PIF7 controls leaf cell proliferation through an AN3 substitution repression mechanism
Ejaz Hussain, Andrés Romanowski, Karen Halliday
Abstract
Significance Phytochrome photoreceptors can markedly alter leaf blade growth in response to far-red (FR) rich neighbor shade, yet we have a limited understanding of how this is accomplished. This study identifies ANGUSTIFOLIA3 (AN3) as a central component in phytochrome promotion of leaf cell proliferation and PHYTOCHROME-INTERACTING FACTOR 7 (PIF7) as a potent repressor. AN3 and PIF7 impose opposing regulation on a shared suite of genes through common cis -acting promoter elements. In response to FR light, activated PIF7 blocks AN3 action by evicting and substituting for AN3 at target promoters. This molecular switch module provides a mechanism through which changes in external light quality can dynamically manipulate gene expression, cell division, and leaf size.