J Integr Plant Biol. ›› 2022, Vol. 64 ›› Issue (5): 1059-1075.DOI: 10.1111/jipb.13251

• Molecular Physiology • Previous Articles     Next Articles

The miR157-SPL-CNR module acts upstream of bHLH101 to negatively regulate iron deficiency responses in tomato

Huihui Zhu1†, Jiayi Wang1†, Dan Jiang2, Yiguo Hong2, Jiming Xu1, Shaojian Zheng1, Jianli Yang1* and Weiwei Chen1,2*   

  1. 1 State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
    2 Research Centre for Plant RNA Signaling, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China

    These authors contributed equally to this work.
    *Correspondences: Jianli Yang (yangjianli@zju.edu.cn;); Weiwei Chen (chenweiwei@hznu.edu.cn; Dr. Chen is fully responsible for the distributions of all materials associated with this article)
  • Received:2022-01-29 Accepted:2022-03-14 Online:2022-04-22 Published:2022-05-01


Iron (Fe) homeostasis is critical for plant growth, development, and stress responses. Fe levels are tightly controlled by intricate regulatory networks in which transcription factors (TFs) play a central role. A series of basic helix-loop-helix (bHLH) TFs have been shown to contribute to Fe homeostasis, but the regulatory layers beyond bHLH TFs remain largely unclear. Here, we demonstrate that the SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) TF SlSPL-CNR negatively regulates Fe-deficiency responses in tomato (Solanum lycopersicum) roots. Fe deficiency rapidly repressed the expression of SlSPL-CNR, and Fe deficiency responses were intensified in two clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9-generated SlSPL-CNR knock-out lines compared to the wild-type. Comparative transcriptome analysis identified 47 Fe deficiency-responsive genes the expression of which is negatively regulated by SlSPL-CNR, one of which, SlbHLH101, helps regulate Fe uptake genes. SlSPL-CNR localizes the nucleus and interacts with the GTAC and BOX 4 (ATTAAT) motifs in the SlbHLH101 promoter to repress its expression. Inhibition of SlSPL-CNR expression in response to Fe deficiency was well correlated with the expression of the microRNA SlymiR157. SlymiR157-overexpressing tomato lines displayed enhanced Fe deficiency responses, as did SlSPL-CNR loss-of-function mutants. We propose that the SlymiR157-SlSPL-CNR module represents a novel pathway that acts upstream of SlbHLH101 to regulate Fe homeostasis in tomato roots.

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