The bHLH121-CAT2 module maintains root tip redox homeostasis to confer salt tolerance additively with the SOS pathway in Arabidopsis
- 1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China
Abstract
Soil salinity inhibits plant growth, in part, by restricting the availability of essential mineral nutrients such as iron (Fe). Although Fe deficiency frequently coincides with salt stress in the field, the molecular mechanisms integrating Fe homeostasis with salt tolerance remain largely unknown. Here, we identify the Fe deficiency response regulator bHLH121 as a key coordinator of salt tolerance in Arabidopsis. Loss-of-function mutants of bHLH121 exhibit pronounced hypersensitivity to salt stress, with severely impaired primary root elongation and reduced seedling biomass. Transcriptomic and histochemical analyses reveal that bHLH121 is required to maintain reactive oxygen species (ROS) homeostasis specifically in root tips under salt stress. We further demonstrate that CATALASE 2 (CAT2) is a direct downstream target of bHLH121, and that CAT2 overexpression fully rescues the salt hypersensitivity of the bhlh121 mutant. Importantly, this bHLH121-CAT2 module operates independently of the classical SOS pathway, as sos2 bhlh121 double mutants display additive salt sensitivity. Together, our findings uncover a novel regulatory module in which bHLH121 governs root tip redox homeostasis through CAT2 to confer salt tolerance, providing a direct mechanistic link between the Fe regulatory network and abiotic stress resilience in plants.
Related
- A bHLH121/URI-ANAC017-MAT1/SAM1 regulatory cascade controls iron homeostasis in Arabidopsis.
- Cytokinin-activated DIRIGENT13 promotes lignan synthesis to regulate root growth and abiotic stress tolerance by modulating ROS homeostasis in Arabidopsis
- The conserved function of bHLH121 and overexpression of N-terminal bHLH121 fragment suppresses iron deficiency response in Arabidopsis
- A bivalent chromatin reader-WOX5 module maintains root stem cell niche in Arabidopsis
- Snurportin-1 maintains muscle niche integrity and myogenic progenitor homeostasis
BibTeX
@misc{zhou2026bhlh121cat2,
title = {{The bHLH121-CAT2 module maintains root tip redox homeostasis to confer salt tolerance additively with the SOS pathway in Arabidopsis}},
author = {P. Zhou and C. Liu and Y. Pan and R. Wang and Y. Fei and B. Liu and X. Du and M. I. Hossen and Y. Chen and L. Liang and R. Shen and P. Lan},
howpublished = {bioRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.02.763515},
url = {https://www.biorxiv.org/content/10.64898/2026.11.02.763515v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - The bHLH121-CAT2 module maintains root tip redox homeostasis to confer salt tolerance additively with the SOS pathway in Arabidopsis
AU - P. Zhou
AU - C. Liu
AU - Y. Pan
AU - R. Wang
AU - Y. Fei
AU - B. Liu
AU - X. Du
AU - M. I. Hossen
AU - Y. Chen
AU - L. Liang
AU - R. Shen
AU - P. Lan
PY - 2026
DA - 2026/11/02
PB - bioRxiv
DO - 10.64898/2026.11.02.763515
UR - https://www.biorxiv.org/content/10.64898/2026.11.02.763515v1
AB - Soil salinity inhibits plant growth, in part, by restricting the availability of essential mineral nutrients such as iron (Fe). Although Fe deficiency frequently coincides with salt stress in the field, the molecular mechanisms integrating Fe homeostasis with salt tolerance remain largely unknown. Here, we identify the Fe deficiency response regulator bHLH121 as a key coordinator of salt tolerance in Arabidopsis. Loss-of-function mutants of bHLH121 exhibit pronounced hypersensitivity to salt stress, with severely impaired primary root elongation and reduced seedling biomass. Transcriptomic and histochemical analyses reveal that bHLH121 is required to maintain reactive oxygen species (ROS) homeostasis specifically in root tips under salt stress. We further demonstrate that CATALASE 2 (CAT2) is a direct downstream target of bHLH121, and that CAT2 overexpression fully rescues the salt hypersensitivity of the bhlh121 mutant. Importantly, this bHLH121-CAT2 module operates independently of the classical SOS pathway, as sos2 bhlh121 double mutants display additive salt sensitivity. Together, our findings uncover a novel regulatory module in which bHLH121 governs root tip redox homeostasis through CAT2 to confer salt tolerance, providing a direct mechanistic link between the Fe regulatory network and abiotic stress resilience in plants.
ER -