Inhibition of RNA and protein synthesis in pollen tube development of Pinus bungeana by actinomycin D and cycloheximide

The effects of actinomycin D and cycloheximide on RNA and protein synthesis were investigated during pollen tube development of Pinus bungeana. RNA and protein contents, protein expression patterns, cell wall components and ultrastructural changes of pollen tubes were studied using spectrophotometry, SDS-PAGE electrophoresis, Fourier transformed infrared (FTIR) microspectroscopy and transmission electron microscopy (TEM). Pollen grains germinated in the presence of actinomycin D, but tube elongation and RNA synthesis were inhibited. By contrast, cycloheximide inhibited pollen germination and protein synthesis, induced abnormal tube morphology, and retarded the tube growth rate. SDS-PAGE analysis showed that protein expression patterns changed distinctly, with some proteins being specific for each phase. FTIR microspectroscopy established significant changes in the chemical composition of pollen tube walls. TEM analysis revealed the inhibitors caused disintegration of organelles involved in the secretory system. These results suggested RNA necessary for pollen germination and early tube growth were present already in the pollen grains before germination, while the initiation of germination and the maintenance of pollen tube elongation depended on continuous protein synthesis.