging vascular plant lineages, ''S. moellendorffii'' is a valuable model for understanding the evolution of plant form and function. Its genome, morphology, and physiological traits shed light on the transition from non-vascular to vascular systems in land plants.

Life cycle and reproduction

''S. moellendorffii'' is heterosporous, producing distinct megaspores and microspores. This results in the development of separate female and male gametophytes, a feature that distinguishes it from homosporous species. Heterospory is considered a significant evolutionary advancement in the diversification of vascular plant reproductive strategies.

References

External links

* American Society for Plant Biolog
''Selaginella'' education page

''Selaginella'' genomics website
- contribute to the genome annotation
Purdue University's ''Selaginella'' Wiki
{{Taxonbar, from=Q3205665 moellendorffii