Proteomic analysis of differential responses to norflurazon herbicide in the model green alga Chlamydomonas reinhardtii

Norflurazon is a widely utilized pesticide in agriculture for weed management. The mechanism of action involves the inhibition of an initial step in carotenoid synthesis. This inhibition results in the instability of the photosynthetic machinery and subsequent cell bleaching. Microalgae have attracted significant interest for the production of valuable products. Nonetheless, the mass cultivation of microalgae continues to encounter many challenges that result in high production costs. A potential issue in photobioreactor and open pond cultivation is contamination by other microalgae, which can destroy the mass culture entirely. Strains exhibiting greater resistance to specific chemicals may be beneficial in reducing contamination from other algae. Furthermore, integrating microalgal production with phycoremediation constitutes a sustainable approach to the circular economy. Many norflurazon-resistant microalgae strains have been developed, including the model unicellular green microalga Chlamydomonas reinhardtii. In previous studies, mutant and transgenic strains resistant to high concentrations of norflurazon have been generated to study herbicide tolerance in Chlamydomonas reinhardtii. Nonetheless, the application of genetically engineered organisms should remain cautious. Moreover, mutant strains generated through conventional methods were created using very high chemical concentrations. The effects of introducing such strains on the composition of organisms in the environment remain a concern. This study investigated the feasibility of utilizing natural isolates of this alga for mass production in the presence of norflurazon. Twenty isolates of this alga were evaluated for tolerance to norflurazon. The two most tolerant isolates demonstrated the ability to withstand 5-10 µM of norflurazon, a concentration previously employed to select mutants and transformants resistant to norflurazon. Physiological and proteomic data revealed an enhancement of photosynthesis and photoprotection processes as the primary mechanism for norflurazon tolerance in one isolate, whereas another isolate demonstrated a reduction in protein synthesis, photosynthesis, and cell motility.