# Epidermal Cell Dynamics Regulates Rice Lamina Joint Morphogenesis and Leaf Angle Formation through OsZHD1 and OsZHD2 Regulation

## TL;DR

This study shows how epidermal cell dynamics in rice lamina joints influence leaf angle and plant architecture through the genes OsZHD1 and OsZHD2.

## Contribution

A live-imaging system reveals that asymmetric epidermal cell behavior, regulated by OsZHD1 and OsZHD2, controls leaf angle formation in rice.

## Key findings

- Asymmetric elongation and division of epidermal cells at the lamina joint edges drive leaf angle formation.
- Mutations in OsZHD1 and OsZHD2 disrupt epidermal cell growth patterns, reducing leaf angle.
- Epidermis-specific OsZHD1 restoration rescues the leaf angle phenotype, confirming its role in morphogenesis.

## Abstract

The lamina joint is a critical determinant of leaf angle and crop architecture. While epidermal cells play a fundamental role in organ morphogenesis, influencing the overall shape and function of plants, their impact on lamina joint morphology has been largely overlooked. A live‐imaging system for the rice lamina joint epidermis is established in this study, enabling precise tracking of cellular dynamics during leaf angle formation. It is found that asymmetric elongation between the lateral and medial edges, determined by spatial differences in the longitudinal elongation and number of epidermal cells, is a key factor in leaf angle formation. Mutations in the homeobox genes OsZHD1 and OsZHD2 disrupt the growth patterns of lamina joint epidermal cells, resulting in a decreased leaf angle. Epidermis‐specific restoration of OsZHD1 expression rescues the reduced leaf angle phenotype of oszhd1 oszhd2, confirming the pivotal role of epidermal development in lamina joint morphogenesis. Transcriptomic analysis indicates that OsZHD1 and OsZHD2 regulate auxin activity, which modulates leaf angle by restricting lamina joint epidermal growth. This study underscores the significance of epidermal cells in shaping the lamina joint and elucidates the critical role of OsZHD1 and OsZHD2 in regulating epidermal cell behavior and leaf angle formation.

The lamina joint determines leaf angle and plant architecture. Xu et al. establish a live‐imaging system for the rice lamina joint and reveal that asymmetric epidermal cell elongation and division between the lateral and medial edges drive leaf angle formation. OsZHD1 and OsZHD2 coordinate this process by modulating auxin activity and BR signaling.