Root branching under high salinity requires auxin-independent modulation of LATERAL ORGAN BOUNDARY DOMAIN 16 function
Yanxia Zhang, Yiyun Li, Thijs de Zeeuw, Kilian Duijts, Dorota Kawa, Jasper Lamers, Kristina S Munzert, Hongfei Li, Yutao Zou, Anne Meyer, Jinxuan Yan, Francel Verstappen, Yixuan Wang, Tom Gijsberts, Jielin Wang, Nora Gigli‐Bisceglia, Timo Engelsdorf, Aalt D. J. van Dijk, Christa Testerink
Abstract
Salinity stress constrains lateral root (LR) growth and severely affects plant growth. Auxin signaling regulates LR formation, but the molecular mechanism by which salinity affects root auxin signaling and whether salt induces other pathways that regulate LR development remains unknown. In Arabidopsis thaliana, the auxin-regulated transcription factor LATERAL ORGAN BOUNDARY DOMAIN 16 (LBD16) is an essential player in LR development under control conditions. Here, we show that under high-salt conditions, an alternative pathway regulates LBD16 expression. Salt represses auxin signaling but, in parallel, activates ZINC FINGER OF ARABIDOPSIS THALIANA 6 (ZAT6), a transcriptional activator of LBD16. ZAT6 activates LBD16 expression, thus contributing to downstream cell wall remodeling and promoting LR development under high-salt conditions. Our study thus shows that the integration of auxin-dependent repressive and salt-activated auxin-independent pathways converging on LBD16 modulates root branching under high-salt conditions.