Featured Book: Pioneering Women in Plant Pathology
In this video, Sophien Kamoun briefly introduces the inspiring book “Pioneering Women in Plant Pathology”, published by the American Phytopathological Society and edited by Jean Ristaino. Support plant pathology and get your own copy at the APSnet Store.
Hello, I’m Sophien Kamoun. I’m a plant pathologist at The Sainsbury Lab in Norwich in the UK. Today, rather than talking about how plants get sick and how pathogens infect plants, I’m going to tell you about a book I read and found to be really inspiring.
This book, Pioneering Women in Plant Pathology, was edited by my colleague Jean Ristaino, a professor of plant pathology at North Carolina State University. The book is organized in a series of 27 chapters, each focused on a woman scientist who was an active plant pathologist and contributed to our field.
As described in the moving dedication, the motivation for writing this book is to chronicle the life and work of all these women who contributed to the science. Often their contributions were not properly documented or recognized. Now, Jean and all our colleagues who contributed the various chapters are recognizing this pioneering work.
Now, let me tell you the stories of three of these inspiring women plant pathologists.
Johanna ‘Hans’ Westerdijk: Take a bow to this pioneering Dutch plant pathologist
The first woman I want to tell you about will not come as a surprise to those of you who know the field of plant pathology. She’s Johanna Westerdijk, a Dutch plant pathologist who essentially started the field of mycology in the Netherlands. She founded the Centraalbureau voor Schimmelcultures (CBS) culture collection, which still exists and morphed into an institute that was re-named the Westerdijk Fungal Biodiversity Institute in 2017. She also founded the Dutch Mycological Society and was the first female professor in the Netherlands.
Johanna, or Hans as she’s known, was famous as a formidable lady who supervised many scientists and contributed to research in many ways, notably on studying the infamous Dutch elm disease first described by her doctoral student Bea Schwarz in 1921. She was at the University of Utrecht and was appointed professor in 1917, and if you happen to be at the University of Utrecht Auditorium (Aula) attending one of those public events when PhD students defend and then celebrate their theses, you will note her portrait there. You can see it there on the bottom left of the series of portraits of famous professors, the only lady on that wall, I think. Now look closer — do you see that small door, just below her portrait? When professors exit the room through that door, they have to bow to Johanna Westerdijk. I think that’s a very touching thing they did at the University of Utrecht.
Now, as I said, Johanna Westerdijk would not surprise you, but the next one may surprise many of you.
Rosalind Franklin: From Photograph 51 to TMV
Those of you who know about biology definitely know about Rosalind Franklin. She is of course famous for having contributed immensely to the discovery of the structure of DNA through her x-ray crystallography work. In particular, her famous Photograph 51 was even displayed in West End plays. My team and I were in London five years ago to watch the play at the Noël Coward Theatre where Nicole Kidman portrayed Rosalind Franklin — an amazing and unforgettable day.
What is less well known is that towards the end of her career, Rosalind Franklin worked on Tobacco mosaic virus — TMV, as we call it — for about four years and contributed to understanding the structure of this virus. The image portrayed here is from her work. Sadly, that was interrupted by her untimely death from cancer. But her contributions to plant pathology are important, so we have adopted her as one of our famous female plant pathologists.
Eva Sansome: Oomycete cytogenetics in the kitchen
Now, I’d like to focus on Eva Sansome, because her story is very touching and her work is closest to my field of research. Eva started in the 1930s studying plant biology — at that time, nothing to do with plant pathogens. Her expertise was in cytogenetics, which was really budding at the time. That’s the field where you study DNA and chromosomes using cell biology techniques. Think of this field as the precursor of modern day genomics. This is some of her early work on pea, Pisum sativum, dating back to the 1930s.
In this photo from the 1960s, you can see the diminutive Eva on the left side. But way before that, she moved to Cold Spring Harbor Laboratory during World War II, and here is a 1942 photo of her at Cold Spring Harbor with the legendary Salvador Luria, who won a Nobel Prize in Physiology or Medicine and is famous for his contributions to microbiology, particularly understanding bacteria and bacteriophages and for the birth, essentially, of the field of molecular biology. His 1943 fluctuation test, also known as the Luria–Delbrück experiment, is one of the most ingenious and influential experiments from those early days of genetics — it demonstrated that mutations arise independently of the selective pressure that is applied.
During her stay at Cold Spring Harbor, Eva discovered mycology. She was mentored by a Russian scientist who was a mycologist. He taught her all the mycology methods, and apparently she got hooked. She went back to UK, and went on to have a very rich life living, teaching and working in Africa with her husband, who happened to be a botanist. Throughout those years she followed up on her work at Cold Spring Harbor by studying a group of microbes known as oomycetes. These are not strictly speaking fungi but at the time they were lumped together with the fungi. Eva’s work would go a long way in showing that they have truly distinct genetic features compared to the fungi.
