dominant function of CCaMK in intracellular accommodation of bacterial and fungal endosymbionts

• Published in: The Plant journal : for cell and molecular biology Vol. 63; no. 1; pp. 141 - 154
• Main Authors: Hayashi, Teruyuki, Banba, Mari, Shimoda, Yoshikazu, Kouchi, Hiroshi, Hayashi, Makoto, Imaizumi-Anraku, Haruko
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.07.2010; Blackwell Publishing Ltd; Blackwell
• Subjects: arbuscular mycorrhizal symbiosis; Bacteria; Bacteria - growth & development; Biological and medical sciences; Calcium - metabolism; Calcium-Calmodulin-Dependent Protein Kinases - genetics; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; CCaMK; Cells; common symbiosis genes; Fundamental and applied biological sciences. Psychology; Fungi; Gene Expression Regulation, Plant; Genetic Complementation Test; intracellular infection; Legumes; Lotus - enzymology; Lotus - genetics; Lotus - microbiology; Mutation; Mycorrhizae - growth & development; Original; Parasitism and symbiosis; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Root Nodulation - genetics; root nodule symbiosis; Symbiosis; Symbiosis - genetics; Transformation, Genetic; Symbiosis; Root; Plant nodule; intracellular infection; common symbiosis genes; CCaMK; Infection; Gene; Mycorrhiza; arbuscular mycorrhizal symbiosis; Bacteria; Intracellular; root nodule symbiosis
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313x.2010.04228.x

In legumes, Ca²⁺/calmodulin-dependent protein kinase (CCaMK) is a component of the common symbiosis genes that are required for both root nodule (RN) and arbuscular mycorrhiza (AM) symbioses and is thought to be a decoder of Ca²⁺ spiking, one of the earliest cellular responses to microbial signals. A gain-of-function mutation of CCaMK has been shown to induce spontaneous nodulation without rhizobia, but the significance of CCaMK activation in bacterial and/or fungal infection processes is not fully understood. Here we show that a gain-of-function CCaMKT²⁶⁵D suppresses loss-of-function mutations of common symbiosis genes required for the generation of Ca²⁺ spiking, not only for nodule organogenesis but also for successful infection of rhizobia and AM fungi, demonstrating that the common symbiosis genes upstream of Ca²⁺ spiking are required solely to activate CCaMK. In RN symbiosis, however, CCaMKT²⁶⁵D induced nodule organogenesis, but not rhizobial infection, on Nod factor receptor (NFRs) mutants. We propose a model of symbiotic signaling in host legume plants, in which CCaMK plays a key role in the coordinated induction of infection thread formation and nodule organogenesis.