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 p ollen germination. To test this hypothesis, protein, RNA and DNA synth esis were assessed in Zea mays sperm cells at different times after is olation from pollen. Protein synthesis changed with time; while some p roteins were found to be constitutive in both 0 and 24 h cells, others were synthesized and some disappeared. Overall, the number of protein s detected at 24 h doubled compared with freshly isolated cells. Incor poration of [H-3]leucine in 24 h cells was about 50 times that in fres hly 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; th ere was no difference between freshly isolated and 24 h cells. It is p ossible that the differences in synthetic activity between freshly iso lated and 24-h-old cells might correspond to sperm cell activation dur ing pollen tube growth. If so, these metabolic changes may play an imp ortant role in fertilization.