Copper (Cu) availability is of crucial importance for plant growth and development and for the yield and quality of food. It is crucial for plants to maintain Cu homeostasis. To maintain Cu homeostasis in different tissues and organs, the uptake and transport of Cu must be precisely controlled.

IRON MAN (IMA) is a family of small peptides that can bind both iron (Fe) and Cu ions. It was reported that IMAs mediate Fe homeostasis in Arabidopsis thaliana. However, it remains unclear whether IMAs are involved in Cu homeostasis.

In a study published in New Phytologist, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) revealed that IMAs interact with Cu-DEFICIENCY INDUCED TRANSCRIPTION FACTOR1 (CITF1) to maintain  Cu homeostasis in plants.  

The researchers first tested whether the expression of IMA genes is responsive to change in Cu concentration and found that the transcription of IMA genes is repressed by Cu deficiency. The combined disruption of ·all IMA genes caused enhanced tolerance to Cu deficiency and resulted in an increase in the transcript abundance of Cu uptake genes, whereas the overexpression of IMA1 or IMA3 led to the opposite results. 

The researchers then conducted protein interaction assays studies and found that IMAs interact with Cu-DEFICIENCY INDUCED TRANSCRIPTION FACTOR1 (CITF1), which is a positive regulator of the Cu uptake genes. Furthermore, IMAs not only interfere with the DNA binding of CITF1 but also repress the transcriptional activation activity of CITF1, hence resulting in downregulation of the Cu uptake genes. When Cu is sufficient, IMAs block CITF1 from binding to the promoters of the Cu uptake genes and stop CITF1 from activating the Cu uptake genes. When Cu is deficient, the expression of IMAs is repressed.  

The results suggest that IMAs physically interact with CITF1 and negatively regulate the Cu deficiency response by restraining the DNA binding and transcriptional activation of CITF1.  

"This study suggests that IMAs are a new component in the Cu deficiency response signaling pathway. It provides experimental support for the existence of an elaborate system that allows plants to respond dynamically to Cu status,” said LIANG Gang of XTBG. 

Contact 

LIANG Gang Ph.D Principal Investigator         

Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun 666303, Yunnan, China                         

E-mail:  lianggang@xtbg.ac.cn   

First published: 30 November, 2023