Evaluation Summary:
Mitochondria have their own DNA, which is much more likely to gain mutation (due to error-prone DNA polymerase). It is widely appreciated that there are quality control mechanisms such that functional mitochondria are passed from one generation to the next. The proposed mechanisms include a passive mechanism (generation of the bottleneck) as well as an active mechanism (selective removal of non-functional mitochondria), but the processes are not fully understood. This manuscript presents fascinating observations as to how C. elegans germline may remove mitochondria by creating bottlenecks as well as selectively removing non-functional mitochondria. Building upon the authors' previous finding that the C. elegans primordial germ cells (PGCs) shed much of cytoplasm during embryogenesis through 'cannibalism', they now describe that a bulk of mitochondria are removed from PGCs through this process.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewer #1 agreed to share their name with the authors.)