ORCID Profile
0000-0002-4440-1776
Current Organisation
University of Oxford
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Publisher: Cold Spring Harbor Laboratory
Date: 13-08-2023
DOI: 10.1101/2023.08.11.552970
Abstract: Chloroplast biogenesis is dependent on master regulators from the Golden2-like (GLK) family of transcription factors, but higher order glk mutants contain residual chlorophyll and therefore other proteins must also be involved. Here we identify MYB-related transcription factors as regulators of chloroplast biogenesis in the liverwort Marchantia polymorpha and angiosperm Arabidopsis thaliana . In both species, double mutant alleles in MYB-Related genes show very limited chloroplast development and photosynthesis gene expression is perturbed to a greater extent than mutants of GLK . In M. polymorpha MYB-related genes act upstream of GLK , while in A. thaliana this relationship has been rewired. In both species, genes encoding enzymes of chlorophyll biosynthesis are controlled by both MYB-related and GLK proteins whilst those allowing CO 2 fixation, photorespiration as well as photosystem assembly and repair require the MYB-related proteins. Thus, MYB-related and GLK genes have overlapping as well as distinct targets. We conclude that MYB-related transcription factors act with GLK to orchestrate chloroplast development in land plants.
Publisher: Wiley
Date: 26-10-2023
DOI: 10.1111/NPH.19343
Publisher: Wiley
Date: 10-2022
DOI: 10.1002/PLD3.455
Abstract: A key feature of C 4 Kranz anatomy is the presence of an enlarged, photosynthetically highly active bundle sheath whose cells contain large numbers of chloroplasts. With the aim to identify novel candidate regulators of C 4 bundle sheath development, we performed an activation tagging screen with Arabidopsis thaliana . The reporter gene used encoded a chloroplast‐targeted GFP protein preferentially expressed in the bundle sheath, and the promoter of the C 4 phospho enol pyruvate carboxylase gene from Flaveria trinervia served as activation tag because of its activity in all chlorenchymatous tissues of A. thaliana . Primary mutants were selected based on their GFP signal intensity, and one stable mutant named kb‐1 with a significant increase in GFP fluorescence intensity was obtained. Despite the increased GFP signal, kb‐1 showed no alterations to bundle sheath anatomy. The causal locus, AT1G29480, is specific to the Brassicaceae with its second exon being conserved. Overexpression and reconstitution studies confirmed that AT1G29480, and specifically its second exon, were sufficient for the enhanced GFP phenotype, which was not dependent on translation of the locus or its parts into protein. We conclude, therefore, that the AT1G29480 locus enhances the GFP reporter gene activity via an RNA‐based mechanism.
Publisher: Cold Spring Harbor Laboratory
Date: 12-12-2022
DOI: 10.1101/2022.12.07.519530
Abstract: In leaves of C 4 plants the reactions of photosynthesis become restricted between two compartments. Typically, this allows accumulation of C 4 acids in mesophyll cells and subsequent decarboxylation in the bundle sheath. In C 4 grasses proliferation of plasmodesmata between these cell types is thought to increase cell-to-cell connectivity to allow efficient metabolite movement. However, it is not known if C 4 dicotyledons also show this enhanced plasmodesmal connectivity and so whether this is a general requirement for C 4 photosynthesis is not clear. How mesophyll and bundle sheath cells in C 4 leaves become highly connected is also not known. We investigated these questions using 3D- and 2D- electron microscopy on the C 4 dicotyledon Gynandropsis gynandra as well as phylogenetically close C 3 relatives. The mesophyll-bundle sheath interface of C 4 G. gynandra showed higher plasmodesmal frequency compared with closely related C 3 species. Formation of these plasmodesmata was induced by light. Pharmacological agents that perturbed chloroplast development or photosynthesis reduced the number of plasmodesmata, but this inhibitory effect could be reversed by the provision of exogenous sucrose. We conclude that enhanced formation of plasmodesmata between mesophyll and bundle sheath cells is wired to the induction of photosynthesis in C 4 G. gynandra .
Publisher: Cold Spring Harbor Laboratory
Date: 23-01-2023
DOI: 10.1101/2023.01.23.525199
Abstract: Photosynthesis in eukaryotic cells takes place in specialised plastids. The regulation of plastid development is crucial for multicellular systems such as plants. Two families of transcription factors known as Golden2-like (GLK) and GATA regulate plant chloroplast development, and the miR171-targeted SCARECROW-LIKE (SCL) GRAS transcription factors regulate chlorophyll biosynthesis. The extent to which these proteins carry out conserved roles in non-seed plants such as the liverworts is not known. Here we determine the degree of functional conservation of the GLK, GATA and SCL proteins in controlling chloroplast development in the model liverwort Marchantia polymorpha . Our results indicate that GATA and SCL do not play a detectable role in chloroplast biogenesis but loss of GLK function leads to reduced chloroplast size, underdeveloped thylakoid membranes and lower chlorophyll accumulation. These findings suggest that the functioning of GATA and SCL in chloroplast development either evolved after the ergence of vascular plants from bryophytes, that both roles were secondarily lost in M. polymorpha , or that functional redundancy is masking their roles. In contrast, and consistent with its presence in algae, GLK plays a conserved role in chloroplast biogenesis of liverworts and vascular plants.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Tina B. Schreier.