The bHLH protein OsIRO3 is critical for plant survival and iron (Fe) homeostasis in rice (Oryza sativa L.) under Fe-deficient conditions
The bHLH protein OsIRO3 is critical for plant survival and iron (Fe) homeostasis in rice (Oryza sativa L.) under Fe-deficient conditions
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DOI：
10.1080/00380768.2020.1783966
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发表时间：
2020-07
影响因子：
2
通讯作者：
Fan Wang;R. N. Itai;Tomoko Nozoye;Takanori Kobayashi;N. Nishizawa;H. Nakanishi
中科院分区：
文献类型：
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作者：
Fan Wang;R. N. Itai;Tomoko Nozoye;Takanori Kobayashi;N. Nishizawa;H. Nakanishi
摘要铁是大多数生物体的必需元素，参与各种生物反应。缺铁是植物生长发育的主要限制因素，导致作物产量低、营养品质差。植物对铁的吸收和转运需要多个基因的协同表达，而这一过程受到多种转录因子的调控，特别是碱性螺旋-环-螺旋（bHLH）家族成员的调控。OsIRO 3在水稻中的过量表达被认为是根中铁稳态基因调控的抑制子。但其在缺铁条件下对水稻生长和根、茎间铁平衡的调节作用尚不清楚。在这里，我们通过CRISPR/Cas9系统开发了osiro 3敲除突变体。缺铁处理后，osiro 3基因敲除突变体叶片生长发育异常。osiro 3基因敲除突变体的幼叶发生强烈的病变，严重缺铁时甚至导致植株死亡。此外，缺铁胁迫下osiro 3基因敲除突变体地上部活性氧（ROS）的积累、铁和锰浓度均升高。定量RT-PCR结果表明，缺铁处理后，OsNAC 4基因和OsFerritins基因在osiro 3基因敲除的植株中均被激活，其中OsNAC 4基因负责ROS诱导的植物超敏细胞死亡，OsFerritins基因负责铁的储存和超负荷。在osiro 3基因敲除突变体中，铁缺乏反应基因在根中被诱导，但在芽中被抑制，并且根据DNA微阵列，在铁缺乏条件下，铁充足/过载基因在芽中被诱导。酵母双杂交分析显示OsIRO 3和同源蛋白OsbHLH 062之间存在正相互作用，该蛋白在缺铁根中的转录也增加。OsIRO 3是水稻缺铁条件下维持植株存活所必需的，并且在从芽到根的信号传递中起重要作用，这对于植物防止铁超载至关重要。
ABSTRACT Iron (Fe) is an essential element for most organisms since it is involved in various biological reactions. Fe deficiency is a major constraint for plant growth and leads to low crop yields and poor nutritional quality. Fe uptake and translocation in plants require the coordinated expression of multiple genes, which is regulated by various transcription factors (TFs), especially members of the basic helix-loop-helix (bHLH) family. OsIRO3 was first reported as a repressor related to Fe homeostasis gene regulation in roots based on evidence in overexpressing rice. However, its functions in regulating rice growth and Fe homeostasis between roots and shoots during Fe deficiency is poorly understood. Here, we developed osiro3 knockout mutants by the CRISPR/Cas9 system. The leaves of osiro3 knockout mutants showed abnormal growth and development after Fe-deficiency treatment. Strong lesions occurred on the young leaves of osiro3 knockout mutants, which even led to plant death during severe Fe deficiency. Furthermore, accumulation of reactive oxygen species (ROS), Fe and manganese concentrations were all elevated in the shoots of osiro3 knockout mutants under the Fe deficiency stress. Quantitative RT-PCR showed that OsNAC4 for ROS induced plant hypersensitive cell death and OsFerritins for Fe storage and overload were all significantly activated in osiro3 knockout shoots after Fe deficiency treatment. In osiro3 knockout mutants, Fe-deficiency response genes were induced in roots, but suppressed in shoots, and furthermore Fe sufficiency/overload genes were induced in shoots under Fe-deficient conditions according to DNA microarray. Yeast two-hybrid analysis revealed a positive interaction between OsIRO3 and the homologous protein OsbHLH062, which was also transcriptionally increased in Fe-deficient roots. OsIRO3 is essential for maintaining plant survival in rice under Fe-deficient conditions and plays an important role in signal transmission from shoots to roots which is critical for plants to prevent Fe overload.