Close contact: role of the extracellular matrix in cell adhesion and separation during plant development and reproduction.

In plant organisms, cells have two ways of being connected to each other. They are either adhering to the same neighbouring cells since mitosis or they enter in contact de novo with a new cell and adhered themselves. These different intercellular interactions have multiple roles depending on the location of the cell studied or the stage of the plant's life cycle. Intercellular adhesion, for example, helps in maintaining tissue integrity, controlling cell shape, and even plays a role in defense. De novo cell adhesion, on the other hand, occurs at specific times in the life of the plant, particularly at three stages: cell elongation of fibres and their adhesion to each other, and during sexual plant reproduction: adhesion of the pollen grain to the stigma and adhesion of the pollen tube to the transmitting tract cells in the style and ovary. It is already well-known that the cell wall regulates cellular interactions and governs intercellular and de novo cell adhesion but only few studies have focused specifically on the molecules involved in the second mechanisms. In this review, we summarize current knowledge on the polymers involved in cell adhesion and separation in sporophyte tissues and male gametophytes on/in the female sporophyte.