A cell wall extract from the endophytic fungus Piriformospora indica promotes growth of Arabidopsis seedlings and induces intracellular calcium elevation in roots.
Calcium (Ca2+), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca2+] elevations are early events in the interaction between the plant growth-promoting fungus Piriformospora indica and Arabidopsis thaliana. A cell wall extract (CWE) from the fungus promotes the growth of wild-type seedlings but not of seedlings from P. indica-insensitive mutants. The extract and the fungus also induce a similar set of genes in Arabidopsis roots, among them genes with Ca2+ signalling-related functions. The CWE induces a transient cytosolic Ca2+ ([Ca2+](cyt)) elevation in the roots of Arabidopsis and tobacco (Nicotiana tabacum) plants, as well as in BY-2 suspension cultures expressing the Ca2+ bioluminescent indicator aequorin. Nuclear Ca2+ transients were also observed in tobacco BY-2 cells. The Ca2+ response was more pronounced in roots than in shoots and involved Ca2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca2+ response by staurosporine and the refractory nature of the Ca2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H2O2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen-activated protein kinases (MAPKs) in a Ca2+-dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica. Thus, Ca2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco.
Vadassery
Jyothilakshmi
J
Friedrich-Schiller-Universität Jena, Institut für Allgemeine Botanik und Pflanzenphysiologie, Dornburger Street 159, D-07743 Jena, Germany.
Ranf
Stefanie
S
Drzewiecki
Corinna
C
Mithöfer
Axel
A
Mazars
Christian
C
Scheel
Dierk
D
Lee
Justin
J
Oelmüller
Ralf
R
D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D001487:Basidiomycota / Q000737:chemistry*; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002473:Cell Wall / Q000737:chemistry*; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018749:RNA, Plant / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
D018749:RNA, Plant; D000331:Aequorin; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium