Yoji Doi

Intracellular appearance of Penicillium chrysogenum virus.

Abstract An electron microscopic study of intracellular Penicillium chrysogenum virus showed virus particles with a dense core distributed as individuals or aggregates in cytoplasm and/or in vacuoles of mycelial cells. In cytoplasm the virus particles were often near, but not in, the nucleus. Electron-dense regions of granular appearance enclosed more complete virus particles in some cells. Lipid bodies, vacuoles, and membranous structures were often prominent in infected cells. Sometimes cylindrical arrays of virus particles occurred in vacuoles and also in degenerated cells. Aberrations consisting of various degrees of degeneration or disappearance of cytoplasm and cellular organelles were often observed in aged cells with large quantities of virus. The virus particles sometimes released fibrous material forming networks from their core region.

Conidiomatal development of Pestalotiopsis guepinii and P. neglecta on leaves of Gardenia jasminoides

This study has clarified the conidiomatal development ofPestalotiopsis guepinii andP. neglecta on leaves ofGardenia jasminoides. Acervuli ofP. guepinii andP. neglecta developed in a similar manner, in two stages. In the first stage, cells aggregated, the central cell of the aggregates gradually disappeared, and the cells of inner layer produced numerous conidia. This conidioma was pycnidium-like in appearance, and in some cases ceased development at this stage. In the second stage, the upper layer of the pycnidium-like structure broke open, forming an acervular conidioma.

Conidial adhesion and germination of Pestalotiopsis neglecta

The adhesion of conidia of Pestalotiopsis neglecta occurs in four stages in a specific manner which allows the first cell most likely to germinate to become firmly attached its substrate while leaving the other two fertile cells free to be dispersed further, thereby increasing the chance of further successful infections. The first stage of adhesion involves the mucilaginous coating acquired from the conidial matrix and appears weak. The second stage of adhesion is also relatively weak and occurs at the bases of the pedicel. The third stage occurs with the release of a fibrillar adhesive substance from along the length of the pedicel to the top of the basal cell and at times a lesser amount of fibrillar material is released from the apical appendages. The fourth stage involves the release of fibrillar material at the point of germtube emergence. The third and fourth stages provide strong attachment.

Adaptations of potential ecological significance to Pestalotiopsis neglecta.

A germination inhibitor in the spore matrix of Pestalotiopsis neglecta was strongly inhibitory to other mitosporic fungi, especially coelomycetes. Germination of conidia of P. neglecta was enhanced by an exogenous source of certain carbohydrates, especially pectin but also some sugars. Light was not important for germination or growth, and was not essential for reproduction, although the number of acervuli trebled when light intensity was increased from 210 μmol m−2 s−1 to 300 μmol m−2 s−1. The possible significance of these adaptations in the ecology of P. neglecta is discussed.