Root-specific photoreception directs early root development by HY5-regulated ROS balance.

Abstract

Root development is tightly controlled by light, and the response is thought to depend on signal transmission from the shoot. Here, we show that the root apical meristem perceives light independently from aboveground organs to activate the light-regulated transcription factor <i>ELONGATED HYPOCOTYL5</i> (<i>HY5</i>). The ROS balance between H₂O₂ and superoxide anion in the root is disturbed under darkness with increased H₂O₂. We demonstrate that root-derived HY5 directly activates <i>PER6</i> expression to eliminate H₂O₂. Moreover, HY5 directly represses <i>UPBEAT1</i>, a known inhibitor of peroxidases, to release the expression of <i>PERs</i>, partially contributing to the light control of ROS balance in the root. Our results reveal an unexpected ability in roots with specific photoreception and provide a mechanistic framework for the HY5-mediated interaction between light and ROS signaling in early root development.