Cytokinin-induced cell cycle regulates MET1 activity during shoot regeneration ($)

The capacity of plants to regenerate new shoots from differentiated tissue – a process called de novo shoot regeneration – confers plasticity to plant development and has also important agricultural applications. Previous studies revealed that DNA METHYLTRANSFERASE1 (MET1) inhibits shoot regeneration through the repression of the shoot initiation-regulator WUSCHEL (WUS). However, upstream regulators of MET1 expression are unknown. Using a combination of genetics, confocal microscopy and molecular biology in Arabidopsis, Liu et al. reveal that MET1 expression is spatially dynamic during shoot regeneration and fine-tunes WUS expression through methylation of its promoter region. Moreover, MET1 expression is enhanced by the cell cycle regulator E2F as well as by the CYCD3 cyclin in a cytokinin-dependent fashion. Altogether, the authors suggest a model where WUS expression is tightly controlled by the local balance between the repressing CK-CYCD3-E2F-MET1 module and the activating cytokinin response factors. These findings reveal a direct epigenetic control of plant regeneration regulated by external signals including phytohormones. (Summary by Matthias Beniot) New Phytol. 10.1111/nph.14814/full