拟南芥bHLH Ib转录因子调控FIT的转录

bHLH Ib transcription factors regulate the transcription of FIT in Arabidopsis thaliana

关键词:  铁, 转录调控, 缺铁响应, 铁稳态, 拟南芥

Key words:  Iron, transcription regulation, Fe deficiency response, Fe homeostasis, Arabidopsis thaliana

摘要:

FIT是调控拟南芥铁稳态的一个关键调控因子,它在转录水平上受到缺铁诱导,但其背后的调控机制还不甚清楚。该研究以拟南芥bHLH38和FIT的单、双过表达植物及bHLH Ib四突变体植物为材料,采用缺铁(-Fe)处理实验和定量RT-PCR的方法从RNA角度分析了FIT转录水平的变化。结果表明:(1)在铁充足时,bHLH38过表达植物中FIT的转录水平显著高于其在野生型中的水平。(2)在bHLH Ib四突变体植物中FIT的转录水平不受缺铁诱导。(3)FIT单过表达不能激活内源FIT的转录,而在加铁(+Fe)条件下bHLH38和FIT的双过表达则可以激活内源FIT的转录。(4)在缺铁条件下,所有植物中FIT的转录水平均与野生型中的FIT水平无明显差异。基于以上结果认为,bHLH Ib转录因子是缺铁诱导FIT转录的必要条件,而非充分条件。该研究结果为深入了解植物通过多种途径共同维持铁稳态提供了新的见解。

Abstract:

FIT(FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR)is a key regulator of Fe homeostasis in Arabidopsis, which is upregulated under Fe deficiency condition, however, the underlying regulatory mechanism is still unclear. In this study, the single and dual overexpression plants of A. thaliana bHLH38 and FIT, as well as the bHLH Ib quadruple mutant plants,were used as research materials, and Fe deficiency test and quantitative RT-PCR were used to analyze the change of FIT transcription level from the perspective of RT-RNA. The results were as follows:(1)Under Fe sufficient condition, the transcription level of FIT significantly increased in the bHLH38 overexpression plants compared with in the wild type plants.(2)The transcription of FIT did not respond to Fe deficiency in the bHLH Ib quadruple mutant plant.(3)The overexpression of FIT could not activate the transcription of native FIT, and the dual overexpression of FIT and bHLH38 promoted the transcription of native FIT under Fe sufficient conditions.(4)There was no significant difference for the expression of FIT between the transgenic or mutant plants and wild type plants under Fe deficiency condition. Taken together, these data suggest that bHLH Ib transcription factors are necessary, but not sufficient, for the upregulation of FIT by Fe deficiency. The results of this study provide new insights into the various ways that plants work together to maintain Fe homeostasis.