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The auxin‐inducible GH3 homologue Pp‐GH3.16 is downregulated in Pinus pinaster root systems on ectomycorrhizal symbiosis establishment
Author(s) -
Reddy S. M.,
Hitchin S.,
Melayah D.,
Pandey A. K.,
Raffier C.,
Henderson J.,
Marmeisse R.,
Gay G.
Publication year - 2006
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2006.01677.x
Subject(s) - auxin , biology , symbiosis , abscisic acid , mutant , downregulation and upregulation , lateral root , botany , pinus pinaster , stele , microbiology and biotechnology , gene , arabidopsis , biochemistry , genetics , bacteria
Summary• In an attempt to determine whether auxin‐regulated plant genes play a role in ectomycorrhizal symbiosis establishment, we screened a Pinus pinaster root cDNA library for auxin‐upregulated genes. This allowed the identification of a cDNA, Pp‐GH3.16 , which encodes a polypeptide sharing extensive homologies with GH3 proteins of different plants. • Pp‐GH3.16 was specifically upregulated by auxins and was not affected by cytokinin, gibberellin, abscisic acid or ethylene, or by heat shock, water stress or anoxia. • Pp‐GH3.16 mRNAs were quantified in pine roots inoculated with two ectomycorrhizal fungi, Hebeloma cylindrosporum and Rhizopogon roseolus . Surprisingly, Pp‐GH3.16 was downregulated following inoculation with both fungal species. The downregulation was most rapid on establishment of symbiosis with an indole‐3‐acetic acid (IAA)‐overproducing mutant of H. cylindrosporum , which overproduced mycorrhizas characterized by a hypertrophic Hartig net. This indicates that, despite being auxin‐inducible, Pp‐GH3.16 can be downregulated on establishment of symbiosis with a fungus that releases auxin. • By contrast, Pp‐GH3.16 was not downregulated in pine root systems inoculated with a nonmycorrhizal mutant of H. cylindrosporum , suggesting that the downregulation we observed in mycorrhizal root systems was a component of the molecular cross‐talk between symbiotic partners at the origin of differentiation of symbiotic structures.