Marc Somssich Profile picture
Mar 31, 2022 12 tweets 4 min read Read on X
#PlantScienceClassics #15 #PlantScienceFails #1: The auxin-independent (axi) Nicotiana tabacum lines. In 1992 Richard Walden et al. (specifically co-worker Inge Czaja) published activation-tagged axi protoplasts @ScienceMagazine that could divide&grow in the absence of any auxin! Title page of the retracted...
The development of plant transformation in the early 1980s (classics #6&13) was inspirational for many scientists. Among them was Richard Walden, who teamed up with plant transformation pioneers Barbara & Thomas Hohn to leverage this advance to develop the “Agroinfection" method. Title page of the 1986 PNAS...
He then joined the next transformation pioneer, Jeff Schell, to develop more such tools. Their first was Activation-Tagging: 4 CaMV 35S enhancers (classic#9) were placed at the RB of the T-DNA. That way, they would overexpress the plant gene next to which the T-DNA was inserted. Figure 1 of the paper showi...
Walden used this technique to screen transformed N. tabacum protoplasts for their ability to divide & grow into calli & healthy plants – without the addition of any auxin to the culture medium, otherwise assumed to be an absolute necessity.
Surprisingly, he & his team were indeed able to isolate protoplasts that grew in the absence of any auxin. And even protoplasts from T2 & T3 plant descendants of these original regenerated plants retained this ability. The lines were thus called auxin-independent growth (axi). Figure 2 from the paper sho...
Not surprisingly, this huge result spawned several more high-impact papers & collaborations with other researchers eager to use the technique & Walden's auxin-independent protoplasts. Importantly though, the actual protoplast work had to be done by Walden's technician Inge Czaja. A list of papers using the ...
Curiously, only Czaja was able to work with the protoplasts, while postdocs & PhD students in the lab were unable to perform the work. Over the next years Czaja gave several reasons for this, starting with her experience in handling the protoplasts, to her playing Mozart to them.
However, when postdocs, students or collaborators didn't mention to Czaja the expected outcome of their experiments, her results still always seemed to fit their hypothesis, putting slowly emerging concerns to rest - at least for some time.
When other group leaders in the department eventually stepped up to Walden and demanded blind tests to be done, Walden refused. Eventually postdocs did these tests without Walden's permission, and indeed found that Czaja would tailor her results to fit their expectations.
When she was previously given experiments without being told the expectation, she later confessed that she would always sit with the researchers at lunch to eventually find out the expected outcome indirectly. She then added auxin to the correct cultures, initiating growth.
Walden denied any knowledge or wrongdoing, but he and Czaja resigned from their positions in 1997. He immediately took up a position at Horticulture Research International in East Malling, Kent, U.K, with funding from the BBSRC & the East Malling Trust for Horticultural Research.
It was left to Jeff Schell and Walden's former co-workers to clean up the mess. In months of work they repeated all key experiments, published them in a paper in @ThePlantJournal and then initiated retractions of all affected papers. Walden did not agree with the retractions. Title page of the 1997 The ...

