School of BioSciences, The University of Melbourne, Parkville, VIC 3010, Australia.
Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, VIC 3086, Australia.
Int J Mol Sci. 2022 Jan 31;23(3):1635. doi: 10.3390/ijms23031635.
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 and remains poorly understood in monocotyledon species such as rice ( 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 coding sequence and generate two independent T-DNA-free, loss-of-function mutants in rice cv. Nipponbare. The 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, mutant shoots had reduced expression of Fe chelator biosynthetic genes ( and ) and upregulated expression of an Fe transporter gene (), 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.
植物体内的铁（Fe）稳态是由一个复杂的调节元件和转录因子（TF）网络控制的，因为Fe 毒性和缺乏都会对植物的生长和生理产生负面影响。在 和 中，Fe 稳态网络得到了很好的描述，但在单子叶植物物种如水稻（L.）中仍然知之甚少。最近对水稻 Fe 稳态网络的研究揭示了 OsIRO3，作为一种潜在的负调控因子，参与 Fe 吸收、转运和储存的基因。我们利用 CRISPR-Cas9 基因编辑靶向编码序列，并在水稻 cv. Nipponbare 中生成了两个独立的 T-DNA 缺失、功能丧失的 突变体。与 T-DNA 自由、野生型对照（WT）相比， 突变体植物在养分充足的条件下具有相似的表型，在缺铁条件下生长不良。在缺铁条件下， 突变体的地上部中 Fe 螯合生物合成基因（和）的表达减少，而 Fe 转运基因（）的表达上调，与 WT 的地上部相比。我们将我们的结果置于现有文献的背景下，并提出了一个模型，描述了 OsIRO3 在水稻 Fe 稳态中的作用，并强调了 OsIRO3 在水稻缺铁反应中的重要功能。
