A comparison of early molecular fertilization mechanisms in animals and flowering plants

Since the first description of the double fertilization process in flowering plants (angiosperms) 110 years ago (Nawaschin in Bull Acad Imp Sci St Petersburg 9:377–382, 1898), little progress has been made during the following 100 years to understand the underlying molecular mechanisms. This seems to be in strong contrast to our steadily increasing knowledge of single fertilization in animals, where a large number of key players and the corresponding molecular mechanisms have been unclosed since the mid-1970s. Are the identified fertilization mechanisms ubiquitously dispersed, occurring also in higher plants? The past few years have seen a number of discoveries indicating that general principles of fertilization mechanisms in animals and flowering plants are more conserved than previously thought. Here, we compare the development and morphology of animal and flowering plant gametes, discuss cell–cell communication events between gametes and gametophytes as well as their physical interaction and fusion during single and double fertilization, respectively.