The Vacuolar Inositol Transporter BvINT1;1 Contributes to Raffinose Biosynthesis and Reactive Oxygen Species Scavenging During Cold Stress in Sugar Beet.

Despite a high sucrose accumulation in its taproot vacuoles, sugar beet (Beta vulgaris subsp. vulgaris) is sensitive to freezing. Earlier, a taproot-specific accumulation of raffinose was shown to have beneficial effects on the freezing tolerance of the plant.

Overexpression of REDUCED WALL ACETYLATION C increases xylan acetylation and biomass recalcitrance in Populus.

Plant lignocellulosic biomass, i.e. secondary cell walls of plants, is a vital alternative source for bioenergy.

Multi-omics data integration reveals link between epigenetic modifications and gene expression in sugar beet (Beta vulgaris subsp. vulgaris) in response to cold.

Background: DNA methylation is thought to influence the expression of genes, especially in response to changing environmental conditions and developmental changes. Sugar beet (Beta vulgaris ssp. vulgaris), and other biennial or perennial plants are inevitably exposed to fluctuating temperatures throughout their lifecycle and might even require such stimulus to acquire floral competence.

Cold-Triggered Induction of ROS- and Raffinose Metabolism in Freezing-Sensitive Taproot Tissue of Sugar Beet.

Sugar beet ( subsp. ) is the exclusive source of sugar in the form of sucrose in temperate climate zones. Sugar beet is grown there as an annual crop from spring to autumn because of the damaging effect of freezing temperatures to taproot tissue.

Vernalization Alters Sink and Source Identities and Reverses Phloem Translocation from Taproots to Shoots in Sugar Beet.

During their first year of growth, overwintering biennial plants transport Suc through the phloem from photosynthetic source tissues to storage tissues. In their second year, they mobilize carbon from these storage tissues to fuel new growth and reproduction. However, both the mechanisms driving this shift and the link to reproductive growth remain unclear.

Mediation of plant-mycorrhizal interaction by a lectin receptor-like kinase.

The molecular mechanisms underlying mycorrhizal symbioses, the most ubiquitous and impactful mutualistic plant-microbial interaction in nature, are largely unknown. Through genetic mapping, resequencing and molecular validation, we demonstrate that a G-type lectin receptor-like kinase (lecRLK) mediates the symbiotic interaction between Populus and the ectomycorrhizal fungus Laccaria bicolor. This finding uncovers an important molecular step in the establishment of symbiotic plant-fungal associations and provides a molecular target for engineering beneficial mycorrhizal relationships.

Simultaneous knockdown of six non-family genes using a single synthetic RNAi fragment in Arabidopsis thaliana.

Background: Genetic engineering of plants that results in successful establishment of new biochemical or regulatory pathways requires stable introduction of one or more genes into the plant genome. It might also be necessary to down-regulate or turn off expression of endogenous genes in order to reduce activity of competing pathways. An established way to knockdown gene expression in plants is expressing a hairpin-RNAi construct, eventually leading to degradation of a specifically targeted mRNA.

Identification of Early Nuclear Target Genes of Plastidial Redox Signals that Trigger the Long-Term Response of Arabidopsis to Light Quality Shifts.

Natural illumination conditions are highly variable and because of their sessile life style, plants are forced to acclimate to them at the cellular and molecular level. Changes in light intensity or quality induce changes in the reduction/oxidation (redox) state of the photosynthetic electron chain that acts as a trigger for compensatory acclimation responses comprising functional and structural adjustments of photosynthesis and metabolism. Such responses include redox-controlled changes in plant gene expression in the nucleus and organelles.

Arabidopsis receptor of activated C kinase1 phosphorylation by WITH NO LYSINE8 KINASE.

Receptor of activated C kinase1 (RACK1) is a versatile scaffold protein that binds to numerous proteins to regulate diverse cellular pathways in mammals. In Arabidopsis (Arabidopsis thaliana), RACK1 has been shown to regulate plant hormone signaling, stress responses, and multiple processes of growth and development. However, little is known about the molecular mechanism underlying these regulations.

Characterization of MORE AXILLARY GROWTH genes in Populus.

Background: Strigolactones are a new class of plant hormones that play a key role in regulating shoot branching. Studies of branching mutants in Arabidopsis, pea, rice and petunia have identified several key genes involved in strigolactone biosynthesis or signaling pathway. In the model plant Arabidopsis, MORE AXILLARY GROWTH1 (MAX1), MAX2, MAX3 and MAX4 are four founding members of strigolactone pathway genes.

Strigolactone-regulated proteins revealed by iTRAQ-based quantitative proteomics in Arabidopsis.

Strigolactones (SLs) are a new class of plant hormones. In addition to acting as a key inhibitor of shoot branching, SLs stimulate seed germination of root parasitic plants and promote hyphal branching and root colonization of symbiotic arbuscular mycorrhizal fungi. They also regulate many other aspects of plant growth and development.

A dual role of strigolactones in phosphate acquisition and utilization in plants.

Phosphorus, acquired in the form of phosphate (Pi), is one of the primary macronutrients for plants but is least available in the soil. Pi deficiency is a major factor limiting plant growth, development and reproduction. Plants have developed a complex signaling network to respond to Pi deficiency.

New insights in the topology of the biosynthesis of 5-aminolevulinic acid.

The formation of 5-aminolevulinic acid (ALA) at the beginning of the pathway is the rate limiting step of tetrapyrrole biosynthesis and target of multiple timely and spatially organized control mechanisms. Recent discovery of a glutamyl-tRNA reductase-binding protein (GluTRBP), reveals a new insight in the topology of regulation of plant ALA biosynthesis.

