Broccoli and cabbage mixture…a discovery that paves the way for the emergence of entirely new crops sciences

Imagine millions of pollen grains in the air, coming from dozens of plant species at the same time, and yet each flower knows exactly which pollen it allows to pollinate it and which it rejects.

This amazing ability was one of the mysteries of botany, however study A new study published in the prestigious journal Science brings us a big step closer to understanding it.

According to the study, many flowering plants have developed a system called “self-incompatibility,” meaning that the plant does not allow its own pollen, or the pollen of its close relatives, to pollinate it. The goal of this is to avoid pollination of relatives and the resulting weakness in offspring and lack of diversity.

But another important question remains: What about pollen coming from other species in the same plant family?

A very special family

Here comes the role of an international research team led by Chinese Professor Alice Cheung, who specializes in biochemistry and molecular biology, and they chose the Brassicaceae family as a model for the study.

This family includes plants we all know, such as cabbage, broccoli, kale, kale, canola (used in the production of edible oil), and other important vegetables.

Scientists here are interested in another type of rejection system called “species incompatibility,” that is, the system that prevents the pollen of one species from pollinating another species within the same family.

The problem is that the mechanism of incompatibility between species at the molecular level was until recently almost a black box. We know that it exists, but we do not know the details of the “language” by which flowers communicate with foreign pollen to say to them, “You are rejected.”

Incompatibility

In contrast, the self-incompatibility system is known in relatively detail, especially in Brassicaceae. Here came the team’s idea: What if the plant used some of the same tools that it uses to reject its own pollen, to reject the pollen of other species as well?

The new study revealed that plants from the Brassicaceae family use an important protein called SRK, which was previously known to be the main key in the self-incompatibility system in Brassicaceae plants.

SRK is located at the tip of the stigma (the part of the flower that receives pollen). This protein recognizes a specific chemical signal on the surface of pollen grains, a signal the researchers call “SEPs,” that is present in the pollen of other Brassica species that the flower wants to reject.

When SRK recognizes this signal, the matter does not stop there. This “deal” calls to the scene another enzyme known in the plant world, “Feronia”, which is a protein that Professor Cheung and her Chinese colleague, Professor Xiaohong Duan, have been studying for years.

The interaction between Feronia, the SRK dimer, and the signal ignites a chemical cascade inside the stigma cells, producing a highly reactive substance that acts as a defensive barrier, stopping pollen tube germination and preventing it from advancing into the ovary, thus aborting the pollination process before it begins.

Why is this important?

Besides solving an important part of the puzzle of how plants distinguish between an acceptable pollen and a rejected one, the researchers are also proposing a new breeding strategy to bypass these barriers in some cases.

The idea is that understanding the proteins and molecules responsible for rejection could help plant breeders manipulate these signals (such as modifying SRK or vironia) so that plants occasionally allow pollen from more distant relatives, opening the door to new hybridizations in important cruciferous crops such as cabbage and broccoli.

Thus, the study not only reveals the language of “acceptance and rejection” between flowers and pollen, but also hints at practical tools that agriculture can use in the future to develop more diverse and powerful crops, in a world where pressure on food production increases with climate change and the increase in population. Science here not only explains how plants protect themselves from “unwanted marriage,” but also attempts to put this knowledge into the service of our food today and tomorrow.