Bean rust fungus
Laser scanning confocal microscopy
Springer Online Journal Archives 1860-2000
Summary Formation of appressoria inUromyces appendiculatus is triggered by external physical features of host stomata as well as artifical surfaces bearing inductive topographies. Microtubule and F-actin microfilament cytoskeletons were examined for their involvement in the process of appressorium formation in this fungus, using laser scanning confocal and electron microscopy. In germlings not stimulated to form appressoria the microtubule and microfilament cytoskeletons were organized as filaments mostly oriented parallel to the longitudinal axis of the cell. Following contact of the germling apex with an inductive topographical signal, e.g., 0.5 μm high ridge, the microtubules and F-actin filaments in the cell apex nearest the substrate appeared randomly oriented. Microtubules farther from the substrate remained oriented parallel to the longitudinal axis of the cell. In later stages of appressorium development, many cytoskeletal elements became oriented parallel to the inductive ridge, especially near the substrate. In regions farther from the substrate in these same cells, the microtubules and microfilaments were arranged in a reticulate pattern. Changes in the distribution and organization of the microtubule and F-actin microfilament cytoskeletons reflect a change in cell function following signal reception for appressorium. The reorientation of the cytoskeleton likely dictates the change in cell morphology.
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