Toxicity of the dithiocarbamate fungicide mancozeb to the nontarget soil nematode, Caenorhabditis elegans

Area of Science:

• Environmental toxicology
• Nematode biology
• Biochemical stress responses

Background:

• Dithiocarbamate fungicides like Mancozeb and Maneb are widely used agricultural chemicals.
• Previous studies indicated Mancozeb induces heat-shock response in C. elegans, while Maneb shows weaker effects.
• Understanding fungicide toxicity in non-target organisms is crucial for environmental risk assessment.

Purpose of the Study:

• To investigate the time-dependent effects of Mancozeb and Maneb on C. elegans.
• To assess the toxicity of Mancozeb's metabolite, ethylenethiourea (ETU).
• To compare the sensitivity of reporter gene induction and larval growth inhibition as toxicological endpoints.

Main Methods:

• Utilized a transgenic C. elegans strain (PC72) with a lacZ reporter under a heat-shock promoter (hsp16).
• Exposed nematodes to Mancozeb, Maneb, and ETU for varying durations.
• Measured lacZ reporter expression, larval growth, and protein profiles using two-dimensional electrophoresis.

Main Results:

• Mancozeb-induced reporter expression increased significantly with prolonged exposure (overnight vs. hours).
• Ethylenethiourea (ETU) showed minimal toxicity to C. elegans.
• Mancozeb, but not ETU, inhibited larval growth; this endpoint was not more sensitive than reporter induction.
• Both fungicides altered protein profiles, with Mancozeb uniquely inducing novel proteins.

Conclusions:

• Mancozeb's toxicity and heat-shock response in C. elegans are time-dependent, likely due to slow uptake or metabolism.
• Mancozeb poses a greater toxicological risk to C. elegans than Maneb or its metabolite ETU.
• Reporter gene induction serves as a sensitive toxicological endpoint for assessing fungicide effects in C. elegans.