The Chinese cabbage has a ‘superqueer’ sex life

The pollinator radar of Hanneke Suijkerbuijk (35) is properly adjusted. She just told me that since she started her PhD, she has become increasingly quick to spot insects – a small movement in the corner of her eye, a soft buzz, that’s all it takes. And now, during the photo session amid the autumn flowers on the Wageningen university campus, it happened. “Blind bees,” she says immediately. And indeed, after looking closely, some yellow-black striped hoverflies can be seen among the yellow: the blind bee, despite its name, turns out not to be a bee.

A little further away, in the garden and greenhouse next to the Radix building, Suijkerbuijk has looked at flying insects countless times in recent years: which species were attracted to which plants and how long they stayed there. “For my PhD, I studied how insect damage can influence the pollination of plants, and in particular that of Chinese cabbage – a cultivated variety of rapeseed, Brassica rapa. That is an annual plant so it blooms quickly, which is useful if you only have four years for your research.” She discovered that all that gnawing can have very different consequences. “Pollinators can behave differently on a plant with feeding marks, but the plant itself can also react differently. For example, by self-pollinating more quickly.”

Like many other plants, the sex life of Chinese cabbage is “super queer,” says Suijkerbuijk. “They have very different options for producing offspring, with both eggs and pollen, they can fertilize themselves or cross with other plants…” However, most plants have one preferred variant. “In general, cross-pollination benefits one species, because it reduces the risk of inbreeding. But if your time as a plant is running out because of food consumption, and you have the pollen and eggs at your disposal to pollinate yourself, wouldn’t you still opt for self-pollination under those stressful circumstances?”

Interesting for organic farming

The answer to this lies in the different genotypes, Suijkerbuijk discovered. “Depending on their precise genetic composition, Brassica plants turned out to use different strategies. For example, one genotype produces substantially more seeds after being eaten by insects, while another genotype mainly suffers adverse consequences in terms of reproduction, or hardly responds at all. Such discoveries are interesting for agricultural breeding: you need much fewer pesticides if you have plants that eat well. respond.”

And then there is the interaction with pollinators: this also appears to be dependent on the plant genes. “A genotype that still produces a lot of pollen under stress will attract more pollinators than a genotype that does not.” And if a plant has many flowers, the pollinator is more likely to visit another flower of the same plant, increasing the chance of self-pollination – with the insect as a facilitator.

“What I liked about this research was that there was no clear answer, because you have all those genotypes. A strategy that is successful one year does not necessarily have to be successful the next. That is why it is useful at group level if all those variants are present. You also see this in people: our society is not one-size-fits-all.”

Excursion into insect brains

Suijkerbuijk finds the interaction between organisms fascinating. “Interactions are the common thread in my career: between plants and insects, between people – before my PhD I worked in the communications department here at the university for three years. I was not the typical biologist who, as a 5-year-old, fished in the ditch with a landing net, I have always found behavior especially interesting. That is why I also made a trip to cognitive neuroscience during my studies, in Nijmegen. There – and later also in Wageningen, When I got back – I looked at insect brains: I wanted to investigate how a specific virus affected the behavior of a moth called Spodoptera exuigathe Florida owl. Under the influence of that virus, that caterpillar climbs all the way to the top of a plant and dies there.” She points to the caterpillar cuddly toy she is carrying. “This is Spodoptera exuigamade by a former colleague of mine.”

Initially, Suijkerbuijk was afraid that a PhD program might be too monotonous. “But luckily I was allowed to write my own proposal, with many types of research: in the field, in the lab, in the greenhouse, behind the microscope… That’s why those four years flew by.”

She has now even started a postdoc program at Wageningen University, also with the group plant-insect interactions. “It is such a broad subject that I can still express my curiosity. Now I want to look more at the evolutionary side of plant defense. A plant that defends itself very well against being eaten, for example by developing smaller flowers, may therefore also become less attractive to pollinators. Therefore, excessively avoidant behavior is not necessarily beneficial.”

In any case, Suijkerbuijk will not quickly get tired of insects. “You can’t look at pollinators for long without appreciating them. What I like about bumblebees, for example, is that they really seem to have different characters – one much more active than the other. On hot days, with that oppressive weather, I even saw some bumblebees fall asleep in the flowers they visited.”

One beginner’s tip for those who want to develop a pollinator radar themselves: keep an eye out for purple flowers. “These are very popular with bumblebees. With purple vegetation you are almost certain that you will be successful.”

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