Under stress-promoting conditions unicellular algae can undergo programmed cell death (PCD), but the mechanisms are poorly understood. Yordanova et al. expose Chlamydomonas reinhardtii to the G-protein activator mastoparan (MP) and find that cells express several features of necrosis and vacuolar cell death, accompanied by nuclear condensation and DNA fragmentation. Depending on the physiological state of the cells and their sensitivity to MP, a portion of cells undergo early PCD through a process not mediated by capase, whereas other cells die at a slower pace that involves capase-like pathways. The findings thus reveal novel elements of the cell death process in algae and suggest that algal PCD may take different forms and proceed through different pathways.