Abstract：
Iron is an essential micronutrient for plant growth and development. In Arabidopsis thaliana, an intricate regulatory network involving several basic helix-loop-helix (bHLH) transcription factors controls the homeostasis of iron. Among these transcription factors, bHLH121 plays a crucial role. bHLH121 interacts in vivo with clade IVc bHLH transcription factors and activates the expression of FIT and clade Ib bHLH transcription factors to stimulate the uptake of iron. How bHLH121 and clade IVc bHLH transcription factors function collectively and efficiently to maintain iron homeostasis is still unclear. Herein, we found that double loss-of-function mutants involving bhlh121 and one of the clade IVc bHLH transcription factors displayed more severe iron deficiency-associated growth defects than each of the single mutants. We also found that among the four clade IVc bHLH transcription factors, only bHLH34 and bHLH105 could partially complement the iron-associated growth defects of bhlh121 when overexpressed. These data, together with protein localization analysis, support that bHLH121 and clade IVc bHLH transcription factors act synergistically to regulate iron homeostasis and that different bHLH121/clade IVc and clade IVc/clade IVc protein complexes are involved in this process.
摘要：
铁是植物生长发育必需的微量营养素。在拟南芥中，涉及多种bHLH转录因子（TFs）的复杂调节网络控制铁的稳态。在这些TFs中，bHLH121起着至关重要的作用。bHLH121在体内与进化枝IVcbHLHTF相互作用，并激活FIT和进化枝IbbHLHTF的表达，以刺激铁的摄取。目前尚不清楚bHLH121和进化枝IVcbHLHTFs如何共同有效地维持铁稳态。在这里，我们发现，涉及bhlh121和一个进化枝IVcbHLH的双重功能丧失突变体显示出比每个单一突变体更严重的缺铁性生长缺陷。我们还发现，在四个分支IVcbHLHTF中，当bHLH34和bHLH105过表达时，可以部分补充bhlh121与铁相关的生长缺陷。这些数据,以及蛋白质定位分析，支持bHLH121和进化枝IVcbHLHTF协同作用以调节铁稳态，并且不同的bHLH121/进化枝IVc和进化枝IVc/进化枝IVc蛋白复合物参与此过程。
