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Happy to share our new preprint describing a set of GDSL-domain containing proteins that regulate suberin homeostasis in the endodermis. This describes a long journey with @Robertas_U and @NikoGeldner et al! https://www.biorxiv.org/content/10.1101/2020.06.25.171389v1
The idea of the experiment started 10 years ago when I was a little post-doc with @NikoGeldner. We got a bit distracted by the communication between the pericycle and endodermis -> https://science.sciencemag.org/content/343/6167/178.long
This also fuels the start of my own group. However, I was not allowed to leave Niko's lab before I performed the transcriptomics experiment described in the current preprint. Luckily, at the end of my post-doc @Robertas_U joined the Geldnerlab.
@Robertas_U did an amazing job in tackling this data-set without any fear of the beast of genetic redundancy. Together we noticed a large number of GDSL-domain containing proteins that were differentially regulated....
Five were repressed by auxin and five were induced by auxin. All of them were expressed in the endodermis. We hypothesised that these auxin repressed GELPs could be important for suberin deposition in the endodermis...
Of course, single mutants showed no phenotype. Thus, @Robertas_U decided to just crispr all five of them in one go. After a significant amount of genotyping, @Robertas_U isolated 2 allelic series of quintuple gelp knock-outs...
..in which we could not detect any suberin in the endodermis using flurol yellow staining! Chemical analysis also revealed a ~85% reduction in suberin! Interestingly, the lateral root cap cuticle was not affected.
Under controlled conditions these mutants were quite normal. However, as soon as they were exposed to mild salt stress, they were severely affected. Interesting, the expression of known suberin biosynthesis genes was not affected in the mutant..
..and that we have identified the core set of GELPs that regulate suberin polymerisation in the apoplast. The latter was confirmed via a fluorescent protein-tagged GELP38 that fully restored suberin lamellae formation.
But what about they other five GELPs that were induced by auxin? All of these were also either expressed in the endodermis or induced in this layer during lateral root formation....
As suberin is removed during this process, we hypothesised that this group could be suberin degrading enzymes. Indeed, upon inducible over-expression in the endodermis, 3 out of 5 of these GELPs could degrade suberin. When looking at the knock-out mutants of these GELPs..
We observed that several of them had a strong delay in lateral root emergence! Strikingly, we observed the strongest phenotypes in the two GELPs for which we could not show suberin degradation activity...I guess there are still a few things left for us to figure out...
Anyway, I hope you enjoy reading this work and we look forward to receive feedback! Finally, this work was made possible via generous funding from @snsf_ch. And to @NikoGeldner for giving @Robertas_U and me all the freedom to bring this project to a good end!
