Authors:
Marta-Marina Pérez-Alonso1,2, Carmen Guerrero-Galán1, Adrián González Ortega-Villaizán1, Paloma Ortiz-García1, Sandra S. Scholz3, Patricio Ramos4, Hitoshi Sakakibara5,6, Takatoshi Kiba5,6, Jutta Ludwig-Müller7, Anne Krapp8, Ralf Oelmüller3, Jesús Vicente-Carbajosa1,9 and Stephan Pollmann1,9*
1Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)–Instituto Nacional de Investigación y Tecnología Agraria y Alimentación (INIA), Campus de Montegancedo, 28223 Pozuelo de Alarcón (Madrid), Spain
2Umeå Plant Science Center, Umeå University, 90736 Umeå, Sweden
3Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Department of Plant Physiology, Friedrich-Schiller-University Jena, 07743 Jena, Germany
4Centro de Investigación de Estudios Avanzados del Maule, Universidad Católica del Maule, 3460000 Talca, Chile
5RIKEN Center for Sustainable Resource Science, 1-7-22, Suehiro, Tsurumi, Yokohama, 230-0045, Japan
6Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601, Japan
7Institute of Botany, Technische Universität Dresden, 01062 Dresden, Germany
8Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin, 78000 Versailles, France
9Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid (UPM), 28040 Madrid, Spain
* Correspondence: Stephan Pollmann stephan.pollmann@upm.es
Keywords: Arabidopsis thaliana , Ca2+ signaling, Endosymbiosis, Growth promotion, Plant defense, Plant-microbe interaction, Plant performance, Serendipita indica
Abstract
Calcium (Ca2+) is an important second messenger in plants. The activation of Ca2+ signaling cascades is critical in the activation of adaptive processes in response to perceived environmental stimuli, including biotic stresses. The colonization of roots by the plant growth promoting endophyteSerendipita indica involves the increase of cytosolic Ca2+ levels in Arabidopsis thaliana . In this study, we investigated transcriptional changes in Arabidopsis roots during symbiosis with S. indica . RNA-seq profiling disclosed the significant induction of CALCINEURIN B-LIKE 7 (CBL7 ) during early- and later phases of the interaction. Consistent with the transcriptomics analysis, reverse genetic evidence and yeast two-hybrid studies highlighted the functional relevance of CBL7 and tested the involvement of a CBL7-CBL-INTERACTING PROTEIN KINASE 13 (CIPK13) signaling pathway in the establishment of the mutualistic relationship that promotes plant growth. The loss-of-function of CBL7abolished the growth promoting effect of S. indica and affected the colonization of the root by the fungus. The subsequent transcriptomics analysis of cbl7 revealed the involvement of this Ca2+ sensor in activating plant defense responses. Furthermore, we report on the contribution of CBL7 to potassium transport in Arabidopsis. Triggered by the differential expression of a small number of K+ channels/transporter genes, we analyzed K+ contents in wild-type and cbl7plants and observed a significant accumulation of K+in root of cbl7 plants, while shoot tissues demonstrated K+ depletion. Taken together, our work associates CBL7 with an important role in the mutual interaction between Arabidopsis andS. indica and links the CBL7 Ca2+ receptor protein to K+ transport.
Significance statement: The induction of CBL7 is critical for the establishment of the mutual interaction betweenArabidopsis thaliana and its root colonizing endophyteSerendipita indica . Moreover, CBL7 plays a vital role in K+ distribution during the plant-fungus interaction.