日前，中山大学生命科学大学院王宏斌教授团队在植物铁稳态调控机制方面取得新进展，发现bHLH转录因子家族成员通过级联调控的方式，响应缺铁胁迫应答并参与植物体内铁稳态调控。研究成果已发表于《The Plant Cell》，该工作得到了国家杰出青年科学基金资助。

目前，缺铁已成为最普遍的营养缺乏症之一，当前植物仍是人类摄取铁元素的主要食用来源。因此，系统地了解植物的铁吸收运输及其稳态调控机制，对农作物铁营养价值的改良具有非常重要的意义。

植物体内存在复杂的铁稳态调控系统。一方面，植物需要能够对生长土壤中缺铁胁迫进行应答，以保证有效的铁吸收；另一方面，植物需要对体内铁含量进行调控，以避免过量的铁对其自身生长发育产生的毒害。bHLH转录因子家族在植物缺铁应答中起重要作用，但是其精细调控网络尚不清楚。

王宏斌团队通过对拟南芥突变体大规模筛选，发现bHLH转录因子IVc亚家族成员bHLH104与ILR3可以协同作用，参与植物对于缺铁胁迫的应答。进一步研究表明，bHLH104与ILR3可以直接调控铁吸收相关重要转录因子——bHLH转录因子Ib亚家族基因以及PYE基因的表达，从而激活下游铁吸收及转运直接相关基因。有趣的是，遗传学分析提示bHLH104/ILR3可能是铁吸收负调控因子E3泛素连接酶BTS的下游靶标，以此防止植物对铁的过量吸收。这一研究工作揭示了植物铁稳态调控过程中转录因子间的级联调控模式，进一步阐明了植物铁稳态调控机制。（来源：中国科学报 张晴丹）

The bHLH Transcription Factor bHLH104 Interacts with IAA-LEUCINE RESISTANT3 and Modulates Iron Homeostasis in Arabidopsis

Abstract  Iron (Fe) is an indispensable micronutrient for plant growth and development. The regulation of Fe homeostasis in plants is complex and involves a number of transcription factors. Here, we demonstrate that a basic helix-loop-helix (bHLH) transcription factor, bHLH104, belonging to the IVc subgroup of bHLH family, acts as a key component positively regulating Fe deficiency responses. Knockout of bHLH104 in Arabidopsis thaliana greatly reduced tolerance to Fe deficiency, whereas overexpression of bHLH104 had the opposite effect and led to accumulation of excess Fe in soil-grown conditions. The activation of Fe deficiency-inducible genes was substantially suppressed by loss of bHLH104. Further investigation showed that bHLH104 interacted with another IVc subgroup bHLH protein, IAA-LEUCINE RESISTANT3 (ILR3), which also plays an important role in Fe homeostasis. Moreover, bHLH104 and ILR3 could bind directly to the promoters of Ib subgroup bHLH genes and POPEYE (PYE) functioning in the regulation of Fe deficiency responses. Interestingly, genetic analysis showed that loss of bHLH104 could decrease the tolerance to Fe deficiency conferred by the lesion of BRUTUS, which encodes an E3 ligase and interacts with bHLH104. Collectively, our data support that bHLH104 and ILR3 play pivotal roles in the regulation of Fe deficiency responses via targeting Ib subgroup bHLH genes and PYE expression.

原文链接：http://www.plantcell.org/content/27/3/787.full.pdf+html