Protein Changes in Tobacco Pollen Culture; a Newly Synthesized Protein Related to Pollen Tube Growth

Abstract

Pollen of Nicotiana tabacum L. was grown for various intervals of up to 48 h. At pH optimum of culture medium enabling linear tube growth, the rate of protein synthesis was relatively constant and the uptake of external leucine declined only slightly. In addition to some changes in proportions of individual proteins separated by SDS-PAGE, the growth of pollen tubes was associated with the appearance of a novel non-covalently bound protein with apparent molecular mass of 65 kD. Its de novo synthesis was already detected during the first hours of germination but not in non-germinating immature pollen. At optimal pH, the amount of this protein increased proportionally to the length of pollen tubes throughout 48 h, while in non-buffered medium its increase ceased after 8 h, before growth came to a stop due to external pH decrease. In comparison with other pollen proteins, the synthesis of the new protein is much greater and seems to be involved in tube wall formation.