DOI: 10.5061/dryad.ht76hdrdr
title: Two leaves that cannot die: the genome sequence of Welwitschia mirabilis reveals its unique biology and evolutionary history

description: Welwitschia mirabilis (hereafter Welwitschia), the sole species in
 Welwitschiales, belongs to gnetophytes, an ancient, enigmatic gymnosperm
 lineage. It is a strikingly bizarre plant with distinctive morphology of
 just two large ever-elongating leaves and is remarkable in being able to
 survive extreme environmental stresses of the Namibian and Angolan
 deserts. Here, we provide a chromosome-level assembly of its genome (6.8
 Gb/1C) and extensive methylome and transcriptome data to reveal the
 genetics underpinning its intriguing biology. The Welwitschia genome has
 been shaped by a lineage-specific ancient whole genome duplication ~ 86
 million years ago, and more recently (within 10 million years) by bursts
 of retrotransposon activity. In addition, high levels of cytosine
 methylation, extremely so for CHH motifs, are associated with
 retrotransposons, whilst their long-term deamination has resulted in an
 exceptionally GC-poor genome. High levels of methylation are likely to be
 responses to maintain genomic integrity in the face of stress-induced
 retroelement mobility while reduced GC content will confer a genomic
 advantage under nutrient limitation. Changes in the copy number and/or
 expression of key gene families and specific transcription factors (e.g.
 R2R3MYB, SAUR) controlling cell growth, differentiation and metabolism
 underpin the plant’s extreme longevity under increasing temperature,
 nutrient and water stress. The Welwitschia chromosome level assembly here,
 along with a new high-quality assembly for Gnetum montanum, enhances our
 understanding of genome evolution in gnetophytes. It also provides
 critical new insights into the extraordinary development of Welwitschia’s
 ever-growing leaves, enabling its survival in such hostile conditions.
description:     <strong>G.montanum.final.fasta.gz</strong>:
 Assemble genome file of Gnetum montanum (hic improve version)<br>   
  <strong>G.montanum.final.gff.gz</strong>: Annotation gff file
 of Gnetum montanum (hic improve version)<br>   
  <strong>G.montanum.final.pep.gz</strong>: Protein file of
 Gnetum montanum (hic improve version)<br>   
  <strong>G.montanum.final.cds.gz</strong>: Coding sequence
 file of Gnetum montanum (hic improve version)<br>   
  <strong>W.mirabilis.final.fasta.gz</strong>: Assemble genome
 file of Welwitschia mirabilis<br>   
  <strong>W.mirabilis.final.new.gff.gz</strong>: Annotation gff
 file of Welwitschia mirabilis<br>   
  <strong>W.mirabilis.final.new.pep.gz</strong>: Protein file
 of Welwitschia mirabilis<br>   
  <strong>W.mirabilis.final.new.cds.gz</strong>: Coding
 sequence file of Welwitschia mirabilis<br>   
  <strong>W.mirabilis.final.all.repeat.gff.gz</strong>: Repeat
 Annotation gff file of Welwitschia mirabilis<br>   
  <strong>W.mirabilis.final.rpkm.xls.gz</strong>: Rpkm file of
 Welwitschia mirabilis's protein<br>   
  <strong>W.mirabilis.final.trembl.xls.gz</strong>: Function
 annotation by Trembl<br>   
  <strong>W.mirabilis.final.swissprot.xls.gz</strong>: Function
 annotation by Swissprot<br>   
  <strong>W.mirabilis.final.kegg.xls.gz</strong>: Function
 annotation by Kegg<br>   
  <strong>W.mirabilis.final.go.xls.gz</strong>: Function
 annotation by GO<br>   
  <strong>W.mirabilis.final.ipr.xml.gz</strong>: Function
 annotation by InterProScan