Attraction Pheromone of The Benthic Diatom Seminavis robusta: Studies on Structure-Activity Relationships

Area of Science:

• Marine biology
• Chemical ecology
• Diatom reproduction

Background:

• The first marine diatom pheromone, (S,S)-diproline, a diketopiperazine, was recently identified in *Seminavis robusta*.
• Diatom mating involves chemical attraction, but the specificity of pheromone perception is not well understood.
• Typically, pheromone interactions are stereospecific, with high enantioselectivity.

Purpose of the Study:

• To investigate the structure-activity relationship of diketopiperazines in diatom pheromone reception.
• To determine the stereospecificity of pheromone perception in the marine diatom *Seminavis robusta*.
• To identify structural features critical for diatom pheromone activity.

Main Methods:

• A structure-activity relationship study was conducted using nine different diketopiperazines.
• Attraction and interference assays were performed to evaluate bioactivity.
• Enantioselective high-performance liquid chromatography (HPLC) was used to purify stereoisomers for testing.

Main Results:

• The natural pheromone (S,S)-diproline and a pipecolic acid-derived diketopiperazine showed the highest attractivity.
• Hydroxylation of aliphatic rings abolished bioactivity, and diketopiperazines from acyclic amino acids were inactive.
• All tested stereoisomers of active diketopiperazines confirmed that attraction and pheromone perception in this diatom are not stereospecific.

Conclusions:

• Diatom pheromone perception is not stereospecific, as both enantiomers of active diketopiperazines elicit attraction.
• Structural specificity exists, preventing attraction to diketopiperazines derived from acyclic amino acids, thus avoiding misguidance.
• This study provides insights into the molecular basis of chemical communication and mating in marine diatoms.