Genetic variation for sensitivity to a thyme monoterpene in associated plant species

Recent studies have shown that plant allelochemicals can have profound effects on the performance of associated species, such that plants with a history of co-existence with “chemical neighbour” plants perform better in their presence compared to naïve plants. This has cast new light on the complexity of plant–plant interactions and plant communities and has led to debates on whether plant communities are more co-evolved than traditionally thought. In order to determine whether plants may indeed evolve in response to other plants’ allelochemicals it is crucial to determine the presence of genetic variation for performance under the influence of specific allelochemicals and show that natural selection indeed operates on this variation. We studied the effect of the monoterpene carvacrol—a dominant compound in the essential oil of Thymus pulegioides—on three associated plant species originating from sites where thyme is either present or absent. We found the presence of genetic variation in both naïve and experienced populations for performance under the influence of the allelochemical but the response varied among naïve and experienced plant. Plants from experienced populations performed better than naïve plants on carvacrol soil and contained significantly more seed families with an adaptive response to carvacrol than naïve populations. This suggests that the presence of T. pulegioides can act as a selective agent on associated species, by favouring genotypes which perform best in the presence of its allelochemicals. The response to the thyme allelochemical varied from negative to neutral to positive among the species. The different responses within a species suggest that plant–plant interactions can evolve; this has implications for community dynamics and stability

Enantiomeric Natural Products: Occurrence and Biogenesis

In nature, chiral natural products are usually produced in optically pure form—however, occasionally both enantiomers are formed. These enantiomeric natural products can arise from a single species or from different genera and/or species. Extensive research has been carried out over the years in an attempt to understand the biogenesis of naturally occurring enantiomers; however, many fascinating puzzles and stereochemical anomalies still remain. Two sides to the story : The formation of enantiomerically opposite natural products by nature is known, although rare (see examples). To date, many puzzles and stereochemical anomalies remain regarding the biogenesis of these unique natural products, despite the substantial body of research that has been carried out over the years in an attempt to understand the biogenesis of enantiomeric metabolites.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92098/1/4802_ftp.pd

Enantiomere Naturstoffe: Vorkommen und Biogenese

In der Natur werden chirale Substanzen meist in enantiomerenreiner Form synthetisiert – manchmal entstehen aber auch beide Enantiomere. Solche enantiomeren Naturstoffe können von einer Art oder von verschiedenen Gattungen und/oder Arten gebildet werden. Intensive Forschungen wurden über viele Jahre durchgeführt, um die Biogenese natürlich vorkommender Enantiomere zu verstehen, doch viele faszinierende Rätsel und stereochemische Anomalien sind nach wie vor ungelöst. Bild und Spiegelbild in der Natur: Die Bildung von natürlich vorkommenden Enantiomerenpaaren ist bekannt, wenn auch selten (siehe Beispiel). Bis heute sind noch viele Rätsel und stereochemische Anomalien bei der Biogenese dieser einmaligen Naturstoffe ungelöst, auch wenn im Laufe der Jahre viel Arbeit investiert worden ist, um die Entstehung enantiomerer Metaboliten zu verstehen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91315/1/4886_ftp.pd