Phosphorylation of S344 in the calmodulin‐binding domain negatively affects CCaMK function during bacterial and fungal symbioses

Citations Over TimeTop 10% of 2013 papers

Abstract

Calcium and Ca(2+)/calmodulin-dependent protein kinase (CCaMK) plays a critical role in the signaling pathway that establishes root nodule symbiosis and arbuscular mycorrhizal symbiosis. Calcium-dependent autophosphorylation is central to the regulation of CCaMK, and this has been shown to promote calmodulin binding. Here, we report a regulatory mechanism of Medicago truncatula CCaMK (MtCCaMK) through autophosphorylation of S344 in the calmodulin-binding/autoinhibitory domain. The phospho-ablative mutation S344A did not have significant effect on its kinase activities, and supports root nodule symbiosis and arbuscular mycorrhizal symbiosis, indicating that phosphorylation at this position is not required for establishment of symbioses. The phospho-mimic mutation S344D show drastically reduced calmodulin-stimulated substrate phosphorylation, and this coincides with a compromised interaction with calmodulin and its interacting partner, IPD3. Functional complementation tests revealed that the S344D mutation blocked root nodule symbiosis and reduced the mycorrhizal association. Furthermore, S344D was shown to suppress the spontaneous nodulation associated with a gain-of-function mutant of MtCCaMK (T271A), revealing that phosphorylation at S344 of MtCCaMK is adequate for shutting down its activity, and is epistatic over previously identified T271 autophosphorylation. These results reveal a mechanism that enables CCaMK to 'turn off' its function through autophosphorylation.

Related Papers

• → A Medicago truncatula SWEET transporter implicated in arbuscule maintenance during arbuscular mycorrhizal symbiosis(2019)142 cited
• → Activation of type II calcium/calmodulin-dependent protein kinase by Ca2+/calmodulin is inhibited by autophosphorylation of threonine within the calmodulin-binding domain.(1990)170 cited
• → Detailed state model of CaMKII activation and autophosphorylation(2008)48 cited
• → Medicago truncatula(2013)4 cited
• → Adapting the Lateral Root-Inducible System to Medicago truncatula(2018)2 cited