1,720,957 research outputs found
Wax biosynthesis in response to danger: its regulation upon abiotic and biotic stress
No full textSummary The plant cuticle is the first physical barrier between land plants and their terrestrial environment. It consists of the polyester scaffold cutin embedded and sealed with organic, solvent‐extractable cuticular waxes. Cuticular wax ultrastructure and chemical composition differ with plant species, developmental stage and physiological state. Despite this complexity, cuticular wax consistently serves a critical role in restricting nonstomatal water loss. It also protects the plant against other environmental stresses, including desiccation, UV radiation, microorganisms and insects. Within the broader context of plant responses to abiotic and biotic stresses, our knowledge of the explicit roles of wax crystalline structures and chemical compounds is lacking. In this review, we summarize our current knowledge of wax biosynthesis and regulation in relation to abiotic and biotic stresses and stress responses.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165
Draft Genome Sequence of the Thermophilic Acetogen <i>Moorella humiferrea</i> DSM 23265
No full textABSTRACT
Moorella humiferrea
is an endospore-forming, anaerobic, and thermophilic bacterium which was isolated from a terrestrial hydrothermal spring.
M. humiferrea
is able to use humic acid or 10-anthraquinone-2,6-disulfonate as an electron-shuttling compound for growth and Fe(III) reduction. The genome has a size of 2.629 Mb and contains 2,668 predicted protein-coding genes.
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Ectopic expression of wax ester synthase under a wood-specific promoter enhances cell wall production and wood hydrophobicity
No full textAbstract Background Many industrial applications of wood and woody biomass require harsh physicochemical pretreatments to improve the hydrophobicity and durability of the products. Environmentally friendly wood biorefineries necessitate the replacement of chemicals and energy-consuming wood processing. Here, our goal was to increase wood hydrophobicity via the ectopic expression of Jojoba (Simmondsia chinensis) wax ester synthase (ScWS) in poplar (Populus × canescens). We expressed ScWS under a wood-specific promoter (DX15), which naturally controls the expression of FASCICLIN-like ARABINOGALACTAN PROTEIN 15 (FLA15) in the xylem. Results In the DX15::ScWS lines, ScWS was highly expressed in wood but not in leaves. The transgenic lines exhibited normal photosynthesis and growth similar to the wild-type poplars. Compared with the wild-type poplars, the DX15::ScWS lines accumulated greater amounts of triacylglycerol in wood and a greater number of lipid droplets in ray parenchyma cells. The composition of the bark cuticle wax esters was unaffected. The wood of the DX15::ScWS lines showed greater water repellency and less swelling than that of the wild-type poplars. Furthermore, the DX15::ScWS lines had an increased expression of FLA15 and increased cell wall deposition in fibers, resulting in increased wood density. Conclusions Our results highlight the potential of combining the wood-specific DX15 promoter with ScWS to enhance the technological properties of poplar wood. Reduced wood hydrophilicity represents a significant improvement in wood quality. In addition, our results suggest that the overexpression of the DX15 promoter could be a promising strategy for improving lignocellulose biomass in plants. Since poplars are highly productive species that can be cultivated in short-rotation plantations, our results have high translational potential for advancing sustainable wood utilization for a wider range of applications.Open-Access-Publikationsfonds 202
Divergent evolution of the alcohol‐forming pathway of wax biosynthesis among bryophytes
No full textSummary
The plant cuticle is a hydrophobic barrier, which seals the epidermal surface of most aboveground organs. While the cuticle biosynthesis of angiosperms has been intensively studied, knowledge about its existence and composition in nonvascular plants is scarce.
Here, we identified and characterized homologs of
Arabidopsis thaliana
fatty acyl‐CoA reductase (FAR) ECERIFERUM 4 (
At
CER4) and bifunctional wax ester synthase/acyl‐CoA:diacylglycerol acyltransferase 1 (
At
WSD1) in the liverwort
Marchantia polymorpha
(MpFAR2 and MpWSD1) and the moss
Physcomitrium patens
(PpFAR2A, PpFAR2B, and PpWSD1).
Although bryophyte harbor similar compound classes as described for angiosperm cuticles, their biosynthesis may not be fully conserved between the bryophytes
M. polymorpha
and
P. patens
or between these bryophytes and angiosperms. While PpFAR2A and PpFAR2B contribute to the production of primary alcohols in
P. patens
, loss of Mp
FAR2
function does not affect the wax profile of
M. polymorpha
. By contrast, MpWSD1 acts as the major wax ester‐producing enzyme in
M. polymorpha
, whereas mutations of Pp
WSD1
do not affect the wax ester levels of
P. patens
.
Our results suggest that the biosynthetic enzymes involved in primary alcohol and wax ester formation in land plants have either evolved multiple times independently or undergone pronounced radiation followed by the formation of lineage‐specific toolkits.Alexander von Humboldt-Stiftung https://doi.org/10.13039/100005156Natural Sciences and Engineering Research Council of Canada https://doi.org/10.13039/501100000038Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659National Research Foundation of Korea https://doi.org/10.13039/501100003725H2020 European Research Council https://doi.org/10.13039/10001066
The evolution of hydrophobic barriers among land plants
No full textThe terrestrialization of plants required major physiological and metabolic adaptations, including the capacity to deposit extracellular hydrophobic barriers that shield plant surfaces against various abiotic and biotic stresses. The plant cuticle covers the outermost primary surfaces of almost all aerial plant organs and is composed of the core scaffolding cutin and a mixture of cuticular waxes. In contrast, the biopolymer suberin is mainly associated with belowground tissues, controlling water and ion transport. Substantial progress has been made in understanding the molecular mechanisms of hydrophobic barrier formation in vascular plants, such as Arabidopsis thaliana. However, only a limited number of studies addressed the function of genetic orthologs involved in cuticle biosynthesis in bryophytes. While many of the gene families involved in cuticle biosynthesis are less represented in bryophytes, they gradually increased in gene numbers among vascular plants. To understand the origins and evolution of hydrophobic barriers among land plants, homologs of cuticle biosynthetic enzymes were characterized by reverse-genetic approaches in two model bryophyte species.
Furthermore, the role of the R2R3-type Myeloblastosis (MYB) transcription factor AtMYB41 in the formation of hydrophobic barriers has been studied throughout plant development. Previous reports implicated AtMYB41 in the regulation of cutin and endodermal suberin biosynthesis. Here, the characterization of an Atmyb41ge mutant collection has shown that AtMYB41 functions as a dual-function transcription factor of lipid metabolism. Thereby, AtMYB41 acts as a negative regulator of cuticle and fatty acid biosynthesis in leaves and seeds, respectively, but also as a positive regulator of wax production in A. thaliana stems.2025-05-2
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
No full textWe 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
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