Ultrastructure of the Rust Fungus Puccinia miscanthi in the Teliospore Stage Interacting with the Biofuel Plant Miscanthus sinensis

Abstract

Interaction of the the rust fungus Puccinia miscanthi with the biofuel plant Miscanthus sinensis during the teliospore phase was investigated by light and electron microscopy. P. miscanthi telia were oval-shaped and present on both the adaxial and abaxial leaf surfaces. Teliospores were brown, one-septate (two-celled), and had pedicels attached to one end. Transmission electron microscopy revealed numerous electron-translucent lipid globules in the cytoplasm of teliospores. Extensive cell wall dissolution around hyphae was not observed in the host tissues beneath the telia. Hyphae were found between mesophyll cells in the leaf tissues as well as in host cells. Intracellular hyphae, possibly haustoria, possessed electron-dense fungal cell walls encased by an electron-transparent fibrillar extrahaustorial sheath that had an electron-dense extrahaustorial membrane. The infected host cells appeared to maintain their membrane-bound structures such as nuclei and chloroplasts. These results suggest that the rust fungus maintains its biotrophic phase with most mesophyll cells of M. sinensis. Such a nutritional mode would permit the rust fungus to obtain food reserves for transient growth in the course of host alteration.

Infection Strategies and Pathogenicity of Biotrophic Plant Fungal Pathogens

“…An appressorium then forms above the stomata, followed by the development of a penetration peg to invade the host ( Voegele et al, 2009 ). The formation of the penetration peg is initiated by haustorial mother cells, from which some lytic enzymes are secreted to promote successful penetration of the host cell wall, followed by the differentiation of the haustorium in the host cells ( Kim, 2015 ). The continued growth of the peg within the substomatal chamber penetrates the host tissues ( Chethana et al, 2021 ), and the cavity forms a vesicle (substomatal vesicle), which in turn forms one or more infection hyphae.…”