Cytopathology of Developing Anthers and Pollen Mother Cells from Lettuce Plants Infected by Lettuce Mosaic Potyvirus

Ultrastructural studies of developing anthers from young flowers of lettuce (Lactuca sativa L.) infected with lettuce mosaic potyvirus (LMV) revealed infection in the pollen mother cells of one of three plants. Within the infected pollen mother cells, structures reminiscent of bundles and partly formed pinwheel inclusions were observed. Immunogold labelling showed that particles of LMV were associated with these structures. Neither large aggregates of LMV particles nor complete pinwheei inclusions were observed in pollen mother cells. Infection of pollen mother cells was consistently correlated with infection of the adjacent tapetal cell layer. Pollen mother cells of two other LMV-infected plants were not infected. This study supports the hypothesis that early invasion of the floral meristem is necessary for virus infection of mature pollen grains.