# ‘Roly-poly toy’ motion during pollen exudation promotes rapid pollen adhesion in rice

## TL;DR

Rice pollen grains rock like a 'Roly-poly toy' on sticky exudates, helping them stick quickly to the stigma for efficient self-pollination.

## Contribution

The study reveals a novel 'Roly-poly toy'-like motion of rice pollen grains during exudation that promotes rapid adhesion.

## Key findings

- Pollen grains exhibit rocking motion on exudates to enhance adhesion.
- Exudates contain high sugar, fatty acids, and redox-related metabolites.
- The motion aids optimal positioning for rapid self-pollination.

## Abstract

In angiosperm, successful pollen adhesion and hydration on the stigma are essential for pollen germination and tube elongation. Self-pollinated grass plants, such as rice, exhibit viscous ‘pollen exudation’ prior to adhesion; however, its cellular dynamics, including their chemical composition, remain unknown. Here, we revisit pollen exudation in rice to find that pollen grains showed ‘Roly-poly toy’-like rocking motion on the exudates to lead pollen adhesion. Single-cell metabolomics revealed that exudates were composed of high content of sugar together with fatty acids and redox-related metabolites, different from mature pollen grains and stigma cells. And hence, these solutes might participate in osmotic and molecular signaling in stigmatic apoplast, increasing the fluid viscosity. Taken together, it is concluded that the unique behaviour observed in rice pollen grains might play a crucial role on optimal self-positioning and adhesion prior to pollen germination, resulting in the rapid self-pollination.

A study on rice pollination using single-cell metabolomics and microscopy reports a discovery such that pollen grains attached show “Roly-poly toy”-like physical motion subsequently after exudation, leading to pollen adhesion and germination to facilitate rapid pollination.