Reduction of Leucine Efflux and Protein Release from Tobacco Pollen Tubes in Culture by Actinomycin D in the Absence of Calcium

Abstract

In a pollen medium lacking calcium, actinomycin D (AMD) increases pollen tube labelling with exogenous 14 C-leucine. This increase is greater when pollen tubes are preloaded with unlabelled leucine and is caused by a higher retention of leucine taken up. AMD also reduces the release of pollen tube proteins into the medium. The extent of this effect grows only slightly with the rise of AMD concentration from 0.5 to 10 µg ml -1 and is very low or none when calcium is present. Calcium itself decreases the release of proteins from pollen tubes. Unlike the increase of leucine retention, the decrease of protein release by AMD is not evident before the beginning of AMD-induced inhibition of pollen tube growth.