Evidence for a Contribution of ALA Synthesis to Plastid-To-Nucleus Signaling.

The formation of 5-aminolevulinic acid (ALA) in tetrapyrrole biosynthesis is widely controlled by environmental and metabolic feedback cues that determine the influx into the entire metabolic path. Because of its central role as the rate-limiting step, we hypothesized a potential role of ALA biosynthesis in tetrapyrrole-mediated retrograde signaling and exploited the direct impact of ALA biosynthesis on nuclear gene expression (NGE) by using two different approaches. Firstly, the Arabidopsisgun1, hy1 (gun2), hy2 (gun3), gun4 mutants showing uncoupled NGE from the physiological state of chloroplasts were thoroughly examined for regulatory modifications of ALA synthesis and transcriptional control in the nucleus.

LCAA, a novel factor required for magnesium protoporphyrin monomethylester cyclase accumulation and feedback control of aminolevulinic acid biosynthesis in tobacco.

Low Chlorophyll Accumulation A (LCAA) antisense plants were obtained from a screen for genes whose partial down-regulation results in a strong chlorophyll deficiency in tobacco (Nicotiana tabacum). The LCAA mutants are affected in a plastid-localized protein of unknown function, which is conserved in cyanobacteria and all photosynthetic eukaryotes. They suffer from drastically reduced light-harvesting complex (LHC) contents, while the accumulation of all other photosynthetic complexes per leaf area is less affected.

Post-translational control of tetrapyrrole biosynthesis in plants, algae, and cyanobacteria.

The tetrapyrrole biosynthetic pathway provides the vital cofactors and pigments for photoautotrophic growth (chlorophyll), several essential redox reactions in electron transport chains (haem), N- and S-assimilation (sirohaem), and photomorphogenic processes (phytochromobilin). While the biochemistry of the pathway is well understood and almost all genes encoding enzymes of tetrapyrrole biosynthesis have been identified in plants, the post-translational control and organization of the pathway remains to be clarified. Post-translational mechanisms controlling metabolic activities are of particular interest since tetrapyrrole biosynthesis needs adaptation to environmental challenges.

An Arabidopsis GluTR binding protein mediates spatial separation of 5-aminolevulinic acid synthesis in chloroplasts.

5-Aminolevulinic acid (ALA) is the universal precursor for tetrapyrrole biosynthesis and is synthesized in plants in three enzymatic steps: ligation of glutamate (Glu) to tRNA(Glu) by glutamyl-tRNA synthetase, reduction of activated Glu to Glu-1-semialdehyde by glutamyl-tRNA reductase (GluTR), and transamination to ALA by Glu 1-semialdehyde aminotransferase. ALA formation controls the metabolic flow into the tetrapyrrole biosynthetic pathway. GluTR is proposed to be the key regulatory enzyme that is tightly controlled at transcriptional and posttranslational levels.

Methods for analysis of photosynthetic pigments and steady-state levels of intermediates of tetrapyrrole biosynthesis.

Tetrapyrroles and carotenoids are required for many indispensable functions in photosynthesis. Tetrapyrroles are essential metabolites for photosynthesis, redox reaction, and detoxification of reactive oxygen species and xenobiotics, while carotenoids function as accessory pigments, in photoprotection and in attraction to animals. Their branched metabolic pathways of synthesis and degradation are tightly controlled to provide adequate amounts of each metabolite (carotenoids/tetrapyrroles) and to prevent accumulation of photoreactive intermediates (tetrapyrroles).

Rapid dark repression of 5-aminolevulinic acid synthesis in green barley leaves.

In photosynthetic organisms chlorophyll and heme biosynthesis is tightly regulated at various levels in response to environmental adaptation and plant development. The formation of 5-aminolevulinic acid (ALA) is the key regulatory step and provides adequate amounts of the common precursor molecule for the Mg and Fe branches of tetrapyrrole biosynthesis. Pathway control prevents accumulation of metabolic intermediates and avoids photo-oxidative damage.

Expression of chlorophyll synthase is also involved in feedback-control of chlorophyll biosynthesis.

At the last step of the chlorophyll biosynthetic pathway chlorophyll synthase (CHLG) esterifies chlorophyllide a and b with phytyl or geranyl-geranyl pyrophosphate in chloroplasts. Transgenic tobacco plants expressing CHLG RNA in sense and antisense orientation were examined for the effects of excessive and reduced ectopic CHLG expression, respectively, on the chlorophyll biosynthetic pathway and the expression of chlorophyll-binding proteins. Reduced chlorophyll synthase activity does not result in accumulation of chlorophyllide and caused reduced ALA formation and Mg and ferrochelatase activity, while CHLG overexpression correlated with enhanced ALA synthesizing capacity and more chelatase activities.

Identification of peptide metabolites of Microcystis (Cyanobacteria) that inhibit trypsin-like activity in planktonic herbivorous Daphnia (Cladocera).

Cyanobacteria are recognized as producers of a broad variety of bioactive metabolites. Among these, the peptides synthesized by the non-ribosomal peptide synthetase pathway occur in high structural variability. One class of cyanobacterial peptides, the cyanopeptolins or micropeptins, have been shown to be strong inhibitors of vertebrate serine proteases, like trypsin.

Isolation, characterization, and quantitative analysis of Microviridin J, a new Microcystis metabolite toxic to Daphnia.

This paper describes the purification and characterization of microviridin J. a newly discovered metabolite of Microcystis that causes a lethal molting disruption in Daphnia spp., upon ingestion of living cyanobacterial cells.