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A Model to Incorporate the bHLH Transcription Factor OsIRO3 within the Rice Iron Homeostasis Regulatory Network

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posted on 20.09.2022, 06:52 authored by O Carey-Fung, Martin O'BrienMartin O'Brien, JT Beasley, AAT Johnson
Iron (Fe) homeostasis in plants is governed by a complex network of regulatory elements and transcription factors (TFs), as both Fe toxicity and deficiency negatively impact plant growth and physiology. The Fe homeostasis network is well characterized in Arabidopsis thaliana and remains poorly understood in monocotyledon species such as rice (Oryza sativa L.). Recent investigation of the rice Fe homeostasis network revealed OsIRO3, a basic Helix–Loop–Helix (bHLH) TF as a putative negative regulator of genes involved in Fe uptake, transport, and storage. We employed CRISPR-Cas9 gene editing to target the OsIRO3 coding sequence and generate two independent T-DNA-free, loss-of-function iro3 mutants in rice cv. Nipponbare. The iro3 mutant plants had similar phenotype under nutrient-sufficient conditions and had stunted growth under Fe-deficient conditions, relative to a T-DNA free, wild-type control (WT). Under Fe deficiency, iro3 mutant shoots had reduced expression of Fe chelator biosynthetic genes (OsNAS1, OsNAS2, and OsNAAT1) and upregulated expression of an Fe transporter gene (OsYSL15), relative to WT shoots. We place our results in the context of the existing literature and generate a model describing the role of OsIRO3 in rice Fe homeostasis and reinforce the essential function of OsIRO3 in the rice Fe deficiency response.

Funding

This research was supported by grants to A.A.T.J. from the Australian Research Council (LP130100785 and LP190100631) and HarvestPlus.

History

Publication Date

31/01/2022

Journal

International Journal of Molecular Sciences

Volume

23

Issue

3

Article Number

1635

Pagination

13p.

Publisher

MDPI

ISSN

1661-6596

Rights Statement

© 2022 by the authors.This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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