Fig. 7. Fate of the single sperm cell during msi1 pollen tube growth. (A) Percentage of pollen tubes transporting a single sperm cell from a msi1-1/+ Arabidopsis plant at different time points after pollen germination in vitro. Errors bars correspond to standard errors calculated on the basis of three replicates of 100 pollen grains. (B-D) Transport of sperm cells marked with HTR10-mRFP in pollen tube germinated in vitro from wild-type (B) and msi1/+ (C,D) plants. (B) At 6 hours after germination, wild-type pollen tubes transport two sperm cells (two fluorescent red dots). (C) By contrast, at 6 hours a msi1 pollen tube transports a single sperm cell. (D) At 7 hours after germination the msi1 single gamete had divided into two sperm cells. (B,C,D) Superimposed DIC images of the pollen tube with the mRFP1 fluorescence signal identifying the sperm cells. Scale bars: 20 µm.