Publications by authors named "Sebastian Streb"

Article Synopsis
  • Microglia are special brain cells that help with brain health and development by cleaning up dead neurons.
  • In a disease called Niemann-Pick type C, microglia change shape and become less effective at their job when a protein called NPC1 is missing.
  • Researchers used zebrafish to show that without NPC1, microglia gather too much cholesterol and their “cleaning spots” get bigger, making them more sensitive to dying brain cells, which could help in understanding the disease better.
View Article and Find Full Text PDF

Amyotrophic lateral sclerosis (ALS) is a debilitating motor neuron disease and lacks effective disease-modifying treatments. This study utilizes a comprehensive multiomic approach to investigate the early and sex-specific molecular mechanisms underlying ALS. By analyzing the prefrontal cortex of 51 patients with sporadic ALS and 50 control subjects, alongside four transgenic mouse models (C9orf72-, SOD1-, TDP-43-, and FUS-ALS), we have uncovered significant molecular alterations associated with the disease.

View Article and Find Full Text PDF

A new therapeutic approach using cell-derived nanovesicles (cdNVs) is offered here to overcome the lack of effective treatments for liver fibrosis, a reversible chronic liver disease. To achieve this goal the formation and purification of cdNVs from untreated, quiescent-like, or activated LX-2 cells, an immortalized human hepatic stellate cell (HSC) line with key features of transdifferentiated HSCs are established. Analysis of the genotype and phenotype of naïve and transdifferentiated LX-2 cells activated through transforming growth factor beta 1, following treatment with cdNVs, reveals a concentration-dependent fibrosis regression.

View Article and Find Full Text PDF

Cisgenesis, the genetic modification of a plant with genes from a sexually compatible plant, was used to confer fire blight resistance to the cultivar 'Gala Galaxy' by amendment of the resistance gene FB_MR5, resulting in the line C44.4.146.

View Article and Find Full Text PDF
Article Synopsis
  • Plastid metabolism is essential for both types of plant cells (photoautotrophic and heterotrophic), and the enzyme fructose-1,6-bisphosphate aldolase (FBA) plays a key role in the Calvin-Benson cycle within chloroplasts.
  • Three genes (AtFBA1-AtFBA3) in Arabidopsis encode different FBA isoforms, with FBA2 being the primary isoform contributing to leaf activity, while FBA3 is linked to heterotrophic tissues like roots.
  • Mutants lacking either FBA2 or FBA3 show growth deficiencies, and combining mutations in both leads to severe growth issues due to disrupted photoautotrophy and compromised nutrient transport.
View Article and Find Full Text PDF

The carbon isotopic composition (δC) of foliage is often used as proxy for plant performance. However, the effect of vs. supply on δC of leaf metabolites and respired CO is largely unknown.

View Article and Find Full Text PDF

The majority of cellular processes are carried out by protein complexes. Various size fractionation methods have previously been combined with mass spectrometry to identify protein complexes. However, most of these approaches lack the quantitative information which is required to understand how changes of protein complex abundance and composition affect metabolic fluxes.

View Article and Find Full Text PDF

Plants are constantly challenged in their natural environment by a range of changing conditions. We investigated the acclimation processes and adaptive plant responses to various long-term mild changes and compared them directly within one experimental set-up. Arabidopsis thaliana plants were grown in hydroponic culture for 10 d under controlled abiotic stress (15°C, 25°C, salt and osmotic) and in nutrient deficiency (nitrate and phosphate).

View Article and Find Full Text PDF

Isoamylases hydrolyse (1-6)-alpha-D-glucosidic linkages in starch and are involved in both starch granule formation and starch degradation. In plants, three isoamylase isoforms with distinct functions in starch synthesis (ISA1 and ISA2) and degradation (ISA3) have been described. Here, we created transgenic potato plants with simultaneously decreased expression of all three isoamylases using a chimeric RNAi construct targeting all three isoforms.

View Article and Find Full Text PDF

Global demand for higher crop yields and for more efficient utilization of agricultural products will grow over the next decades. Here, we present a new concept for boosting the carbohydrate content of plants, by channeling photosynthetically fixed carbon into a newly engineered glucose polymer pool. We transiently expressed the starch/glycogen synthases from either Saccharomyces cerevisiae or Cyanidioschyzon merolae, together with the starch branching enzyme from C.

View Article and Find Full Text PDF

Arabidopsis leaf chloroplasts typically contain five to seven semicrystalline starch granules. It is not understood how the synthesis of each granule is initiated or how starch granule number is determined within each chloroplast. An Arabidopsis mutant lacking the glucosyl-transferase, STARCH SYNTHASE 4 (SS4) is impaired in its ability to initiate starch granules; its chloroplasts rarely contain more than one large granule, and the plants have a pale appearance and reduced growth.

