PUCHI controls MYB94 and MYB96 to form the root cap cuticle of developing lateral roots.

Abstract

Lateral root organogenesis underlies root branching and plays a key role in plant root system architecture. While the transcriptional and hormonal control of lateral root development has been extensively studied over the past decades, an increasing number of studies highlight the importance of specific metabolic pathways contributing to the lateral root regulatory network. The AP2/ERF transcription factor PUCHI has recently been shown to orchestrate the induction of very-long-chain fatty acid biosynthesis in developing lateral root primordia. In parallel, a root cap cuticle, reminiscent of the very-long-chain fatty acid-rich cuticle covering the emerging primary root, was shown to cover developing lateral root primordia and facilitate their emergence. Here, we demonstrate that PUCHI plays an essential role in lateral root cap cuticle formation. We identified the transcription factors MYB94 and MYB96 as key intermediates in this PUCHI-dependent, cuticle regulatory network. Similar to PUCHI, MYB94 and MYB96 induce the expression of a set of very-long-chain fatty acid- and cutin-related genes in lateral root primordia. The loss of function of either PUCHI or that of MYB94 and MYB96 compromises lateral root cuticle deposition, delays lateral root emergence, and alters the expression pattern of lateral root meristematic genes. These results shed light on a PUCHI- and MYB94 and MYB96-dependent regulatory network controlling the lateral root cap cuticle formation and influencing lateral root primordium development and emergence.