Plant casein kinases phosphorylate and destabilize a cyclin-dependent kinase inhibitor to promote cell division

Cell cycle is one of the most fundamentally conserved biological processes of plants and mammals. Casein kinasels (CK1s) are critical for cell proliferation in mammalian cells; however, how CK1s coordinate cell division in plants remains unknown. Through genetic and biochemical studies, here we demonstrated that plant CK1, Arabidopsis (Arabidopsis thaliana) EL1-like (AELs), regulate cell cycle/division by modulating the stability and inhibitory effects of Kip-related protein6 (KRP6) through phosphorylation. Cytological analysis showed that AELs deficiency results in suppressed cell-cycle progression mainly due to the decreased DNA replication rate at S phase and increased period of G2 phase. AELs interact with and phosphorylate KRP6 at serines 75 and 109 to stimulate KRP6's interaction with E3 ligases, thus facilitating the KRP6 degradation through the proteasome. These results demonstrate the crucial roles of CK1s/AELs in regulating cell division through modulating cell-cycle rates and elucidate how CK1s/AELs regulate cell division by destabilizing the stability of cyclin-dependent kinase inhibitor KRP6 through phosphorylation, providing insights into the plant cell-cycle regulation through CK1s-mediated posttranslational modification.

Automated summary

This study demonstrates the crucial role of plant CK1/AELs in regulating cell division by modulating the stability and inhibitory effects of KRP6, affecting DNA replication rate and cell-cycle progression. The interaction between AELs and KRP6, along with the phosphorylation at specific serine residues, promotes KRP6 degradation through the proteasome pathway, providing insights into plant cell-cycle regulation through CK1s-mediated posttranslational modification.