The two male gametes share equal ability to fertilize the egg cell in Arabidopsis thaliana

SummaryThe seed of a flowering plant develops from an ovule containing two distinct female gametes — the egg cell and the central cell — that are fertilized by a pair of non-motile sperm cells conveyed by the pollen tube. With a few exceptions [1], the two sperm cells, derived from a symmetrical mitosis, are isomorphic and seem to express a similar gene repertoire [2]. Since the discovery of double fertilization in flowering plants at the end of the 19th century, it has been a long standing question whether the two sperm cells are functionally equivalent, that is, whether they are capable of fertilizing the egg cell and the central cell in equal measure