Figure. Two-Step Pollination Mechanism in Self-Pollinating Brassicaceae Plants

Under the support of the National Natural Science Foundation of China (Grant Numbers: 32388101, 32122014, 32070854), a research team led by Professor Lijia Qu and Research fellow Sheng Zhong from Peking University has identified a conserved "two-step pollination" mechanism in self-pollinating Brassicaceae plants. The findings, titled “A two-step self-pollination mechanism maximizes fertility in Brassicaceae” were published online in Cell on April 14, 2025. The paper is available at: http://www.cell.com/cell/fulltext/S0092-8674(25)00294-6.

Pollination, the transfer of pollen from dehiscent anthers to the stigma, marks the initial step of sexual reproduction in angiosperms. It is also the least efficient and most uncertain phase. Plants primarily adopt two pollination strategies: cross-pollination (enhancing genetic diversity) and self-pollination (ensuring reproductive stability in fluctuating environments, e.g., pollinator scarcity). Approximately 10-15% of angiosperms are self-pollinating, including major crops like rice, wheat, soybeans, peanuts, and tomatoes. Self-pollinating plants typically exhibit "selfing syndrome," such as reduced flower size and lower pollen-to-ovule ratios. However, their exposed stamens make pollen vulnerable to environmental stressors, meaning successful fertilization heavily relies on pollen quantity and quality.

The team discovered a novel "two-step pollination" phenomenon in self-pollinating Brassicaceae species, including the model plant Arabidopsis. In the first step, pollination occurs within unopened flowers as anthers contact the stigma’s lateral edges. Petals then reopen 6-7 hours after initial opening, allowing elongated stamens to recontact the stigma’s central region for a second pollination. This mechanism significantly increases effective pollination area and total pollen load.

Further studies revealed that under pollen-limited or stressful conditions, plants relying solely on the first pollination step suffered severe fertility loss. The spatiotemporal separation between the two steps ensures that the second pollination compensates by boosting total pollen delivery, thereby enhancing fertilization efficiency. This work elucidates how the two-step mechanism maximizes fertility under adverse conditions and offers new strategies for improving crop yield stability through controlled pollination. The research provides critical insights into plant reproductive adaptation and opens avenues for optimizing agricultural productivity in challenging environments.