We all need guidance in life. And sperm cells are no exception to the rule. In plants, as in all living beings that depend on sex to multiply, a male gamete has to reach a female gamete in order to fuse with it. All sorts of mechanisms are used for this to occur. And plants are among the most imaginative organisms on the planet, simply because their mobility is so reduced. As such, they depend on forms of mobility that surround them: wind, bees, wild animals... And they have exploited this remarkably. At the molecular level, however, plants are far more mobile. An example is pollen tube elongation. In mouse-ear cress (Arabidopsis thaliana), for instance, once the pollen is ready to germinate, a bulge protrudes from its surface, elongates - and forms what is known as the pollen tube. Hordes of molecules are involved in pollen tube elongation. But you also need something which can actually guide the tube towards the ovule. And its name is protein HAPLESS 2, or HAP2.
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