GH3‐mediated auxin inactivation attenuates multiple stages of lateral root development

Abstract

Summary Lateral root (LR) positioning and development rely on the dynamic interplay between auxin production, transport but also inactivation. Nonetheless, how the latter affects LR organogenesis remains largely uninvestigated. Here, we systematically analyze the impact of the major auxin inactivation pathway defined by GRETCHEN HAGEN3‐type (GH3) auxin conjugating enzymes and DIOXYGENASE FOR AUXIN OXIDATION1 (DAO1) in all stages of LR development using reporters, genetics and inhibitors in Arabidopsis thaliana. Our data demonstrate that the gh3.1/2/3/4/5/6 hextuple (gh3hex) mutants display a higher LR density due to increased LR initiation and faster LR developmental progression, acting epistatically over dao1‐1. Grafting and local inhibitor applications reveal that root and shoot GH3 activities control LR formation. The faster LR development in gh3hex is associated with GH3 expression domains in and around developing LRs. The increase in LR initiation is associated with accelerated auxin response oscillations coinciding with increases in apical meristem size and LR cap cell death rates. Our research reveals how GH3‐mediated auxin inactivation attenuates LR development. Local GH3 expression in LR primordia attenuates development and emergence, whereas GH3 effects on pre‐initiation stages are indirect, by modulating meristem activities that in turn coordinate root growth with LR spacing.

SbPIP2Mediated Improvements in Plant Resilience: Physiological and Molecular Insights into Abiotic Stress Response

“…This observation supports the notion of elevated auxin levels facilitating root growth in transgenic plants as compared to their wildtype counterparts under saline conditions (data not shown). Previous studies in Arabidopsis showed that GH3 protein act as a negative regulator in lateral root development and promoting primary root growth (Wang et al, 2023). Auxin-responsive GH3-like protein 5 under salinity stress, and both Indole-3-acetic acid-amido synthetase GH3.10 and GH3.11 under drought conditions were increased in transgenic plants supporting significantly higher primary root length in transgenic plant seedling (data not shown).…”

Comparative Transcriptome Analysis Reveals Inhibitory Roles of Strigolactone in Axillary Bud Outgrowth in Ratoon Rice

“…The reduced expression of OsYUCC5 confirmed local auxin biosynthesis in buds, which is necessary as an auxin source. The GRETCHEN HAGEN 3 (GH3) acyl acid amido synthetase family, pivotal in conjugating IAA with amino acids, has been proposed as part of an important auxin attenuation mechanism, based on its auxin-conjugating enzymatic activity and gain-of-function phenotypes [ 33 , 34 ]. Here, we found that the relative expressions of OsGH3.8 and OsGH3.6 in the axillary bud outgrowth were significantly induced after GR24 treatment ( Figure 6 A), which implies that SL may affect the IAA content in ratoon rice by promoting IAA metabolism.…”

The Roles of GRETCHEN HAGEN3 (GH3)-Dependent Auxin Conjugation in the Regulation of Plant Development and Stress Adaptation

“…Previous studies found that the exogenous addition of IAA-aa and IAA both rapidly increased content-free IAA levels and exhibited similar high growth factor phenotypes, suggesting that IAA-aa is a storage form of IAA [ 103 ]. Subsequent studies found that these IAA-aa, IAA-Leu, and IAA-Ala could be reversibly converted to free IAA by the action of the hydrolases, IAA-LEUCINE RESIS TANT1 (ILR1), ILR1-LIKE proteins (ILLs), and IAA-ALANINE RESISTANT3 (IAR3) [ 5 , 104 , 105 ].…”