Florent Waltz

Happy to share our new preprint on the mechanism of human tRNA 3' CCA maturation! This project was spearheaded by Bernhard Kuhle in my group, with contributions from many others and a great collaboration with the group of Peter Rehling (UMG). See highlights below!

www.biorxiv.org/content/10.6...

There is a week left to apply for two available positions in my lab @ipbhalle.bsky.social

- PhD: ipb-halle.mhm.jobs/12-phd-posit...

- Postdoc: ipb-halle.mhm.jobs/13-postdocto...
Earliest start date: 01/05/2026.

We are interested in plant immune receptor biochemistry and evolution. Please share!

Had a great time in Zurich for the annual LS² meeting. Nice gathering of the swiss scientific community, always cool to see what the neighbors are doing 😜

Thank you Ahmad! That's a good question, we are not entirely sure! The position could be compatible for potential trans-acting factors (present in chlamy) binding there for specific translation initiation events (5'UTR binding maybe), a bit similar to what was recently described for yeast mitoribos

Chloroplast-encoded small subunit extensions reshape the Chlamydomonas chlororibosome https://www.biorxiv.org/content/10.64898/2026.02.07.704542v1

Chloroplast-encoded small subunit extensions reshape the Chlamydomonas chlororibosome www.biorxiv.org/content/10.64898/2026.02.07.704542v1 #cryoEM

For this work, we used the publicly available Chlamy dataset (www.ebi.ac.uk/empiar/EMPIA...) which was recently published.
www.cell.com/molecular-ce...
Check it out!
Thanks to the co-authors @phaips.vd.st, Philippe Lehner, @pfeffercryolab.bsky.social , Lukas Kater and @cellarchlab.com !

It was a fun dive into the chloroplast! After working so much on mitoribosomes (which are weird and divergent!) I always assumed chlororibosomes were more conserved and bacterial-like. Turns out they might be more diverse than expected!
It was fun, but now, back to mitochondria!

We observed that these protein extensions localize around the mRNA exit and entry channels, extending them to create more stable mRNA threading. This likely enhances polysome stability and could play a role in chloroplast-specific translation regulation.

Combined with single-particle cryo-EM, we identified all the proteins in this “hat.” Turns out it’s more of an arm 🦾, rooting from the body it reaches for the head! It is composed of large extensions in conserved proteins S2, S3, S4, and S5, as well as three specific proteins.

Interestingly, these chlororibosomes are loosely bound to the thylakoid membranes. High heterogeneity made classification challenging to find clean thylakoid-bound ribosomes! The comparison with cytosolic and mitoribosomes shows how rigidly the latter bind membranes compared to the chlororibosomes.

Historical perspective 👴: this project predates me! In 2021, I joined @cellarchlab.com (at MPI) to work on mitoribosomes, but Ben tried to lure me with a mysterious "hatted" chlororibosome. @pfeffercryolab.bsky.social did an initial average 8 y.a. as a postdoc, but it stayed in a drawer until now!

Long in the making, but happy to present the Chlamydomonas chlororibosome!
Cryo-ET🔬reveals a large new domain on the small subunit, built from multiple extensions in conserved ribosomal proteins.
bioRxiv 📖: shorturl.at/q44tG
This suggests greater chlororibosome diversity than expected!
1/n 🧵

For #ECR’s:

DBG’s Hot Tpoic Workshop
on Cryo-Electron Tomography + FIB-milling

13 – 15 April 2026
In @cellarchlab.com 's lab @biozentrum.unibas.ch

Organised by @tamb-o.bsky.social, Karen Zinzius, @fannyleblanc.bsky.social

Details: www.deutsche-botanische-gesellschaft.de/en/about-us/...

Am I the only one increasingly annoyed by cryo-EM papers not showing *any* experimental density in figures? Sometimes not even in the supplementary material??

Check this new study on carbon concentration mechanisms!

See how the pyrenoid changes by modifying Rubisco linkers in our favorite alga, Chlamy 💚!

My desk mate @phaips.vd.st spent a lot of time collecting & carefully analyzing these beautiful tomograms 🔬.

Congrats to all the authors!

You like #LLPS? #TeamTomo? #Rubisco? Check out our latest preprint!

What a great collaboration this has been!

This one was quite the journey! The paper describing the #ChlamyDataset is finally out and on the cover of Mol Cell!

This beautiful rendering made by co-author @jessheebner.bsky.social and Holly Peterson shows an instance of mitochondrial fission found in the dataset 😍

[Maybe long thread ahead]

The latest issue is now online www.cell.com/molecular-ce...

Toward community-driven visual proteomics with large-scale cryo-electron tomography of Chlamydomonas reinhardtii Using the latest advances in instrumentation and computational workflows, Kelley et al. present a large-scale annotated cryo-electron tomography dataset of the model green alga, Chlamydomonas reinhardtii. This unprecedented community resource is rich in high-resolution biological information and empowers the development of new methods for visual proteomics.

Online Now: Toward community-driven visual proteomics with large-scale cryo-electron tomography of Chlamydomonas reinhardtii Online now:

Nighttime cityscape of Tokyo with dense illuminated skyscrapers and Tokyo Tower glowing orange on the right. Centered over the skyline is the EU–Japan logo combining the European Union and Japanese flags, with the text “EU–JAPAN” and “HORIZON EUROPE” beneath it. The European Commission logo appears in the bottom-right corner.

Japan is joining Horizon Europe, the EU’s flagship research and innovation programme.

Openness and international cooperation can shape a bright future for science and technology.

Through science, we can build bridges, strengthen competitiveness, and accelerate the green and digital transitions.

The value of publishing negative data - News Scientific journals love news-worthy results. Editors want to publish studies with novel data that scientists will eagerly read and cite in their own work. Because of this desire for novelty, studies ...

Giving the gift of negative data 🥰

Since I joined @lsajournal.org I have handled several stellar manuscripts that report null results. These papers do very well and reviewers almost always appreciate them!

Thanks @rockefeller.edu news team for the article!

www.rockefeller.edu/news/38829-t...

Happy to see this out 🥳

authors.elsevier.com/sd/article/S...

#TeamTomo #CryoET #CryoEM

And one more story 🎩 and surprise 📔 to come in January, so stay tuned.

If you want to learn how to process cryo-ET data using the Chlamy dataset don't forget to check : tomoguide.github.io
@phaips.vd.st

Final version is out! Our large-scale cryo-ET dataset 🔬 of Chlamydomonas reinhardtii 🦠 is now published in @cp-molcell.bsky.social

Huge collaborative effort! So glad to see the community already using it to develop new resources & tools.

Check it out here: shorturl.at/z4i4c
#CryoEM #CryoET

Now waiting for the software that will revitrify my lamellae 🔥🧊

Structural insights into cauliflower mitoribosome in translation state and in association with a late assembly factor pubmed.ncbi.nlm.nih.gov/41330901/ #cryoEM

Congrats Marco 🎉! I still remember you talking about that back in Strasbourg, great to see the full story now!

AGO5 restricts virus vertical transmission in plant gametophytes The propagation of a viral infection from a host parent to its progeny is known as vertical transmission, or seed transmission in plants. It allows viral infections to rapidly spread locally via polle...

Preprint alert! It is my great pleasure to announce the first manuscript from the lab, a story that started @gmivienna.bsky.social and was mainly accomplished by the intrepid @gesahoffmann.bsky.social at @mpi-mp-potsdam.bsky.social. A brief thread with our findings
www.biorxiv.org/content/10.1...