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 lyco-persicum) roots. Fe deficiency rapidly repressed the expression of SlSPL-CNR, and Fe deficiency re-sponses 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 neg-atively 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 mu-tants. We propose that the SlymiR157-SlSPL-CNR module represents a novel pathway that acts upstream of SlbHLH101 to regulate Fe homeostasis in tomato roots.

Huihui Zhu;Jiayi Wang;Dan Jiang;Yiguo Hong;Jiming Xu;Shaojian Zheng;Jianli Yang;Weiwei Chen

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

植物学报（英文版）

[1]Huihui Zhu;Jiayi Wang;Dan Jiang;Yiguo Hong;Jiming Xu;Shaojian Zheng;Jianli Yang;Weiwei Chen-.The miR157-SPL-CNR module acts upstream of bHLH101 to negatively regulate iron deficiency responses in tomato)[J].植物学报（英文版）,2022(05):1059-1075

miR157,bHLH101,PROMOTER,SlSPL,lyco,SlbHLH101,GTAC,ATTAAT,SlymiR157

CNR,module,upstream,negatively,iron,deficiency,responses,tomato,Iron,homeostasis,critical,plant,growth,development,stress,levels,tightly,controlled,by,intricate,regulatory,networks,which,transcription,factors,TFs,central,role,series,basic,helix,loop,have,been,shown,contribute,layers,beyond,remain,largely,unclear,Here,demonstrate,that,SQUAMOSA,BINDING,PROTEIN,LIKE,regulates,Solanum,persicum,roots,rapidly,repressed,expression,were,intensified,clustered,regularly,interspaced,palindromic,repeats,CRISPR,associated,protein,generated,knock,out,lines,compared,wild,type,Comparative,transcriptome,analysis,identified,responsive,genes,regulated,one,helps,uptake,localizes,nucleus,interacts,BOX,motifs,promoter,its,Inhibition,was,well,correlated,microRNA,overexpressing,displayed,enhanced,did,loss,function,mu,tants,We,propose,represents,novel,pathway

0.452656