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

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.

Keywords

• iron
• transcription regulation
• fe deficiency response
• fe homeostasis
• arabidopsis thaliana