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A CCaMK/Cyclops response element in the promoter of Lotus japonicus calcium‐binding protein 1 ( CBP1 ) mediates transcriptional activation in root symbioses
Author(s) -
Gong Xiaoyun,
Jensen Elaine,
Bucerius Simone,
Parniske Martin
Publication year - 2022
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.18112
Subject(s) - biology , transactivation , reporter gene , gene , promoter , gene expression , genetics , regulation of gene expression , mutant , microbiology and biotechnology
Summary Early gene expression in arbuscular mycorrhiza (AM) and the nitrogen‐fixing root nodule symbiosis (RNS) is governed by a shared regulatory complex. Yet many symbiosis‐induced genes are specifically activated in only one of the two symbioses. The Lotus japonicus T‐DNA insertion line T90, carrying a promoterless uidA ( GUS ) gene in the promoter of Calcium Binding Protein 1 ( CBP1 ) is exceptional as it exhibits GUS activity in both root endosymbioses. To identify the responsible cis‐ and trans ‐acting factors, we subjected deletion/modification series of CBP1 promoter : reporter fusions to transactivation and spatio‐temporal expression analysis and screened ethyl methanesulphonate (EMS)‐mutagenized T90 populations for aberrant GUS expression. We identified one cis‐ regulatory element required for GUS expression in the epidermis and a second element, necessary and sufficient for transactivation by the calcium and calmodulin‐dependent protein kinase (CCaMK) in combination with the transcription factor Cyclops and conferring gene expression during both AM and RNS. Lack of GUS expression in T90 white mutants could be traced to DNA hypermethylation detected in and around this element. We concluded that the CCaMK/Cyclops complex can contribute to at least three distinct gene expression patterns on its direct target promoters NIN (RNS), RAM1 (AM), and CBP1 (AM and RNS), calling for yet‐to‐be identified specificity‐conferring factors.