Abstract Detail

After the book - Progress in parasitic plant research since Kuijt's Biology of Parasitic Flowering Plants (1969)

Bennett, Jonathan [1], Mathews, Sarah [1].

Phytochrome evolution in Orobanchaceae.

The evolution of complete or partial heterotrophy in plants may involve the evolution of new morphological features such as haustoria. There may also be reduced selective pressure for the maintenance of features associated with photosynthesis. Some developmental processes mediated by phytochrome photoreceptors are altered in parasitic plants. These include leaf and chloroplast development, the expansion of cotyledons and the expression of photosynthetic genes. Orobanchaceae contains holoparasitic species, which produce highly reduced leaves, and remain non-photosynthetic throughout their life cycle, and hemiparasitic species, which produce leaves and photosynthesize for some or all of their life cycle. The family thus offers a system in which to investigate how the functions of phytochromes might be altered in parasitic plants. We have used DNA sequences of PHYA, the gene encoding one of the four phytochromes that are widely distributed in angiosperms, to infer a well-supported phylogeny for the family. Our sampling includes for the first time representatives of Nesogenes and Xylocalyx from Africa, which are nested within Orobanchaceae. The robust gene phylogeny suggests that at least some hemiparasites and holoparasites have two copies of PHYA and that some PHYA genes harbor novel introns. We also have found evidence that PHYA sequences are evolving under relaxed constraints and we are investigating patterns of molecular evolution in more detail to determine whether selective pressures change along branches to major clades or whether they might be closely correlated with shifts in habit.

1 - Harvard University, Arnold Arboretum, 22 Divinity Avenue, Cambridge, Massachusetts, 02138, USA

Keywords:
phytochrome
Orobanchaceae
molecular evolution.

Presentation Type: Symposium
Session: 4-5
Location: Ballroom 2 (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 10:15 AM
Abstract ID:238