A distributive germline restricts the spread of new mutations

Abstract

Genetic bottlenecks in the germline can amplify the impact of mutations, increasing the likelihood that new mutations are transmitted to multiple offspring. Here, we evaluate the timing and consequences of bottlenecks leading to maize pollen. By tracking transposon-induced mutations across tissues, we find that pollen derives from multiple early embryonic cell lineages, maintained by radial symmetries throughout development. In controlled crosses, offspring from bulk pollen or apical branches rarely share mutations, whereas lateral branches sample fewer lineages and produce offspring with a 6.2-fold increase in mutation sharing. Thus, the persistence of multiple, early-diverged cell lineages into the germline reduces mutation recurrence without altering the underlying mutation rate. Similar principles may apply in animals, where diverse mechanisms ensure that multiple cell lineages contribute to the germline.