Arabidopsis thaliana rapid alkalinization factor 1–mediated root growth inhibition is dependent on calmodulin-like protein 38

Arabidopsis thaliana rapid alkalinization factor 1 (AtRALF1) is a small secreted peptide hormone that inhibits root growth by repressing cell expansion. Although it is known that AtRALF1 binds the plasma membrane receptor FERONIA and conveys its signals via phosphorylation, the AtRALF1 signaling pat...

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Published in:	The Journal of biological chemistry Vol. 293; no. 6; pp. 2159 - 2171
Main Authors:	Campos, Wellington F., Dressano, Keini, Ceciliato, Paulo H.O., Guerrero-Abad, Juan Carlos, Silva, Aparecida Leonir, Fiori, Celso S., Morato do Canto, Amanda, Bergonci, Tábata, Claus, Lucas A.N., Silva-Filho, Marcio C., Moura, Daniel S.
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 09-02-2018 American Society for Biochemistry and Molecular Biology
Subjects:	Arabidopsis Arabidopsis Proteins - metabolism Arabidopsis Proteins - physiology Calcium - pharmacology calmodulin (CaM) Calmodulin - metabolism Calmodulin - physiology cell growth cell signaling development Hydrogen-Ion Concentration peptide hormone Peptide Hormones - metabolism Peptide Hormones - physiology Plant Biology Plant Roots - drug effects Plant Roots - growth & development Plant Roots - metabolism Protein Binding - drug effects rapid alkalinization factor root secreted protein secretory pathway development cell signaling root calmodulin (CaM) cell growth rapid alkalinization factor secretory pathway peptide hormone secreted protein
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Summary:	Arabidopsis thaliana rapid alkalinization factor 1 (AtRALF1) is a small secreted peptide hormone that inhibits root growth by repressing cell expansion. Although it is known that AtRALF1 binds the plasma membrane receptor FERONIA and conveys its signals via phosphorylation, the AtRALF1 signaling pathway is largely unknown. Here, using a yeast two-hybrid system to search for AtRALF1-interacting proteins in Arabidopsis, we identified calmodulin-like protein 38 (CML38) as an AtRALF1-interacting partner. We also found that CML38 and AtRALF1 are both secreted proteins that physically interact in a Ca2+- and pH-dependent manner. CML38-knockout mutants generated via T-DNA insertion were insensitive to AtRALF1, and simultaneous treatment with both AtRALF1 and CML38 proteins restored sensitivity in these mutants. Hybrid plants lacking CML38 and having high accumulation of the AtRALF1 peptide did not exhibit the characteristic short-root phenotype caused by AtRALF1 overexpression. Although CML38 was essential for AtRALF1-mediated root inhibition, it appeared not to have an effect on the AtRALF1-induced alkalinization response. Moreover, acridinium-labeling of AtRALF1 indicated that the binding of AtRALF1 to intact roots is CML38-dependent. In summary, we describe a new component of the AtRALF1 response pathway. The new component is a calmodulin-like protein that binds AtRALF1, is essential for root growth inhibition, and has no role in AtRALF1 alkalinization.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Research fellow of CNPq. These authors contributed equally to this work. Edited by Joseph M. Jez Supported by a fellowship from FAPESP. Supported by a fellowship from CNPq. Supported by a fellowship from CAPES.
ISSN:	0021-9258 1083-351X
DOI:	10.1074/jbc.M117.808881