Bryological and Lichenological Section/ABLS
Huizenga, Cassandra A. , Wickett, Norman J. , Budke, Jessica M. , Parry, Lauren E. , Goffinet, Bernard .
Evolution of two chloroplast-encoded sulfate import genes, cysA and cysT, in liverworts.
The plastid genes cysA and cysT encode proteins whose probable function is involved with the import of sulfate into the plastid, where it is incorporated into cysteine and methionine residues. Within embryophytes, these two genes are not universally present. Both fully sequenced plastid genomes of liverworts, the likely sister group to all other embryophytes, include cysA and cysT. However, in Aneura mirabilis, a non-photosynthetic liverwort, these genes are pseudogenes characterized by short deletions that disrupt the reading frame. The plastid genome of the hornwort Anthoceros formosae includes both genes, whereas the plastid genome of the moss Physcomitrella patens does not. All sequenced tracheophyte plastid genomes lack these genes. Surveys of the family to which A. mirabilis belongs (Aneuraceae) revealed that both cysA and cysT are also pseudogenes in some photosynthetic members of the family, and in these cases present greater gene decay than in A. mirabilis. We present here a survey of the major lineages of the backbone phylogeney of liverworts for the presence of these two genes. Both cysA and cysT appear to have been lost multiple times throughout the evolution of liverworts. Of the six major clades of liverworts, only the complex thalloids and Leafy I appear to be characterized by a single state for cysA; it is present in all complex thalloids surveyed and absent in all accessions surveyed from the Leafy I clade. We discuss here the phylogenetic distribution of cysA and cysT and whether their distributions are congruent, we reconstruct the ancestral condition for liverworts, and discuss the possible phylogenetic utility of the cysA pseudogene.
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1 - University of Connecticut, Ecology and Evolutionary Biology, 75 N. Eagleville Rd., Storrs, CT, 06269-3043, USA
2 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM