A nutrient-regulated, dual localization phospholipase A(2) in the symbiotic fungus Tuber borchii.
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, Ca(2+)-dependent phospholipase from the mycorrhizal fungus Tuber borchii. TbSP1 is the first phospholipase A(2) 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 A(2) 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 A(2) in the organization of multicellular filamentous structures in bacteria and fungi.
Soragni
E
E
Dipartimento di Biochimica e Biologia Molecolare, Università di Parma, Parco Area delle Scienze 23/A, I-43100 Parma, Italy.
Bolchi
A
A
Balestrini
R
R
Gambaretto
C
C
Percudani
R
R
Bonfante
P
P
Ottonello
S
S
D000595:Amino Acid Sequence; D001203:Ascomycota / Q000201:enzymology* / Q000648:ultrastructure; D002118:Calcium / Q000494:pharmacology; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D003470:Culture Media; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D021381:Protein Transport; D012331:RNA, Fungal / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis; D015854:Up-Regulation
D003470:Culture Media; D005656:Fungal Proteins; D012331:RNA, Fungal; D010741:Phospholipases A; D002118:Calcium