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Keywords:

  • Flaveria;
  • Asteraceae;
  • C4 photosynthesis;
  • evolution;
  • glycine cleavage system;
  • H-protein;
  • photorespiration;
  • phylogeny

ABSTRACT

Sequence comparisons have shown that nucleotide sequences of the H-protein, a component of the glycine cleavage system, are only moderately conserved and can be used as molecular markers for intrageneric phylogenetic studies. We have analysed the respective cDNA sequences from 12 species of Flaveria, and a more limited set of gdcsH upstream regions. These data are discussed with respect to a phylogenetic reconstruction of Flaveria, a small genus which includes species of different photo-synthetic types, namely C3, C3-C4, C4-like and C4. Our analysis essentially supports an earlier hypothesis, based on morphological and eco-geographical data, of the evolution of Flaveria (Powell 1978). This close agreement shows the usefulness of H-protein nucleotide sequences at a low taxonomic level. Our analysis independently confirms that C4 photosynthesis has evolved two times in different lineages of Flaveria. Most remarkably, the C4 taxa of Flaveria appear as derived relative to the C3-C4 intermediate taxa, i.e. they probably have common direct predecessors. This is the first direct evidence for a phylo-genetically intermediate position of C3-C4 intermediate photosynthesis. Our data also confirm the antiquity of C3 photosynthesis in Flaveria but suggest that the collection of F.pringlei used in our experiments, although clearly of C3 photosynthetic metabolism, possibly originated from hybridization with a more advanced taxon.