These vignettes are inspired by Mendel’s 200th anniversary and my August 2022 visit to Brno, Czech Republic. The first geneticist was a plant biologist.
Cite as: Kamoun, S. (2022). Happy birthday Gregor Mendel.Zenodo https://doi.org/10.5281/zenodo.7034491
The world of genetics celebrates the 200th anniversary of the Augustinian monk who first defined the laws of genetics while experimenting with various inherited traits of peas. Many don’t realise that the first geneticist was a plant biologist. Learn more about Mendel and his legacy by visiting the fabulous Gregor Mendel 200 website.
On the way to Brno
My Parisian taxi driver to the Charles de Gaulle airport was an ebullient African. He asked me about my destination. “Brno,” I answered, “have you heard of it?” The exchange went more or less like this:
“No, where is it?” asks the driver.
“It’s in the Czech Republic. Do you know what it’s famous for?” I replied.
“Nope. No idea.”
“That’s where Gregor Mendel invented genetics. Have you heard of Mendel?”
“Nope.”
“Have you heard of genetics?”
“Yeah, sure. That’s an important science in medicine.”
”Yes, you’re right. And Mendel basically was the first to have defined the rules of this science. Can you guess what he was working on?”
“I don’t know. Mouse?”
“Ha ha. No, he worked on les petit pois! (peas!)”
“No way. Get out of here!”
I guess it’s hard to imagine that the entire field of genetics, with the massive impact it’s having on all aspects of biomedicine, from cancer to pandemics, traces its origins to garden experiments with the humble petit pois. My driver seemed stunned. I hope he’ll spread the story to his family and friends.
A failure to replicate
Mendel’s paradigm-shifting discovery of the basic principles of genetic inheritance went against the leading theory of the 19th century —pangenesis — which wrongly assumed that inheritance occurs by blending of the parental characters. Nonetheless, Mendel’s work was overlooked until it was “rediscovered” early in the 20th century. Why was that?
Much has been written on the topic. From popular accounts like here and here, to academic textbooks, the reasons listed are many. Mendel’s 1865 lecture on the topic to the Brünn Natural History Society underwhelmed the audience, and he ended up publishing his 48-page articles article “Experiments on Plant Hybridization” in the Society’s journal, the little known Proceedings of the Natural History Society of Brünn. But the obscure journal may not have mattered much as the paper was relatively widely disseminated with Mendel sending dozens of copies to scientists and libraries. Even Charles Darwin may have received a copy.
Perhaps Mendel’s laws have remained unknown for so long due to poor science communication. Our job as scientists is to produce knowledge and to communicate it. When we discover new things, it’s important to not just communicate the facts of the research findings, but also their wider implications. This is why we should use the Discussion section of a research paper to speculate on the implications of our findings. I’m not a Mendel historian, so I’m most certainly way out of my depth here, but perhaps a shorter article that framed his pea genetics experiments in a broader context and explained how the results contradict pangenesis may have triggered wider attention beyond the 48-page technical paper. The article could have been provocatively titled “Why pangenesis is wrong.”
But then again, Gregor Mendel is described as humble and he may not have been inclined to the type of bombastic self-promotion we are used to today. In any case, a humble monk working on humble peas may have struggled to gain attention no matter what. But I still do wonder whether things would have been different if, say, he did his crosses with mice or rabbits. Could this be another case of plant blindness?
The Swiss botanist Carl Nägeli is often portrayed as the villain who discouraged Mendel from further work on plant hybridization. Nägeli worked on the highly polymorphic Asteraceae genus Hieracium (hawkweed) and urged Mendel to use this plant to replicate the laws of inheritance he discovered with peas (Pisum). As Gian Nogler wrote in a wonderful perspective article in the journal Genetics:
“Mendel hoped that the highly polymorphic genus Hieracium would be particularly promising for verifying the laws of inheritance that he had discovered while working on Pisum. But all his incredibly painstaking emasculation and crossing experiments on Hieracium led to results that, to his consternation, seemingly stood in direct contradiction to his laws:
- The F1 hybrids from crossings between, as he thought, “true breeding” strains were not uniform, as in Pisum; rather they varied in every conceivable way.
- The putative F2 generations, on the contrary, were uniform and did not segregate for any characters, as he would have expected.
These puzzling results caused Mendel (1869 and in his letters to Nägeli in 1866–1873; see CORRENS 1905) to consider how much Pisum and Hieracium might represent divergent laws of inheritance. Such a hypothetical existence of two different types of inheritance — a “Pisum type” and a “Hieracium type” — was a view shared even by de Vries, Correns, and Bateson in the first years after the rediscovery of Mendel’s laws.”
