Developmental control of endocycles and cell growth in plants

Timely progression of the mitotic cell cycle is central for growth and development of plant organs. Many cell types in plants also enter an alternative cell cycle called the endoreduplication cycle or endocycle in which cells increase their ploidy through repeated rounds of chromosomal replication without cell divisions. The transition from the mitotic cycle into the endocycle often coincides with the initiation of cell expansion and cell differentiation, and strong correlations between final ploidy level and cell size have been reported in many plant species. Recent studies have begun to unveil how developmental signals modulate entry and exit of the endocycle through both transcriptional and post-transcriptional mechanisms. An increase in ploidy by endocycles is not an ultimate determinant of plant cell size and it is likely that it sets the maximum capacity for future cellular growth.

Research highlights▶ Auxin regulates the transition from the mitotic cycle to the endocycle, and this involves the PLETHORA and HPY2 SUMO E3 ligase genes. ▶ CCS52 is an evolutionarily conserved regulator of endocycle onset in higher plants that promotes the proteolysis of cell cycle proteins. ▶ Plant cells grow in both ploidy-dependent and ploidy-independent manners, and transcription factors regulating each type of growth have been identified.