The interaction apparatus of Asteridiella callista (Meliolaceae, Ascomycota)

Abstract

We document here for the first time ultrastructural details of the cellular interaction of Asteridiella callista and its host Stachytarpheta mutabilis var. violacea from Costa Rica. A. callista attaches to the host with appressoria, invades the epidermal cell wall and forms an apoplastic complex cisternal net, presumably for nutrient uptake from its host. This unique structure, called an interaction apparatus (Ia), consists of cisternae surrounded by a membrane continuous with the fungal cytoplasmic membrane. Subsequently the apoplastic trunk of the Ia extends into the host epidermal cell wall and contacts the host cytoplasmic membrane. Electron-opaque material, probably of fungal origin appears at the host cytoplasmic membrane. Finally these electron-opaque deposits are encased by host material. Functional and systematical aspects of this interaction scenario are discussed.

• appressorium
• cellular interaction
• cisternal tubules
• concentric bodies
• Costa Rica
• Stachytarpheta mutabilis var. violacea
• Verbenaceae

Acknowledgments

We acknowledge DAAD for granting a postdoctoral fellowship at the Universität Tübingen to DRJ and Christiane Karasch-Wittmann for technical support. We thank Dr Amy Rossman, Shannon Dominick and Katie Moss from BPI for the support with the loan of species of Meliolaceae. We thank Ethel Sánchez Chacón of the Centro de Investigación en Estructuras Microscópicas (CIEMIC), Universidad de Costa Rica, for logistical support and the Ministerio del Ambiente, Energía y Telecomunicaciones de Costa Rica (MINAET) for granting collecting permits.