Cyclin-dependent kinase inhibitors ensure formation of one functional megaspore per ovule (PLOS Genet)

Usually the female germline starts with one MMC (megaspore mother cell) per ovule that becomes four megaspores through the process of meiosis. Out of these four, only one survives to produce a functional megaspore (FM); the other three undergo a degeneration process. The FM forms the embryo sac. In this study, Cao et al. took the advantage of ICK/KRPs (interactor/inhibitor of cyclin-dependent kinase /Kip-related proteins) mutants to understand the selective process of embryo sac formation. In the septuple mutant in which all seven ICK/KRP genes are inactivated, more than one MMC, FM and embryo sac forms. Additionally, the authors demonstrated that ICK4 is only expressed in the degenerated megaspores, not in FM. This work showed that selective embryo sac formation and megaspore degeneration are mediated by the redundant function of ICK/KRPs. (Summary by Arif Ashraf) PLOS Genetics: 10.1371/journal.pgen.1007230