Abstract
BackgroundThe lycophytes are an ancient lineage of vascular plants that diverged from the seed plant lineage about 400 Myr ago. Although the lycophytes occupy an important phylogenetic position for understanding the evolution of plants and their genomes, no genomic resources exist for this group of plants.ResultsHere we describe the construction of a large-insert bacterial artificial chromosome (BAC) library from the lycophyte Selaginella moellendorffii. Based on cell flow cytometry, this species has the smallest genome size among the different lycophytes tested, including Huperzia lucidula, Diphaiastrum digita, Isoetes engelmanii and S. kraussiana. The arrayed BAC library consists of 9126 clones; the average insert size is estimated to be 122 kb. Inserts of chloroplast origin account for 2.3% of the clones. The BAC library contains an estimated ten genome-equivalents based on DNA hybridizations using five single-copy and two duplicated S. moellendorffii genes as probes.ConclusionThe S. moellenforffii BAC library, the first to be constructed from a lycophyte, will be useful to the scientific community as a resource for comparative plant genomics and evolution.
Highlights
The lycophytes are an ancient lineage of vascular plants that diverged from the seed plant lineage about 400 Myr ago
Genome size estimates The approximate genome sizes of several lycophyte species were determined by cell flow cytometry using as an internal standard the nuclei of other plants or cells with genomes of known sizes (Table 1)
The three estimates of S. moellendorffii genome size (Table 1) vary depending on species used as the internal standard
Summary
The lycophytes are an ancient lineage of vascular plants that diverged from the seed plant lineage about 400 Myr ago. The three orders of lycophytes that remain from this period include the homosporous Lycopodiales, the heterosporous Selaginellales and the heterosporous Isoetales. All of these plants are distinguishable from ferns and flowering plants by the presence of microphylls (as opposed to euphylls), the absence of leaf gaps and the absence of lateral roots. Based upon the fossil record, the lycophytes are thought to have emerged during the early Devonian about 400 Myr ago prior to the evolution of leaves and roots in vascular plants [1,2]. As representatives of the earliest and still-surviving vascular plant lineage, the lycophytes are an important group of plants for providing insights into the early evolution of land plants
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