Masaru Nakayasu
During double fertilization in angiosperms, sperm nuclear fusions take place shortly after sperm cells fuse with each of the female gametes (egg and central cell). Maruyama et al. (pp. 29-40) found that depletions of BiP1 and BiP2, two Hsp70 proteins in the endoplasmic reticulum of Arabidopsis thaliana, cause nuclear fusion defects in the egg cell and the central cell. A time-lapse confocal microscopy series revealed that nuclear fusion following chromosomal decondensation of the sperm nucleus plays pivotal roles in endosperm development, which is necessary for subsequent seed formation.