According to a CNRS communication dated September 22, 2025, following a scientific publication in PLOS Computational Biology co-authored by Lucie Riglet, Christophe Godin, and Isabelle Fobis-Loisy, researchers at the RDP, ENS de Lyon, together with Catherine Quilliet and Karin John from LIPhy, Université Grenoble Alpes.
At the center of the Arabidopsis thaliana flower, the pistil, composed of hundreds of papillae and an ovary containing the ovules, is surrounded by stamens that release pollen grains carrying the male gametes. In an article published in PLOS Computational Biology, by combining theory and experiment, scientists reveal how the male gametes are guided toward the ovules from the very beginning of their journey along the surface of the female reproductive organ.
The Flower: Key to the Reproductive Success of Plants
Today, flowering plants represent more than 90% of the plant species around us. Their success is due in part to a major evolutionary innovation that optimized and secured reproduction: the flower.
There is an extraordinary diversity of flowers, yet they all share one essential feature: they centralize the reproductive organs and protect the gametes within specialized structures. Most flowers are hermaphroditic, meaning they contain both female (pistil) and male (stamens) reproductive organs (Figure A).
Looking more closely at the pistil, one finds at its tip a multitude of almost cylindrical cells known as stigmatic papillae, and lower down, a slightly swollen part containing the ovules (Figure B). The stamens, for their part, bear a sac-like structure at their tip which, when the flower opens, releases its contents: the pollen grains that contain the male gametes (Figure B).
The ovules, enclosed within the pistil, and the male gametes, enclosed within the pollen grains, are therefore well protected. The trade-off, however, is that when hundreds of pollen grains land on the tip of the pistil, on the papillae, the male gametes are still far from their destination. They cannot reach the ovules directly, and unlike sperm cells, they are unable to move on their own!
This is where the pollen tube comes into play
In Arabidopsis thaliana, a model plant widely used in research, the pollen grain forms a tube upon contact with a papilla. The male gametes then migrate to the tip of this tube, which elongates through the papilla and into the ovary to reach the ovules. Once a tube penetrates an ovule, its tip ruptures, releasing the male gametes (Figure C). The goal has been achieved: the male gametes can now fuse with the female gametes to give rise to an embryo - the origin of the future seed.
Find out more on the CNRS website (FR)
Reference:
Geometric and mechanical guidance: Role of stigmatic epidermis in early pollen tube pathfinding in arabidopsis. Riglet L, Quilliet C, Godin C, John K, Fobis-Loisy I. Plos Computational Biology, 27 mai 2025, DOI: https://doi.org/10.1371/journal.pcbi.1013077
