Temporal changes in the RNA distribution between polysomes and postpolysomal ribonucleoprotein particles in tobacco male gametophyte

Growth of tobacco (Nicotiana tabacum L.) pollen tube is controlled by post- transcriptionally regulated protein synthesis. Stored mRNA was found to be present in the form of messenger ribonucleoprotein particles (mRNPs) in bot h maturing and germinating pollen. During pollen dehydration in the anthers content of mRNPs strongly increased during dissociation of polysomes sugge sting a transfer of mRNA liberated from polysomal structures into mRNP part icles. Pollen germination and initial pollen tube growth characterized by r apid reassociation of ribosomes was accompanied by decrease of mRNPs indica ting an involvement of mRNA of these particles in the formation of polysome s. Distribution of the particular mRNAs during the pollen activation precee ding tube growth suggests that other mechanisms along with pollen rehydrati on are engaged in this' process and that the continuous exploitation of sto red mRNPs during pollen tube growth is precisely regulated.