RNA AND PROTEIN-SYNTHESIS IN SPERM CELLS ISOLATED FROM ZEA-MAYS L POLLEN

Sperm cells are thought to be quiescent in pollen and activated upon pollen germination. To test this hypothesis, protein, RNA and DNA synthesis were assessed in Zea mays sperm cells at different times after isolation from pollen. Protein synthesis changed with time; while some proteins were found to be constitutive in both 0 and 24 h cells, others were synthesized and some disappeared. Overall, the number of proteins detected at 24 h doubled compared with freshly isolated cells. Incorporation of [H-3]leucine in 24 h cells was about 50 times that in freshly isolated cells, and that of [5, 6-H-3]uridine, about 7 times. Very low incorporation of [6-H-3]thymidine into the cells was detected; there was no difference between freshly isolated and 24 h cells. It is possible that the differences in synthetic activity between freshly isolated and 24-h-old cells might correspond to sperm cell activation during pollen tube growth. If so, these metabolic changes may play an important role in fertilization.