1,721,172 research outputs found
A plant secretory signal peptide targets plastome-encoded recombinant proteins to the thylakoid membrane
No full textPlastids are considered promising bioreactors
for the production of recombinant proteins, but the knowledge
of the mechanisms regulating foreign protein folding,
targeting, and accumulation in these organelles is still
incomplete. Here we demonstrate that a plant secretory
signal peptide is able to target a plastome-encoded recombinant
protein to the thylakoid membrane. The fusion protein
zeolin with its native signal peptide expressed by
tobacco (Nicotiana tabacum) transplastomic plants was
directed into the chloroplast thylakoid membranes, whereas
the zeolin mutant devoid of the signal peptide, Dzeolin, is
instead accumulated in the stroma. We also show that zeolin
folds in the thylakoid membrane where it accumulates as
trimers able to form disulphide bonds. Disulphide bonds
contribute to protein accumulation since zeolin shows a
higher accumulation level with respect to stromal Dzeolin,
whose folding is hampered as the protein accumulates at
low amounts in a monomeric form and it is not oxidized.
Thus, post-transcriptional processes seem to regulate the
stability and accumulation of plastid-synthesized zeolin.
The most plausible zeolin targeting mechanism to thylakoid
is discussed herein
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Expression of recombinant proteins in transformed plant chloroplasts is strictly regulated by protein quality control
No full textTraffic of human α-mannosidase in plant cells suggests the presence of a new endoplasmic reticulum-to-vacuole pathway without involving the Golgi complex
No full textThe transport of secretory proteins from the endoplasmic reticulum to the vacuole requires sorting signals as well as specific transport mechanisms. This work is focused on the transport in transgenic tobacco (Nicotiana tabacum) plants of a human a-mannosidase, MAN2B1, which is a lysosomal enzyme involved in the turnover of N-linked glycoproteins and can be used in enzyme replacement therapy. Although ubiquitously expressed, α-mannosidases are targeted to lysosomes or vacuoles through different mechanisms according to the organisms in which these proteins are produced. In tobacco cells, MAN2B1 reaches the vacuole even in the absence of mannose-6-phosphate receptors, which are responsible for its transport in animal cells. We report that MAN2B1 is targeted to the vacuole without passing through the Golgi complex. In addition, a vacuolar targeting signal that is recognized in plant cells is located in the MAN2B1 amino-terminal region. Indeed, when this amino-terminal domain is removed, the protein is retained in the endoplasmic reticulum. Moreover, when this domain is added to a plantsecreted protein, the resulting fusion protein is partially redirected to the vacuole. These results strongly suggest the existence in plants of a new type of vacuolar traffic that can be used by leaf cells to transport vacuolar protein
Phaseolin expression in tobacco chloroplast reveals an autoregulatory mechanism in heterologous protein translation
Full text linkPlastid DNA engineering is a well-established research area of plant biotechnology, and plastid transgenes often give high expression levels. However, it is still almost impossible to predict the accumulation rate of heterologous protein in transplastomic plants, and there are many cases of unsuccessful transgene expression. Chloroplasts regulate their proteome at the post-transcriptional level, mainly through translation control. One of the mechanisms to modulate the translation has been described in plant chloroplasts for the chloroplast-encoded subunits of multiprotein complexes, and the autoregulation of the translation initiation of these subunits depends on the availability of their assembly partners [control by epistasy of synthesis (CES)]. In Chlamydomonas reinhardtii, autoregulation of endogenous proteins recruited in the assembly of functional complexes has also been reported. In this study, we revealed a self-regulation mechanism triggered by the accumulation of a soluble recombinant protein, phaseolin, in the stroma of chloroplast-transformed tobacco plants. Immunoblotting experiments showed that phaseolin could avoid this self-regulation mechanism when targeted to the thylakoids in transplastomic plants. To inhibit the thylakoid-targeted phaseolin translation as well, this protein was expressed in the presence of a nuclear version of the phaseolin gene with a transit peptide. Pulse-chase and polysome analysis revealed that phaseolin mRNA translation on plastid ribosomes was repressed due to the accumulation in the stroma of the same soluble polypeptide imported from the cytosol. We suggest that translation autoregulation in chloroplast is not limited to heteromeric protein subunits but also involves at least some of the foreign soluble recombinant proteins, leading to the inhibition of plastome-encoded transgene expression in chloroplast
Obtainment of fertile and genetically stable transplastomic sugar beet plants over three generations
No full textInstitutional cooperation in handling epidemics: The case of the Misericordia of Florence during the Italian preunification period
No full textThe function of nonprofit organisations (NPOs) in managing healthcare and poverty relief and the role of accounting and reporting in their management control systems have many implications for accounting historians. The present research examines the relationship between NPOs and local governments in the management of public services, particularly during health emergencies. Specifically, this study examines the institutional cooperation between the Grand Duchy of Tuscany, the Misericordia of Florence and the Santa Maria Nuova Public Hospital during the cholera epidemic of 1855–1862. This research applies a conceptual framework based on Michel Foucault’s concepts of ‘governmentality’, ‘nosopolitics’ and the ‘government of the poor’ and Mitchell Dean’s ‘technologies of government’ to the study of archival primary sources. This research makes several contributions to the accounting history literature regarding the involvement of NPOs in healthcare, including an original analysis of the role of accounting and reporting in the ‘government of the sick’ from a nosopolitical perspective
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