In the 1980s it was possible to express transgenes in cells of different organisms, but visualizing & assaying gene expression was still problematic. The lacZ β-galactosidase was a commonly used reporter, but compromised due to endogenous enzymes breaking down its substrates too.
So Jefferson developed the Escherichia coli uidA-encoded β-glucuronidase (GUS) reporter during his PhD in David Hirsh’s lab @CUBoulder. Adding a GUS-substrate to Caenorhabditis elegans carrying the GUS-reporter led to a colorful precipitate in all tissues with GUS expression.
Jefferson completed his PhD at a revolutionary time for the Plant Sciences. E.g., plant transformation & the CaMV35S promoter had just been established (see classics #6 & 9). So Jefferson decided to apply his GUS system to the creation of better performing transgenic crop plants.
He therefore joined the lab of plant transformation pioneer @michaelbevan565 at the Cambridge Plant Breeding Institute, now part of @JohnInnesCentre. Together they established GUS as a reporter in plants, initially using the CaMV 35S & ribulose bisphosphate carboxylase promoters.
They then used the GUS-reporter to analyze the activity of the patatin-1 promoter in transgenic potatoes in the world’s first field trial with a transgenic crop plant (beating Monsanto to this ‘First’ by 1 day!), finding that the field showed a higher variability than the lab.
However, during his time in England Jefferson also observed a big change in how science was being performed. The huge plant science innovations in the early 80s, most notably plant transformation, resulted in a patenting frenzy, which led to a more secretive atmosphere.
Not happy about this development, Jefferson decided to counteract this trend by making his GUS system available to everybody – a move which also resulted in the rapid uptake of the system in labs across the world.
Producing 10.000 GUS kits, containing the necessary plasmids & a detailed ‘GUS manual’, ready to use for anybody, they gave the system away for free (and license-free) to thousands of scientists via the mass-mailed Plant Molecular Biology Reporter newsletter.
This move made GUS one of the most widely used reporter systems in the world, and it also started Jefferson’s personal journey in the #OpenScience movement, which eventually (1992) led him to founding Cambia @CSIRO as an enterprise dedicated to making innovation freely available.
Cambia initially was a lab-based organization, developing & making tools available such as GUSPlus & the pCAMBIA vectors, or developing new bacteria able to transform plants, to circumvent the patent situation around agrobacterium-mediated plant transformation @nature in 2005.
Since the early 2000s Cambia primarily provides an infrastructure to share biotech tools and navigate the licensing and patenting landscape around biotech innovations, via their Biological Innovation for Open Society (#BiOS) initiative.
For more, have a look at this article by Richard Poynder, based on an interview with Jefferson: poynder.blogspot.com/2006/09/interv…
And the article by Jefferson, ‘Science as Social Enterprise: The CAMBIA BiOS Initiative’ here: doi.org/10.1162/itgg.2…
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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.
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.
#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…
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).
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:
#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…
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.
#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!
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.
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.
#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
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.
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... 🧵👇
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.
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.