# Natural Variations of ZmRLR1 Mediate the Root Lodging Resistance of Maize by Regulating Root Ascorbate and Auxin Homeostasis

## TL;DR

This study shows that natural variations in the ZmRLR1 gene help maize resist root lodging by controlling root ascorbate and auxin levels.

## Contribution

The paper identifies ZmRLR1 as a novel regulator of root lodging resistance through its dual role in redox balance and clathrin-mediated endocytosis.

## Key findings

- ZmRLR1 overexpression increases root lodging resistance by enhancing root growth and soil anchoring.
- Natural promoter variations in ZmRLR1 correlate with differences in root lodging resistance in maize.
- ZmRLR1 influences auxin distribution and endocytic processes, which are critical for root development.

## Abstract

Root lodging is a major problem limiting crop yield and seed quality. Here, we showed that Root Lodging Resistance 1 (ZmRLR1) is specifically expressed in maize roots. The overexpression of ZmRLR1 increased the rhizosphere soil weight, stem pulling force of the internode 50 cm from the ground, total root length, and root volume. In contrast, the rhizosphere soil weight, stem pulling force of the internode 50 cm from the ground, total root length, and root volume were reduced in the Zmrlr1ems
and Zmrlr1 mutants. Natural variations in the promoter of ZmRLR1 are significantly associated with the root lodging resistance of maize. ZmRLR1 positively regulates the ascorbate (AsA) content in maize roots. We further demonstrated that ZmRLR1 improved the interaction between the ZmAP2 σ subunit and ZmCHC2. The internalization of the endocytic tracer FM4‐64 is substantially reduced in the Zmrlr1ems
and Zmrlr1 mutants, while auxin distribution and ZmPIN1a‐YFP localization are altered in Zmrlr1ems
. The defect in the total root length of Zmrlr1ems
is rescued by the exogenous application of 10 µmol L−1 AsA plus 0.01 µmol L−1 1‐naphthaleneacetic acid. Taken together, these results suggest that ZmRLR1 affects the root lodging resistance of maize by regulating root AsA and auxin homeostasis.

Root lodging severely limits crop yield and quality. We reveal that ZmRLR1, a plasma membrane b‐type cytochrome, regulates lodging resistance in maize through dual roles: modulating intracellular redox balance and functioning as a novel component of clathrin‐mediated endocytosis to influence auxin homeostasis. Moreover, natural variations in the ZmRLR1 promoter affect the root lodging resistance of maize.