UFMylation involves the covalent modification of substrate proteins with UFM1 (Ubiquitin-fold modifier 1) and is important for maintaining ER homeostasis. Stalled translation triggers the UFMylation of ER-bound ribosomes and activates C53-mediated autophagy to clear toxic polypeptides. C53 contains noncanonical shuffled ATG8-interacting motifs (sAIMs) that are essential for ATG8 interaction and autophagy initiation. However, the mechanistic basis of sAIM-mediated ATG8 interaction remains unknown. Here, we show that C53 and sAIMs are conserved across eukaryotes but secondarily lost in fungi and various algal lineages. Biochemical assays showed that the unicellular alga Chlamydomonas reinhardtii has a functional UFMylation pathway, refuting the assumption that UFMylation is linked to multicellularity. Comparative structural analyses revealed that both UFM1 and ATG8 bind sAIMs in C53, but in a distinct way. Conversion of sAIMs into canonical AIMs impaired binding of C53 to UFM1, while strengthening ATG8 binding. Increased ATG8 binding led to the autoactivation of the C53 pathway and sensitization of Arabidopsis thaliana to ER stress. Altogether, our findings reveal an ancestral role of sAIMs in UFMylation-dependent fine-tuning of C53-mediated autophagy activation.
Publikation
Ai, H.; Bellstaedt, J.; Bartusch, K. S.; Eschen‐Lippold, L.; Babben, S.; Balcke, G. U.; Tissier, A.; Hause, B.; Andersen, T. G.; Delker, C.; Quint, M.;Auxin‐dependent regulation of cell division rates governs root thermomorphogenesisEMBO J.42e111926(2023)DOI: 10.15252/embj.2022111926
Roots are highly plastic organs enabling plants to adapt to a changing below-ground environment. In addition to abiotic factors like nutrients or mechanical resistance, plant roots also respond to temperature variation. Below the heat stress threshold, Arabidopsis thaliana seedlings react to elevated temperature by promoting primary root growth, possibly to reach deeper soil regions with potentially better water saturation. While above-ground thermomorphogenesis is enabled by thermo-sensitive cell elongation, it was unknown how temperature modulates root growth. We here show that roots are able to sense and respond to elevated temperature independently of shoot-derived signals. This response is mediated by a yet unknown root thermosensor that employs auxin as a messenger to relay temperature signals to the cell cycle. Growth promotion is achieved primarily by increasing cell division rates in the root apical meristem, depending on de novo local auxin biosynthesis and temperature-sensitive organization of the polar auxin transport system. Hence, the primary cellular target of elevated ambient temperature differs fundamentally between root and shoot tissues, while the messenger auxin remains the same.
Publikation
Bagchi, R.; Melnyk, C. W.; Christ, G.; Winkler, M.; Kirchsteiner, K.; Salehin, M.; Mergner, J.; Niemeyer, M.; Schwechheimer, C.; Calderón Villalobos, L. I. A.; Estelle, M.;The Arabidopsis ALF4 protein is a regulator of SCF E3 ligasesEMBO J.37255-268(2018)DOI: 10.15252/embj.201797159
The cullin‐RING E3 ligases (CRLs) regulate diverse cellular processes in all eukaryotes. CRL activity is controlled by several proteins or protein complexes, including NEDD8, CAND1, and the CSN. Recently, a mammalian protein called Glomulin (GLMN) was shown to inhibit CRLs by binding to the RING BOX (RBX1) subunit and preventing binding to the ubiquitin‐conjugating enzyme. Here, we show that Arabidopsis ABERRANT LATERAL ROOT FORMATION4 (ALF4) is an ortholog of GLMN. The alf4 mutant exhibits a phenotype that suggests defects in plant hormone response. We show that ALF4 binds to RBX1 and inhibits the activity of SCFTIR1, an E3 ligase responsible for degradation of the Aux/IAA transcriptional repressors. In vivo, the alf4 mutation destabilizes the CUL1 subunit of the SCF. Reduced CUL1 levels are associated with increased levels of the Aux/IAA proteins as well as the DELLA repressors, substrate of SCFSLY1. We propose that the alf4 phenotype is partly due to increased levels of the Aux/IAA and DELLA proteins.
Publikation
Anh, N. T. H.; Thuy, T. T.; Sung, T. V.; Dan, T. K.; Chinh, N. B.; Quang, N.; Franke, K.; Arnold, N.; Wessjohann, L.;Phytochemical study on the plants of the antidrug medication heantos 4: Part 3. Homoisoflavonoid, flavonoid and phenolic compoundsVietnam J. Chem.51358-362(2013)
Anh, N. T. H.; Thuy, T. T.; Sung, T. V.; Dan, T. K.; Chinh, N. B.; Quang, N.; Franke, K.; Arnold, N.; Wessjohann, L.;Phytochemical study on the plants of the antidrug medication heantos 4: Part 2. Terpenoid- and steroid compoundsVietnam J. Chem.51190-194(2013)
Thuy, T. T.; Anh, N. T. H.; Sung, T. V.; Dan, T. K.; Chinh, N. B.; Quang, N.; Franke, K.; Arnold, N.; Wessjohann, L.;Phytochemical study on the plants of the antidrug medication heantos 4: Part 4. Phthalides, fatty acids, oligosaccharide esters and miscellaneous compoundsVietnam J. Chem.51546-550(2013)
Thuy, T. T.; Anh, N. H.; Sung, T. V.; Dan, T. K.; Chinh, N. B.; Quang, N.; Franke, K.; Arnold, N.; Wessjohann, L.;Phytochemical study on the plants of the antidrug medication heantos 4: Part 1. Alkaloids and other nitrogen containing compoundsVietnam J. Chem.51185-189(2013)
Khamko, V. A.; Dien, P. H.; Schmidt, J.; Quang, D. N.;Cytotoxic and antimicrobial constituents from the roots of Stemona cochinchinesis in LaosVietnam J. Chem.50203-206(2012)
Thuy, T. T.; Sung, T. V.; Franke, K.; Arnold, N.; Wessjohann, L.;Flavonone-C-glycosides from the seeds of Zizyphus Jujuba Mill var. Spinosa HuVietnam J. Chem.1-8(2007)
Ninh, P. T.; Anh, N. T. H.; Sung, T. V.; Wessjohann, L.;Studies on chemical constituents of the roots of Polygala sp.: II - Further phenylpropanoide sucrose estersVietnam J. Chem.45518-522(2007)