Molecular response of an invasive weed to different competitive conditions.

Competition is a major determinant of plant community structure consisting of both species-specific and general interactions, either of which may influence competitive competency and plant abundance and size. In certain cases, competitive competency could arise from altered gene expression and plant function when an individual is confronted with new competitors. We explored competition at the molecular level by hybridizing transcripts from Centaurea maculosa (spotted knapweed), one of North America's most invasive exotic plant species, to an Arabidopsis microarray chip. Centaurea was grown in competition with Festuca idahoensis (Idaho fescue), a native grass species that generally has weak competitive effects against Centaurea; Gaillardia aristata (Indian blanketflower), a native herbaceous species that tends to be a much stronger competitor against Centaurea; or alone (control). The expression of some genes was found to be relatively uninfluenced by the type of plant neighbor, whereas other patterns of gene expression appeared to be more neighbor specific. To our knowledge, these results are the first to identify genes in an invasive plant that are induced or repressed by plant neighbors and provide a new avenue of insight into the molecular aspects of plant competitive ability. Keywords: treated vs.untreated Files; chip 618 (12-7-05) and chip 623 (1-20-06) are replicates. One channel is root cDNA from Centaurea maculosa grown in isolation and the other channel is root cDNA from Centaurea maculosa grown with a strong competitor, Gaillardia aristata. For each chip, RNA extractions on unique biological samples were performed. Files; chip 720 (2-23-06) and chip 723 (3-17-06) are replicates. One channel is root cDNA from Centaurea maculosa grown in isolation and the other channel is root cDNA from Centaurea maculosa grown with a weak competitor, Festuca idahoensis. For each chip, RNA extractions on unique biological samples were performed.