The plants and the bees and the STDs

Linda Jewell
29 April 2015

Above: Main parts of as mature flower, showing the plant’s reproductive organs (Wikimedia Commons/Mariana Ruiz)

Did you know? Just like animals, plants have an immune system. When a disease-causing pathogen is detected, plants can mount their defences to try and fend off the attacker!Sexually transmitted infections (STIs), also commonly called sexually transmitted diseases (STDs), are no joke. Sexual contact between two people can spread dangerous infections with serious consequences. The idea of a plant catching an STI may sound silly, but diseases that occur on a plant’s reproductive organs or as a direct result of spreading pollen from one plant to another could be considered the plant equivalent of an STI.

Generally speaking, it is possible for plants to catch many different kinds of diseases. For instance, you might have noticed that maple leaves often have big, scabby black spots on them that are about the size of a quarter. These spots are a symptom of tar spot, a fungal disease. Another example of plant disease would be when bacteria clog up vascular tissues, which are the “veins” that transport water and sugars throughout a plant. In fact, there are thousands of microorganisms and viruses that can attack every part of a plant, so it shouldn’t be such a surprise that a plant’s sexual organs can also host an infection.

Of course, plant sex is a little different from animal sex. Flowers contain the sexual organs of the plants that produce them. Make sure you remind your date of this next Valentine’s Day! Pollen is transferred by the wind or by pollinators onto the stigma, the female part of a flower. Sperm cells carried within the pollen grain can then be transferred into the flower’s ovary, where fertilization occurs.

Some plant STIs affect the development of a flower’s reproductive parts. For example, when spores of the fungus Ustilago violacea land on their wildflower hosts, they germinate and grow through the plants' tissues until they reach a developing flower bud. From there, the fungus infects the developing anther.

Did you know? The fungus Ustilago maydis attacks corn and causes the kernels to become hugely swollen and turn black. This diseased corn is eaten as a delicacy called huitlacoche!Instead of producing pollen, the anther of an infected plant swells up and turns black before releasing millions of fungal spores. In plants that make separate female and male flowers, if the fungus finds itself in a female flower (which wouldn’t normally form an anther at all), it can alter the plant’s development and force the female flower to produce a strange, rudimentary stamen so that the fungus can proceed with its normal infection process!

If an STI that can force a female flower to change its sex isn’t strange enough, how about an STI that can jump the 1.5 billion year evolutionary gap between the plant kingdom and the animal kingdom? Despite its name, tobacco ringspot virus (TRSV) doesn’t just affect tobacco. It also causes big problems for many other plants, including cucumbers, soybeans, and other important food crops. These plants can become infected when the virus is spread by a well-meaning visitor: bees! If bees unwittingly pick up pollen from a plant that is infected with TRSV, the virus can hitch a ride on the pollen and spread to a healthy plant.

That’s bad news not only for plants, but also for the bees. Researchers have found evidence that TRSV can actually reproduce inside bees, and bee colonies with higher levels of TRSV also have higher levels of other bee viruses and are more likely to suffer a population collapse when compared to bee colonies without the virus. This doesn’t mean that TRSV directly causes bee colonies to collapse, but it probably makes a bad situation even worse for colonies that are already struggling.

Did you know? The fungus Claviceps purpurea attacks plants’ anthers and produces powerful psychoactive compounds, including lysergic acid (LSD).This research suggests that the virus might have found a way to hop hosts from a plant to an animal, which is a pretty impressive evolutionary feat! Although it’s unusual, there are a few other groups of viruses known to infect both plants and insects. For example, flock house virus can actually multiply in plants, insects, or fungi!

Around the world, bee numbers have been dropping dramatically, and although many possible causes have been proposed there isn’t yet a clear cause or solution. The newly-discovered link between TRSV and honeybees probably isn’t the cause of this mystery, but the unexpected relationship between bees and a plant STI demonstrates just how complicated ecological relationships can be.

Learn more!

What is Plant Pathology? (2014)
Canadian Phytopathological Society

Introduction to phytopathology, the study of disease in plants.

Suspicious Virus Makes Rare Cross-Kingdom Leap From Plants to Honeybees (2014)
Jennifer Frazer, Scientific American Blogs

Discussion of tobacco ringspot virus and its ability to jump from plants to animals.

Tomato Anatomy: Fertilization (1996)
Thomas L. Rost, University of California, Davis

Description of the reproductive cycle in tomato plants.

Linda Jewell

For my BSc, I studied biopharmaceutical sciences with a concentration in medicinal chemistry at the University of Ottawa, and I completed an honours project investigating the role of a particular group of receptors during early development in zebrafish! For my MSc, also at the U of O, I extracted and made synthetic mimics of chemical compounds from plants. My PhD research centered around two very closely related fungi that cause plant disease. Right now I am in Sapporo, Japan, working as a postdoctoral fellow and continuing some work with this low-temperature fungus to try to improve our understanding of how this fungus interacts with its plant victims.

My research interests are all over the map because science is fascinating, and I feel very lucky that I have been able to explore so many different areas!

When I'm not in the lab, I like reading, knitting, playing video games, running, and snowboarding.

Comments are closed.


Avatar  Mouthana Alhabib

Hi Mrs. Linda, I appreciate your work and experience of biopharmaceutical. I am really happy that you are interested in my field also. I am mycologist mainly in medicinal fungi, and I have been achieved researches and pilot plan in Huitlacoche Ustilago maydis and Ustilago esculenta and more medicinal mushrooms. I find and recorded new strain as immunomodelator. I hope that I can hear from you. Best regards, Senior Scientific Researcher

Avatar  James

Hello Linda,

I was searching for some articles about Huitlacoche today and I came across your page:

I noticed that you linked to one of my favorite articles --

You can find it inside this page and search for the Anchor text: huitlacoche

But the page doesn't exist now.

Just wanted to give you a heads up that I created a similar. It's like "Corn Smut Delicacy Huitlacoche Is Good For You",
but more thorough and up to date:

Might be worth a mention on your page.

Either way, keep up the awesome work!