This failure to replicate his laws of inheritance must have cast doubt in Mendel’s mind as to whether his findings were of a fundamental nature. Only years later, it became clear that most Hieracium species reproduce by apomixis or asexual reproduction by seeds, which explains the seemingly contradictory results that Mendel observed.
It’s, therefore, tempting to conclude that a lack of orthogonal replication of the Pisum hybridization experiments have deflated Mendel and demotivated him from generalizing his laws into fundamental principles of genetics. But as science moved on, we now know that his work has laid the foundation to our modern understanding of genetics.
Sister love
Mendel had a hard time during his studies at Francis University in Olomouc. He was broke and felt lonely because he didn’t speak the Czech language. He became depressed and took a break from his studies to spend time with his family in his native village of Heinzendorf (now called Hynčice) in the Silesian countryside. That’s when his sister, Theresa, decided to give him a piece of her inheritance to support his studies. Theresa was only 13 at the time. I don’t know when she was born, but I would like to celebrate her birthday too.
Model system — give peas a chance
In Brno, we were offered a copy of the wonderful comics book of Lucie Seiferová: Gregor Johann Mendel and the Trouble-Ridden story of genes. The book starts with a 1902 quote from British geneticist William Bateson who championed and popularized Mendel’s work once it was rediscovered by Hugo de Vries and Carl Correns in 1900.
“Reading Mendel’s work I felt a greater joy than I can describe. It made me feel like a traveller on a long journey who suddenly finds that thanks to someone else, the goal is much closer than he had imagined.”
William Bateson hits close to home given that in 1910 he became the Founding Director of the John Innes Horticultural Institution, now the John Innes Centre on the Norwich Research Park campus where my home institute The Sainsbury Laboratory is also located. The John Innes building adjacent to my lab is named after Bateson. But if you ever wander in the Bateson, be extra careful. This is where Saskia Hogenhout’s phytoplasma lab is located and I hear the building is infested with Zombie plants. [Just kiddin’ okay]
Bateson is famous for having first used the term ‘genetics’. He started off as an embryologist in Cambridge, but, inspired by Mendel’s genetics, he morphed into a plant biologist. Prior to the John Innes, Bateson led a School of Genetics in Cambridge, which stood out by the number of women scientists he recruited from Newnham College — the legendary Newnham College Mendelians.
At the fledgling John Innes Institution, Bateson and colleagues decided to give peas a chance and turn Mendel’s favorite plant into a model system for genetic studies. They kicked off what turned into a long tradition of pea genetics at the Institute. They made seminal contributions, notably discovering genetic linkage and articulating the concept of epistasis.
Their work, however, wasn’t without controversy. Due to the confounding effects of epigenetic paramutation, the number of linkage groups they discovered was superior to the number of chromosomes. This led Bateson to reject the chromosome theory — that genes are on specific locations on chromosomes — developed by Thomas H. Morgan in the US and others. As with Mendel’s hawkweed, the lack of orthogonal support for a theory created confusion. And as in the case of hawkweeds, peculiar aspects of plant biology confounded the interpretation of the findings.
From pea genetics to genomics
The work on pea genetics at the John Innes Centre continues. My colleague Sanu Arora, holder of the Ben Gill Translational Fellowship at the John Innes Centre, has expanded the genetic work to genomics. Sanu is building up an ambitious research program drawing on the incredible natural diversity of the genus Pisum that has caught Mendel and Bateson eyes.
Legumes like peas are critical to feeding the planet and to sustainable agriculture. They establish symbioses with nitrogen-fixing bacteria — thus growing in nutrient poor soil sand helping to fertilize them— and often have the genes to cope with environmental stresses like drought. With the tools of genomics and gene editing, plant biologists like Sanu and many others are building on Mendel’s legacy with an incredible level of sophistication. Gregor Mendel’s seminal garden experiments are reincarnated in these modern investigations.
Happy birthday dear Gregor!
Acknowledgements
I’m grateful to Marília Horta Jung, Thomas Jung and the team behind the 21st Annual Meeting of the Oomycete Molecular Genetics Network held at Mendel University in Brno for the opportunity to visit the city on this momentous year. Click here for the #OMGN22 tweets.
This post is dedicated to Amena Khatun Rupa, University of Adelaide, who had to leave Brno under difficult circumstances. It was a pleasure to meet Amena in Brno and I enjoyed her excellent presentation on how a plant defensin affects a pathogenic microbe.