Oomycetes include a very famous pathogen, perhaps the most famous plant pathogen of all, Phytophthora infestans. ‘Phytophthora’ means plant killer in Greek, and Phytophthora infestans is the agent of the potato blight, which triggered the Irish potato famine in the 1840s. You can see from this photo that when potatoes are susceptible and infected by this pathogen, they’re totally destroyed by Phytophthora, the plant killer.
We now know that oomycetes like Phytophthora are not fungi. They look like fungi superficially, but from an evolutionary point, and once we understand their biology, we realize that similarity to fungi is quite superficial and doesn’t reflect any evolutionary relationship, as oomycetes are not closely related to fungi.
Well, at the time when Eva was doing her work, that was not fully appreciated. So back in the 1970s, there was a long debate about the genetic material of oomycetes. Many scientists, notably scientists in the US, thought that oomycetes were haploid, just like fungi. They were biased by their perspective that these organisms are fungi.
What does it mean to be haploid? Haploid organisms have a single copy of every gene in their cells. But many organisms, including animals and humans and so on, are diploid. They have two copies of every gene, every chromosome, in their cells. One comes from one parent, and the second copy comes from the other parent.
What Eva discovered was that oomycetes like Phytophthora are diploid. They’re not like the majority of fungi; they’re not haploid. That was quite a debate at the time, in the 70s. It was controversial. But her work was really beautiful. Using the methods of cytogenetics she polished since the 1930s, she showed clearly that in the egg cells (or oospores) of Phytophthora, in particular Phytophthora infestans, the potato blight agent, you can clearly see that this organism is very likely to be diploid. It really took until the 1980s before this view was widely accepted. Also the fact that oomycetes are really distinct from the fungi really took hold only in the 1980s when genomic sequences would precisely place the oomycetes as a type of heterokont algae unrelated to the fungi in the tree of life.
A little side story about Eva. When she came back with her husband from Africa, they essentially retired in Norfolk, more precisely in the quiet village of Diss, not far from Norwich where my lab is located. Her most famous work actually comes out of experiments she conducted in her kitchen lab. Indeed, you can see that in her paper in Nature: her address is actually her home address in Diss, Norfolk.
Whenever we take the train from Norwich to London, the first stop is Diss. Often when I hear the conductor sternly announcing that station, I think of Eva Sansome cooped up in her kitchen preparing slides of Phytophthora oospores and carefully examining the spread out chromosomes with her microscope. That must have been quite a sight. My (older!) colleague Richard Michelmore experienced that first hand when he was doing his PhD on another oomycete pathogen the lettuce downy mildew Bremia lactucae. Richard visited Eva’s kitchen to learn directly from her how to prepare microscopy slides of Bremia chromosomes. Here you can see him relate that story at an oomycete conference in 2019 where he also told us that he inherited Eva’s original microscope slides demonstrating that oomycetes are diploid. I sure hope these slides will end up in a science museum one of these days to commemorate Eva Sansome’s landmark discovery.
Eva also collaborated with Clive Brasier, who at the time was early in his career, and they became really good friends. He’s moved on to become one of our most famous plant pathologists working at Forest Research and making major contributions to several areas of plant pathology, notably demonstrating the importance of inter-specific hybridization in Phytophthora. Clive wrote the chapter in the book about Eva.
Eva didn’t stop with demonstrating that oomycetes are diploid. She and Clive also showed that some Phytophthora can be polyploid, which means they can have more than two copies of every gene in their cells. That’s a really fantastic pioneering contribution that we all built on. Later on, research using new methods like genomics, where we can now sequence the genome of every organism including Phytophthora, confirmed this view that Phytophthora infestans is generally a diploid but that some strains can also be triploid or tetraploid (multiple gene copies). Here is work done by my colleagues Kentaro Yoshida and Hernàn Burbano who demonstrated just that in 2013 using genome sequencing — a methodology that Eva could only dream of at the time of her discovery.
But one sad thing about Eva Sansome is how she was never recognized by institutions like the Royal Society. She was a bit on the outside of academic research, having worked in Africa and then publishing out of her kitchen lab. So she never really got the recognition she deserved. The book talks about that; the chapter from Clive discusses this at the end. She was recognized in some ways, but perhaps not as much as she could have.
But then again Eva’s work stood the test of time, and her legacy lives in the research we do today. And this is the greatest honor any scientist can have.
Thank you. If you enjoyed reading these three stories, please do get a copy of this book and read about the other 24 pioneering women in plant pathology.
I’m very grateful to Jennifer Mach and Monica Harrington at PlantEditors for turning the transcript of the talk into the readable version posted above.