We studied the morphological changes of Saccharomyces cerevisiae ascospores during germination. Initiation of germination is followed by polarization of actin patches, maintaining their localization to the site of cell surface growth. Loss of polarisome components, Spa2p, Pea2p, Bud6p or Bni1p, results in depolarization of actin patches. Green fluorescent protein-fused polarisome components exhibit the polarized localization, implying that polarisome is involved in the polarized outgrowth during germination. At the late stage of germination, we found that actin patches temporally depolarize before bud emergence. The observation that loss of Cla4p extends the polarized growth period suggests that Cla4p is involved in the actin-depolization step. Actin polarization in the initial stage is accelerated by overexpression of Ras2p, whereas hyperpolarization is continuously observed by overexpression of Rho1p. Thus, yeast spore germination is a morphological event that is regulated by a number of factors implicated in mitotic bud morphogenesis.

Protoplasts isolated from tomato, wild tomato, barley and chrysanthemum were electrotransfected with tobacco mosaic virus (TMV) RNA under almost the same optimum electric conditions: five square DC pulses of 50 ~ts duration at 500 to 800 V/cm, with the protoplasts suspended at 2 x 105/ml in 0-5 M-mannitol containing 100 ktM-MgC12 and 10 to 20txg/ml TMV RNA. ELISAs of these transfected protoplasts showed that the yields and the growth curves of the virus were quite similar, indicating a lack of host specificity in the initially infected cells of these plants.