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  • The EMBO Journal (2001) 20, 5079 - 5090
  • doi:10.1093/emboj/20.18.5079

A nutrient-regulated, dual localization phospholipase A2 in the symbiotic fungus Tuber borchii

Elisabetta Soragni2, Angelo Bolchi1, Raffaella Balestrini3, Claudio Gambaretto1, Riccardo Percudani1, Paola Bonfante3 and Simone Ottonello1

  1. Dipartimento di Biochimica e Biologia Molecolare, Università di Parma, Parco Area delle Scienze 23/A, I-43100 Parma
  2. Present address: Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
  3. Centro di Studio sulla Micologia del Terreno (CNR) and Dipartimento di Biologia Vegetale, Università di Torino, Vialle Mattioli 25, I-10125 Torino, Italy

Correspondence to:

Simone Ottonello, E-mail: s.ottonello@unipr.it

Received 20 June 2001; Accepted 1 August 2001; Revised 1 August 2001

Important morphogenetic transitions in fungi are triggered by starvation-induced changes in the expression of structural surface proteins. Here, we report that nutrient deprivation causes a strong and reversible up-regulation of TbSP1, a surface-associated, Ca2+-dependent phospholipase from the mycorrhizal fungus Tuber borchii. TbSP1 is the first phospholipase A2 to be described in fungi and identifies a novel class of phospholipid-hydrolyzing enzymes. The TbSP1 phospholipase, which is synthesized initially as a pre-protein, is processed efficiently and secreted during the mycelial phase. The mature protein, however, also localizes to the inner cell wall layer, close to the plasma membrane, in both free-living and symbiosis-engaged hyphae. It thus appears that a dual localization phospholipase A2 is involved in the adaptation of a symbiotic fungus to conditions of persistent nutritional limitation. Moreover, the fact that TbSP1-related sequences are present in Streptomyces and Neurospora, and not in wholly sequenced non-filamentous microorganisms, points to a general role for TbSP1 phospholipases A2 in the organization of multicellular filamentous structures in bacteria and fungi.

  • Keywords:

    • cell wall,
    • mycorrhizal fungi,
    • phospholipase A2,
    • secretion,
    • starvation