Splitting the difference on peroxisomes

The question of whether cells manufacture new peroxisomes from scratch or cleave existing organelles has divided researchers. On page 399, Motley and Hettema show that yeast opt for the second mechanism, only turning to synthesis if they run out of the organelles.

Packed with enzymes, peroxisomes are essential for defusing cellular toxins—a shortage of the organelles triggers the lethal disorder Zellweger syndrome. Before a cell divides, it duplicates its stock of peroxisomes, half of which it then parcels out to its daughter cell. But research on how cells fashion more peroxisomes has produced contradictory results. Some work suggests that new structures bud from the endoplasmic reticulum. Other findings suggest that new peroxisomes form when existing ones split. A third explanation is...