Biology subjects

Schulten, A.

Publications and source records attributed to Schulten, A..

4 recordsLinked to original sources

bioRxiv2024

Functional specialization of Arabidopsis VEL polymerization domains in the switch to Polycomb silencing

Cold-induced epigenetic silencing of Arabidopsis FLOWERING LOCUS C (FLC) requires the Polycomb Repressive Complex 2 and accessory proteins VIN3 and VRN5. VIN3 and VRN5 interact via head-to-tail VEL polymerization domains, but how these functionally contribute to the switch to an epigenetically silenced state remains poorly understood. Here, we determine that VIN3 VEL polymerization involves higher order nuclear VIN3 assemblies in vivo, promotes strong chromatin association and efficient H3K27me3 nucleation. However, we also show that the polymerization domains of VIN3 and VRN5 are not equivalent: VRN5 VEL domain is not required for silencing despite its role in physically connecting VIN3 with the PRC2 complex and VRN5 VEL is unable to functionally replace VIN3 VEL in vivo. Both VIN3 and VRN5 homologs are present throughout angiosperm species, suggesting a functional requirement for maintaining different polymerization modalities. This work reveals distinct roles for multifunctional polymerization domains of Polycomb accessory proteins underpinning the onset of epigenetic silencing.

plant biology↗

bioRxiv2023

Distinct accessory roles of Arabidopsis VEL proteins in Polycomb silencing

Polycomb Repressive Complex 2 (PRC2) mediates epigenetic silencing of target genes in animals and plants. In Arabidopsis, PRC2 is required for the cold-induced epigenetic silencing of the FLC floral repressor locus to align flowering with spring. During this process, PRC2 relies on VEL accessory factors, including the constitutively expressed VRN5 and the cold-induced VIN3. The VEL proteins are physically associated with PRC2, but their individual functions remain unclear. Here, we show an intimate association between recombinant VRN5 and multiple components within a reconstituted PRC2, dependent on a compact conformation of VRN5 central domains. Key residues mediating this compact conformation are conserved amongst VRN5 orthologs across the plant kingdom. By contrast, VIN3 interacts with VAL1, a transcriptional repressor that binds directly to FLC. These associations differentially affect their role in H3K27me deposition: both proteins are required for H3K27me3, but only VRN5 is necessary for H3K27me2. Although originally defined as vernalization regulators, VIN3 and VRN5 co-associate with many targets in the Arabidopsis genome that are modified with H3K27me3. Our work, therefore, reveals the distinct accessory roles for VEL proteins in conferring cold-induced silencing on FLC, with broad relevance for PRC2 targets generally.

plant biology↗

bioRxiv2021

Energy status-promoted growth and development of Arabidopsis require copper deficiency response transcriptional regulator SPL7

Copper (Cu) is a cofactor of around 300 Arabidopsis proteins including photosynthetic and mitochondrial electron transfer chain enzymes critical for ATP production and carbon fixation. Plant acclimation to Cu deficiency requires the transcription factor SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE7 (SPL7). We report that in the wild type and in the spl7-1 mutant, respiratory electron flux via Cu-dependent cytochrome c oxidase remained unaffected under both normal and low-Cu cultivation conditions. Contrary to the wild type, supplementing Cu-deficient media with exogenous sugar failed to stimulate growth of spl7-1. The spl7-1 mutant accumulated carbohydrates including the signaling sugar trehalose 6-phosphate, as well as ATP and NADH, also under normal Cu supply and without sugar supplementation. Late flowering of spl7-1 was in agreement with its attenuated sugar responsiveness. Functional TOR and SnRK1 kinase signaling in spl7-1 suggested against fundamental defects in these energy-signaling hubs. Sequencing of chromatin immunoprecipitates combined with transcriptomics identified direct targets of SPL7-mediated positive regulation, including FE SUPEROXIDE DISMUTASE1 (FSD1), COPPER-DEFICIENCY-INDUCED TRANSCRIPTION FACTOR1 (CITF1) and uncharacterized bHLH23 (CITF2), as well as an enriched upstream GTACTRC motif. In summary, transducing energy availability into growth and reproductive development requires the function of SPL7. Our results could help to increase crop yields, especially on Cu-deficient soils.

plant biology↗

bioRxiv2019

Do Arabidopsis Squamosa promoter binding Protein-Like genes act together in plant acclimation to copper or zinc deficiency?

The genome of Arabidopsis thaliana encodes approximately 260 copper (Cu)-dependent proteins, which include enzymes in central pathways of photosynthesis, respiration and responses to environmental stress. Under Cu-deficient growth conditions, Squamosa promoter binding Protein-Like 7 (SPL7) activates the transcription of genes encoding Cu acquisition systems and mediates a metabolic reorganization to economize on Cu. The transcription factor SPL7 groups among comparably large proteins in the SPL family, which additionally comprises a second group of small SPL proteins targeted by miRNA156 with roles in plant development. SPL7 shares extended regions of sequence homology with SPL1 and SPL12. Therefore, we investigated the possibility of a functional overlap between these three members of the group of large SPL family proteins. We compared the spl1 spl12 double mutant and the spl1 spl7 spl12 triple mutant with the wild type and the spl7 single mutant under normal and Cu-deficient growth conditions. Biomass production, chlorophyll content and tissue elemental composition at the seedling stage, as well as plant and flower morphology during reproductive stages, confirmed the involvement of SPL7, but provided no indication for important roles of SPL1 or SPL12, in the acclimation of Arabidopsis to Cu deficiency. Furthermore, we analyzed the effects of zinc (Zn) deficiency on the same set of mutants. Different from what is known in the green alga Chlamydomonas reinhardtii, Arabidopsis did not activate Cu deficiency responses under Zn deficiency, and there was no Cu overaccumulation in either shoot or root tissues of Zn-deficient wild-type plants. Known Zn deficiency responses were unaltered in spl7, spl1 spl12 and spll spl7 spl12 mutants. We observed that CuZnSOD activity is strongly downregulated in Zn-deficient A. thaliana, in association with an about 94% reduction in the abundance of the CDS2 transcript, a known target of miR398. However, different from the known Cu deficiency responses of Arabidopsis, this Zn deficiency response was independent of SPL7and not associated with an upregulation of MIR398b primary transcript levels. Our data suggest that there is no conservation in A. thaliana of the crosstalk between Zn and Cu homeostasis mediated by the single SPL family protein CRR1 in Chlamydomonas. In the future, resolving how the specificity of SPL protein activation and recognition of target gene promoters is achieved will advance our understanding of the specific functions of different SPL family proteins in either Cu deficiency response regulation or growth and development of land plants.\n\n\n\nO_TBL View this table:\norg.highwire.dtl.DTLVardef@fadf53org.highwire.dtl.DTLVardef@5bcffborg.highwire.dtl.DTLVardef@1b38ee7org.highwire.dtl.DTLVardef@16aeff3org.highwire.dtl.DTLVardef@1af5e1f_HPS_FORMAT_FIGEXP M_TBL C_TBL

plant biology↗