Programmed cell death in Chlamydomonas reinhardtii induced by cyanobacterial volatile α-ionone

Abstract:

[Objective] Allelopathic effects of cyanobacterial volatile organic compounds (VOCs) on other algae promote cyanobacteria becoming the dominant species in eutrophicated waters. The aim of the present study is to uncover the allelopathic lethal mechanism of cyanobacterial VOCs by using α-ionone.[Methods] In the treatment with α-ionone, the cell growth of Chlamydomonas reinhardtii was investigated, and the photosynthetic abilities, caspase-like activities and DNA ladders were investigated at lethal concentration.[Results] When C. reinhardtii cells were treated with α-ionone at 0.05 and 0.1 mmol/L, the cell growth was significantly inhibited, and 38.3% of the cells were killed by 0.1 mmol/L α-ionone. However, all the cells were killed by 0.2 mmol/L α-ionone. During the cell death, the photosynthetic pigments gradually degraded with prolonging the treatment time, and Fv/Fm gradually declined and even disappeared, indicating that the cell death is not a necrosis. Meanwhile, the activities of caspase-9-like and caspase-3-like increased remarkably. In the treatment with 0.2 mmol/L α-ionone for 1 h, DNA showed ladders and then gradually degraded to the fragments of 100-250 bp.[Conclusion] This suggests that cyanobacterial VOCs play the allelopathic role by inducing programmed cell death.

Key words:cyanobacteria;Chlamydomonas reinhardtii;α-ionone;programmed cell death;allelopathic mechanism