1,721,084 research outputs found
STAY-GREEN overexpression in dark-incubated leaves promotes the formation of transitional chromoplast-like plastids
No full text[EN] The transition of chloroplasts into chromoplasts and gerontoplasts during fruit ripening and leaf senescence, respectively, involves chlorophyll breakdown and chloroplast deterioration. Chlorophyll removal is carried out by several enzymes. Among them, the Mg-dechelatase STAY-GREEN (SGR) catalyzes the first step of chlorophyll degradation. The tomato green-flesh (gf) and pepper chlorophyll retainer (cl) mutants are SGR loss-of-function mutants that maintain high levels of thylakoid structures during chromoplast development in ripening fruits. Here, by overexpressing SGR in nonilluminated Nicotiana benthamiana leaves, we demonstrated that SGR triggers the onset of chloroplast deterioration, resulting in the formation of orange-leaf sectors containing plastids with carotenoid-bearing structures, although carotenoid production is not induced. Metabolite, microscopy, and transcriptome analyses suggested the onset of chloroplast senescence, indicating a possible transitional plastid stage in SGR-overexpressing regions. Overall, our work demonstrates the remarkable ability of plant plastids to adapt their ultrastructure to accommodate the precise metabolic composition of various developmental and environmental contexts.; STAY-GREEN induces chloroplast deterioration in dark-incubated leaves, resulting in transitional plastids with chromoplast-like features, revealing plastids' structural adaptation to metabolic status.This work was funded by grants from the Seed Industry Revitalization Project of Jiangsu Province of China (no. JBGS[2021]033) and the National Natural Science Foundation of China (no. 32470271) to S.L. and from Spanish MCIN/AEI/10.13039/501100011033 and European NextGeneration EU/PRTR and PRIMA programs to M.R.-C. (PID2023-149584NB-I00, PID2020-115810GB-I00, and UToPIQ-PCI2021-121941). M.R.-C. is also supported by Generalitat Valenciana (PROMETEU/2021/056 and AGROALNEXT/2022/067) and the MCIN/AEI-funded Spanish Carotenoid Network, CaRed (RED2022-134577-T). H.Z.'s visiting stay at IBMCP-Universitat Politecnica de Valencia was sponsored by the China Scholarship Council (CSC).Zheng, H.;Torres-Montilla, S.;Huang, X.;RODRIGUEZ-CONCEPCION, Manuel;Lu, S. (2025). STAY-GREEN overexpression in dark-incubated leaves promotes the formation of transitional chromoplast-like plastids. Plant Physiology. 198(2). https://doi.org/10.1093/plphys/kiaf242S198
Exploring the Deoxy-D-xylulose-5-phosphate Synthase Gene Family in Tomato (Solanum lycopersicum)
Get PDFIsoprenoids are a wide family of metabolites including high-value chemicals, flavors, pigments, and drugs. Isoprenoids are particularly abundant and diverse in plants. The methyl-D-erythritol 4-phosphate (MEP) pathway produces the universal isoprenoid precursors isopentenyl diphosphate and dimethylallyl diphosphate in plant plastids for the downstream production of monoterpenes, diterpenes, and photosynthesis-related isoprenoids such as carotenoids, chlorophylls, tocopherols, phylloquinone, and plastoquinone. The enzyme deoxy-D-xylulose 5-phosphate synthase (DXS) is the first and main rate-determining enzyme of the MEP pathway. In tomato (Solanum lycopersicum), a plant with an active isoprenoid metabolism in several tissues, three genes encode DXS-like proteins (SlDXS1 to 3). Here, we show that the expression patterns of the three genes suggest distinct physiological roles without excluding that they might function together in some tissues. We also confirm that SlDXS1 and 2 are true DXS enzymes, whereas SlDXS3 lacks DXS activity. We further show that SlDXS1 and 2 co-localize in plastidial speckles and that they can be immunoprecipitated together, suggesting that they might form heterodimers in vivo in at least some tissues. These results provide novel insights for the biotechnological use of DXS isoforms in metabolic engineering strategies to up-regulate the MEP pathway flux.This work was funded by grants PID2020-115810GB-I00 and UToPIQ-PCI2021-121941 from Spanish MCIN/AEI/10.13039/501100011033 and European NextGeneration EU/PRTR and PRIMA programs and PROMETEU/2021/056 and AGROALNEXT/2022/067 from Generalitat Valenciana to M.R.-C. X.D. was supported by the China Scholarship Council.Peer reviewe
A Chemical Probe for Increasing Leaf Tocopherol Levels by Coordinated Modulation of Biosynthesis, Competition and Storage
