Inheritance of four-membrane-bound structures in the "apicoplast-minus"

Most apicomplexan parasites contain a plastid-derived organelle called the apicoplast, which originated through secondary endosymbiosis. As a result of this evolutionary trajectory, the non-photosynthetic apicoplast is surrounded by four membranes and contains many bacterial-like, druggable targets. It is widely accepted that asexual malaria parasites ( IMPORTANCE: The plant-like organelle named apicoplast is essential for malaria parasites and is a major antimalarial drug target. For more than a decade, scientists have believed that malaria parasites in the blood stages could dispense with the apicoplast if they were supplied with a critical metabolite made by the organelle, leading to the idea of "apicoplast-minus" parasites. Our results challenge this long-standing view. We find that even when the apicoplast is disrupted, the organelle remains in a highly reduced form. This apicoplast-derived organelle is inherited as parasites continue their life cycles, suggesting that it contains essential functions even when the organelle is disrupted. Our data reveal an unexpected level of complexity in apicoplast biology and open new doors for future identification of essential apicoplast-derived pathways that cannot be easily bypassed.