Does ethylene mediate the autochemotropic and rheotropic responses in Phycomyces?

Area of Science:

• Mycology
• Plant Physiology
• Biophysics

Background:

• The sporangiophore (spph) of Phycomyces blakesleeanus exhibits complex growth responses to environmental stimuli.
• Autochemotropism (avoidance response) and rheotropism (wind response) are key behaviors influencing sporangiophore development and spore dispersal.

Purpose of the Study:

• To investigate the potential role of ethylene in mediating autochemotropism and rheotropism in Phycomyces blakesleeanus sporangiophores.
• To determine if ethylene produced by the fungus is involved in these directional growth responses.

Main Methods:

• Testing avoidance response by placing a barrier near the growing zone of the sporangiophore.
• Assessing the effect of an ethylene oxidant (Purafil) on the avoidance response.
• Evaluating wind response by exposing sporangiophores to laminar air flow, with and without added ethylene.

Main Results:

• The sporangiophore demonstrated a clear avoidance response to a physical barrier, with a lag time of 2-4 minutes.
• Ethylene oxidation did not alter the avoidance response, indicating ethylene is not involved.
• The sporangiophore exhibited positive rheotropism, growing into the wind, a response unaffected by exogenous ethylene application.

Conclusions:

• Ethylene produced by Phycomyces blakesleeanus does not mediate autochemotropism or rheotropism.
• These directional growth responses in Phycomyces sporangiophores are likely regulated by other signaling pathways.