Plastid genome structure and loss of photosynthetic ability in the parasitic genus Cuscuta
Meredith J. W. Revill, Susan Stanley and Julian M. Hibberd*
Department of Plant Sciences, University of Cambridge, Downing St, Cambridge CB2 3EA, UK
* To whom correspondence should be addressed. Fax: +44 (0)1223 333953. E-mail: firstname.lastname@example.org
Received 8 December 2004; Accepted 30 May 2005
The genus Cuscuta (dodder) is composed of parasitic plants, some species of which appear to be losing the ability to photosynthesize. A molecular phylogeny was constructed using 15 species of Cuscuta in order to assess whether changes in photosynthetic ability and alterations in structure of the plastid genome relate to phylogenetic position within the genus. The molecular phylogeny provides evidence for four major clades within Cuscuta. Although DNA blot analysis showed that Cuscuta species have smaller plastid genomes than tobacco, and that plastome size varied significantly even within one Cuscuta clade, dot blot analysis indicated that the dodders possess homologous sequence to 101 genes from the tobacco plastome. Evidence is provided for significant rates of DNA transfer from plastid to nucleus in Cuscuta. Size and structure of Cuscuta plastid genomes, as well as photosynthetic ability, appear to vary independently of position within the phylogeny, thus supporting the hypothesis that within Cuscuta photosynthetic ability and organization of the plastid genome are changing in an unco-ordinated manner.
Key words: Cuscuta, parasitic plants, photosynthesis, phylogeny, plastome
Journal of Experimental Botany 2005 56(419):2477-2486. Published by Oxford University Press [on behalf of the Society for Experimental Biology].