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More from @somssichm

Mar 26, 2023
#PlantScienceClassics #18: Ethylene triple response mutants. 35 years ago Anthony Bleecker et al. exploited the triple response phenotype to identify the #ethylene receptor ETR1. The ethylene story is another example for #PlantBlindness @NobelPrize. doi.org/10.1126/scienc… The Science cover picture of the 1988 issue shows the triple
Ethylene is a gaseous #phytohormone with a wide range of roles from plant development to immunity. Ernest Starling in 1905 defined a hormone as mobile chemical messenger synthesized by a multicellular organism, that has physiological activity distant from the site of synthesis. Excerpt from Ernest Henry Starling’s 1905 paper “The Cro
The effect of ethylene on plants was first noted in the 1900s, when it leaked from illumination gas used in lamps and affected plants nearby. But it was Dimitry Neljubow, who in a series of experiments identified ethlyene as the active substance in the illumination gas in 1905.
Read 17 tweets
Oct 12, 2022
#PlantScienceClassics #17: The Mildew Resistance Locus O (MLO). 80 years ago Rudolf Freisleben & Alfred Lein created the first powdery mildew resistant barley plant. 30yrs ago the gene was mapped, 25yrs ago cloned-yet it's mode of action remains a mystery. doi.org/10.1007/BF0148… A portrait of Rudolf Freisl...
Powdery mildew is a fungal disease of many crop plants, most prominently maybe barley and wheat, where outbreaks can reduce grain quality & yield, and ruin complete harvests. Visible are the fluffy patches formed by the fungus (Blumeria graminis f. sp. hordei). A leaf and awn from a barle...
Freisleben used radiation-induced mutagenesis to create the barley 𝘮𝘭𝘰 mutant, which showed full resistant to this pathogen. A massive agricultural breakthrough!
See also Classic #2, to read about how Emmy Stein has developed this technique in 1921:
Read 12 tweets
Apr 8, 2022
#PlantScienceClassics #16: A linkage map of Arabidopsis thaliana. In 1983 the legendary Maarten Koornneef published a genetic map of A. thaliana, the basis for genetic work & an important contribution towards the acceptance of Arabidopsis as plant model. doi.org/10.1093/oxford… Title page of the 1983 pape...
In the early 1980s scientists finally adopted A. thaliana as model plant. At this point, several mutants were available, but their positions in the genome were mostly unknown. This was years before genome sequences became available,&genetic maps were still based on recombination.
Arabidopsis pioneer György Rédei did linkage analyses with 14 loci in the 1960s, but his genetic map from 1965 suggested 6 linkage groups – 1 more than chromosomes. Curiously, A. D. McKelvie created another map in parallel - & found 4 groups, 1 less than chromosomes. György Rédei’s linkage map,...A. D. McKelvie’s linkage ma...
Read 14 tweets
Jan 25, 2022
#PlantScienceClassics #14: Mendelian inheritance. In 1866 Gregor Mendel published his work on dominant/recessive trait inheritance in peas, establishing the hereditary rules on which modern genetics is based. But nobody cared,& his scientific career ended. biodiversitylibrary.org/page/48299076 A portrait of Gregor Mendel...
Mendel had always been interested in nature, and grew/kept and observed plants and bees in his parent’s garden. He later decided to become a monk and teacher. However, he failed teacher’s exam in 1850 & 1856, & eventually settled on being a monk and substitute teacher.
He satisfied his curiosity as a naturalist by keeping and observing plants and bees in the monastery garden, and eventually became interested in how traits are determined through generations. So he started to conduct crossing experiments with mice with grey or white fur. An image of Mendel’s garden...
Read 19 tweets
Jan 20, 2022
Do you know Daisy Roulland-Dussoix? She is one of the discoverers of restriction enzymes, who’s findings paved the way for the development of recombinant DNA and cloning technologies. Accordingly, the finding was rewarded with a #NobelPrize. But the prize didn’t go to her... 🧵👇 A portrait of Daisy Roulland-Dussoix from Wikipedia.
Daisy Roulland-Dussoix worked with Werner Arber to study the mechanism for the observed host-specificity of λ Phages. It was known from an important 1953 paper (Bertani & Weigle) that phages, that had replicated in a certain E. coli strain, could only re-infect the same strain. Title page of the 1953 paper from G. Bertani and J. J. Weigl
Roulland-Dussoix & Arber showed that host-specificity is linked with the phage’s DNA. Using phages carrying radiolabeled DNA, they showed that progeny with 2 parental DNA strands retained specificity, while progeny with newly synthesized daughter strands could adapt to new hosts. Title page of the first paper by Werner Arber and Daisy DussExcerpt from the paper stating ‘(2) All progeny λ K(Pl) p
Read 11 tweets
Jan 18, 2022
#PlantScienceClassics #13: Floral Dip. Almost 25 years ago, in 1998, Steven Clough & Andrew Bent published their geniously simple Arabidopsis transformation protocol @ThePlantJournal: Dipping a plant upside down into Agrobacterium solution - et voilà! doi.org/10.1046/j.1365… The title page of the 1998 ...
I have covered the plant transformation backstory in Classic#6, the T-DNA, so here I will focus on the events after 1983, the year plant transformation was established. These first transformants all were plants regenerated from cultured cells as calli.
Simply transforming an adult plant was not yet possible. One of the prerequisite toward this aim was the acceptance of Arabidopsis thaliana as a model plant (see also Classic#4), and the demonstration that A. thaliana was transformable via Agrobacterium.
Read 13 tweets

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