View Article and Find Full Text PDF

The major component of starch is the branched glucan amylopectin, the branching pattern of which is one of the key factors determining its ability to form semicrystalline starch granules. Here, we investigated the functions of different branching enzyme (BE) types by expressing proteins from maize (Zea mays BE2a), potato (Solanum tuberosum BE1), and Escherichia coli (glycogen BE [EcGLGB]) in Arabidopsis (Arabidopsis thaliana) mutant plants that are deficient in their endogenous BEs and therefore, cannot make starch. The expression of each of these three BE types restored starch biosynthesis to differing degrees.

View Article and Find Full Text PDF

The major component of starch is the branched glucan amylopectin. Structural features of amylopectin, such as the branching pattern and the chain length distribution, are thought to be key factors that enable it to form semicrystalline starch granules. We varied both structural parameters by creating Arabidopsis (Arabidopsis thaliana) mutants lacking combinations of starch synthases (SSs) SS1, SS2, and SS3 (to vary chain lengths) and the debranching enzyme ISOAMYLASE1-ISOAMYLASE2 (ISA; to alter branching pattern).

View Article and Find Full Text PDF

This study tested the interchangeability of enzymes in starch metabolism between dicotyledonous and monocotyledonous plant species. Amylopectin--a branched glucose polymer--is the major component of starch and is responsible for its semi-crystalline property. Plants synthesize starch with distinct amylopectin structures, varying between species and tissues.

View Article and Find Full Text PDF

Isoamylase-type debranching enzymes (ISAs) play an important role in determining starch structure. Amylopectin - a branched polymer of glucose - is the major component of starch granules and its architecture underlies the semi-crystalline nature of starch. Mutants of several species lacking the ISA1-subclass of isoamylase are impaired in amylopectin synthesis.

View Article and Find Full Text PDF

STARCH SYNTHASE4 (SS4) is required for proper starch granule initiation in Arabidopsis (Arabidopsis thaliana), although SS3 can partially replace its function. Unlike other starch-deficient mutants, ss4 and ss3/ss4 mutants grow poorly even under long-day conditions. They have less chlorophyll and carotenoids than the wild type and lower maximal rates of photosynthesis.

View Article and Find Full Text PDF

The branched glucans glycogen and starch are the most widespread storage carbohydrates in living organisms. The production of semicrystalline starch granules in plants is more complex than that of small, soluble glycogen particles in microbes and animals. However, the factors determining whether glycogen or starch is formed are not fully understood.

View Article and Find Full Text PDF

Starch is the major non-structural carbohydrate in plants. It serves as an important store of carbon that fuels plant metabolism and growth when they are unable to photosynthesise. This storage can be in leaves and other green tissues, where it is degraded during the night, or in heterotrophic tissues such as roots, seeds and tubers, where it is stored over longer time periods.

View Article and Find Full Text PDF

In this study, we investigated which enzymes are involved in debranching amylopectin during transient starch degradation. Previous studies identified two debranching enzymes, isoamylase 3 (ISA3) and limit dextrinase (LDA), involved in this process. However, plants lacking both enzymes still degrade substantial amounts of starch.

View Article and Find Full Text PDF

Starch is a primary product of photosynthesis in the chloroplasts of many higher plants. It plays an important role in the day-to-day carbohydrate metabolism of the leaf, and its biosynthesis and degradation represent major fluxes in plant metabolism. Starch serves as a transient reserve of carbohydrate which is used to support respiration, metabolism, and growth at night when there is no production of energy and reducing power through photosynthesis, and no net assimilation of carbon.

View Article and Find Full Text PDF

Cytosolic phosphoglucomutase (cPGM) interconverts glucose-6-phosphate and glucose-1-phosphate and is a key enzyme of central metabolism. In this study, we show that Arabidopsis (Arabidopsis thaliana) has two cPGM genes (PGM2 and PGM3) encoding proteins with high sequence similarity and redundant functions. Whereas pgm2 and pgm3 single mutants were undistinguishable from the wild type, loss of both PGM2 and PGM3 severely impaired male and female gametophyte function.

View Article and Find Full Text PDF

Trees need to store reserves to allow their survival during winter and for bud flush and leaf growth in the following spring. In many tree species, these reserve functions are mainly covered by starch, which is degraded to soluble carbohydrates during the dormant season for maintenance respiration and in spring during bud flush. We conducted girdling experiments on poplar (Populus deltoides x nigra cv.

View Article and Find Full Text PDF

A putative phosphatase, LSF1 (for LIKE SEX4; previously PTPKIS2), is closely related in sequence and structure to STARCH-EXCESS4 (SEX4), an enzyme necessary for the removal of phosphate groups from starch polymers during starch degradation in Arabidopsis (Arabidopsis thaliana) leaves at night. We show that LSF1 is also required for starch degradation: lsf1 mutants, like sex4 mutants, have substantially more starch in their leaves than wild-type plants throughout the diurnal cycle. LSF1 is chloroplastic and is located on the surface of starch granules.

View Article and Find Full Text PDF