Get PDF[EN] Plant biofortification with phytonutrients typically relies on metabolic engineering strategies known as “push” (enhancing biosynthetic flux), “block” (inhibiting competing pathways), and “pull” (promoting metabolite storage). Here, we describe a novel synthetic compound, X57, that simultaneously targets biosynthesis, competition, and storage to enhance leaf tocopherol content. Tocopherols protect plants against oxidative stress, have dietary value as vitamin E, and are widely used as antioxidants in food and cosmetic formulations. X57 exerts a primary “push” effect by inducing tocopherol biosynthesis, partly through reactivating a direct pathway that reduces geranylgeranyl diphosphate (GGPP) to phytyl diphosphate, thereby bypassing the need for chlorophyll-derived phytol. Accordingly, X57 promotes tocopherol accumulation in etiolated seedlings and restores tocopherol synthesis in mutants deficient in phytol phosphorylation. The “block” effect is mediated by downregulation of GGPP consumption for carotenoid synthesis. X57 also induces a “pull” effect via proliferation of plastoglobules (PGs), plastidial lipoprotein bodies that synthesize and store tocopherols. X57-induced PG proliferation is driven by increased tocopherol levels and upregulation of genes encoding PG structural proteins such as fibrillins. The genetic networks coordinating plastidial isoprenoid metabolism and plastid differentiation may be specific to higher plants, as X57 does not promote—and instead reduces—tocopherol accumulation in Marchantia polymorpha.We thank Felix Kessler (University of Neuchatel) for the 35S:FBN7a-YFP line, Peter Dormann and Katharina Gutbrod (University of Bonn) for providing seeds of the vte5 mutants, and Miguel Angel Blazquez and Macarena Mellado-Sanchez (IBMCP) for providing Marchantia polymorpha thalli. We are also grateful to Jose M. Perez-Beser and Esther Pau-Ramos (IBMCP) for general technical support, Maria T. Minguez (University of Valencia SCSIE Microscopy Section) for her expert support with TEM, Javier Forment (IBMCP Bioinformatics platform) for his assistance with RNA-seq and BLAST analyses, and the IBMCP Metabolomics platform staff for help with HPLC.Pérez-Colao, Pablo;Glauser, G.;Cruces, J.;Lozano-Juste, Jorge;RODRIGUEZ-CONCEPCION, Manuel (2025). A Chemical Probe for Increasing Leaf Tocopherol Levels by Coordinated Modulation of Biosynthesis, Competition and Storage. Plant Biotechnology Journal. https://doi.org/10.1111/pbi.70459
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Arabidopsis FIBRILLIN6 influences carotenoid biosynthesis by directly promoting phytoene synthase activity
No full text© The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (https://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact [email protected] are health-promoting plastidial isoprenoids with essential functions in plants as photoprotectants and photosynthetic pigments in chloroplasts. They also accumulate in specialized plastids named chromoplasts, providing color to non-photosynthetic tissues such as flower petals and ripe fruit. Carotenoid accumulation in chromoplasts requires specialized structures and proteins such as fibrillins (FBNs). The FBN family includes structural components of carotenoid sequestering structures in chromoplasts and members with metabolic roles in chloroplasts and other plastid types. However, the association of FBNs with carotenoids in plastids other than chromoplasts has remained unexplored. Here, we show that Arabidopsis (Arabidopsis thaliana) FBN6 interacts with phytoene synthase (PSY), the first enzyme of the carotenoid pathway. FBN6, but not FBN4 (a FBN that does not interact with PSY), enhances the activity of plant PSY (but not of the bacterial PSY crtB) in Escherichia coli cells. Overexpression of FBN6 in Nicotiana benthamiana leaves results in a higher production of phytoene, the product of PSY activity, whereas loss of FBN6 activity in Arabidopsis mutants dramatically reduces the production of carotenoids during seedling de-etiolation and after exposure to high light. Our work hence demonstrates that FBNs promote not only the accumulation of carotenoids in chromoplasts but also their biosynthesis in chloroplasts.This work was funded by grants from Spanish MCIN/AEI/10.13039/501100011033 and European NextGeneration EU/PRTR and PRIMA programs to M.R.-C. (PID2020-115810GB-I00 and UToPIQ-PCI2021-121941). M.R.-C. is also supported by Generalitat Valenciana (PROMETEU/2021/056 and AGROALNEXT/2022/067). Our group is a member of CaRed (Spanish Carotenoid Network) funded by MCIN/AEI (RED2022-134577-T). A.I.-S. and J.N.-C. received predoctoral fellowships from MCIN/AEI (PRE2018-083610 and PRE2021-098681, respectively).Peer reviewe
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
