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A cell wall extract from the endophytic fungus Piriformospora indica promotes growth of Arabidopsis seedlings and induces intracellular calcium elevation in roots
Author(s) -
Vadassery Jyothilakshmi,
Ranf Stefanie,
Drzewiecki Corinna,
Mithöfer Axel,
Mazars Christian,
Scheel Dierk,
Lee Justin,
Oelmüller Ralf
Publication year - 2009
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2009.03867.x
Subject(s) - aequorin , arabidopsis , biology , microbiology and biotechnology , extracellular , arabidopsis thaliana , nicotiana tabacum , signal transduction , staurosporine , cytosol , kinase , botany , protein kinase a , intracellular , mutant , biochemistry , gene , enzyme
Summary Calcium (Ca 2+ ), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca 2+ ] 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 Ca 2+ signalling‐related functions. The CWE induces a transient cytosolic Ca 2+ ([Ca 2+ ] cyt ) elevation in the roots of Arabidopsis and tobacco ( Nicotiana tabacum ) plants, as well as in BY‐2 suspension cultures expressing the Ca 2+ bioluminescent indicator aequorin. Nuclear Ca 2+ transients were also observed in tobacco BY‐2 cells. The Ca 2+ response was more pronounced in roots than in shoots and involved Ca 2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca 2+ response by staurosporine and the refractory nature of the Ca 2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H 2 O 2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen‐activated protein kinases (MAPKs) in a Ca 2+ ‐dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica . Thus, Ca 2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco.