Biomass to green surfactants: Microwave-assisted transglycosylation of wheat bran for alkyl glycosides production.

Depolymerization of carbohydrate biomass using a long-chain alcohol (transglycosylation) to produce alkyl glycoside-based bio-surfactants has been gaining industrial interest. This study introduces microwave-assisted transglycosylation in transforming wheat bran, a substantial agricultural side stream, into these valuable compounds. Compared to traditional heating, microwave-assisted processing significantly enhances the product yield by 53 % while reducing the reaction time by 72 %, achieving a yield of 29 % within 5 h. This enhancement results from the microwave's capacity to activate intermolecular hydrogen and glycosidic bonds, thereby facilitating transglycosylation. Life-cycle assessment and techno-economic analysis demonstrate the benefits of microwave heating in reducing energy consumption by 42 %, CO2 emissions by 56 %, and equipment, operational and production costs by 44 %, 35 % and 30 %, respectively. The study suggests that microwave heating is a promising approach for efficiently producing bio-surfactants from agricultural wastes, with potential cost reductions and environmental benefits that could enhance industrial biomass conversion processes.

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with ß-ketoesters and ß-ketoamides.

Two regiodivergent approaches to intermolecular cyclization of 2-aminobenzothiazoles with ß-ketoesters and amides have been developed, controlled by the reagents employed. With the Brønsted base KOt-Bu and CBrCl3 as radical initiator, benzo[d]imidazo[2,1-b]thiazoles are synthesized via attack at the α-carbon and keto carbon of the ß-ketoester moiety. In contrast, switching to the Lewis acid catalyst, In(OTf)3, results in the regioselective nucleophilic attack at both carbonyl groups forming benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones instead.

Synthesis of Disubstituted 3-Phenylimidazo[1,2-a]pyridines via a 2-Aminopyridine/CBrCl3 α-Bromination Shuttle.

A versatile protocol for the synthesis of disubstituted 3-phenylimidazo[1,2-a]pyridines by coupling 2-aminopyridine with phenylacetophenones, phenylacetones, or ß-tetralone has been developed. Isolated yields of up to 97% were obtained at 80 °C within 5 h. The 2-aminopyridine/CBrCl3 system acts as an α-bromination shuttle by transferring Br from CBrCl3 to the α-carbon of the carbonyl moiety. This triggers a series of steps with double C-N/C-N bond formation to the final product. The distinct advantages of this protocol include the use of commercially available inexpensive substrates, simplicity of a metal-free one-pot synthesis, and ease of scale-up to multigram quantities.

The role of miR156/SPLs modules in Arabidopsis lateral root development.

miR156 is an evolutionarily highly conserved miRNA in plants that defines an age-dependent flowering pathway. The investigations thus far have largely, if not exclusively, confined to plant aerial organs. Root branching architecture is a major determinant of water and nutrients uptake for plants. We show here that MIR156 genes are differentially expressed in specific cells/tissues of lateral roots. Plants overexpressing miR156 produce more lateral roots whereas reducing miR156 levels leads to fewer lateral roots. We demonstrate that at least one representative from the three groups of miR156 targets SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes: SPL3, SPL9 and SPL10 are involved in the repression of lateral root growth, with SPL10 playing a dominant role. In addition, both MIR156 and SPLs are responsive to auxin signaling suggesting that miR156/SPL modules might be involved in the proper timing of the lateral root developmental progression. Collectively, these results unravel a role for miR156/SPLs modules in lateral root development in Arabidopsis.

The Nitrosopumilus maritimus CdvB, but not FtsZ, assembles into polymers.

Euryarchaeota and Crenarchaeota are two major phyla of archaea which use distinct molecular apparatuses for cell division. Euryarchaea make use of the tubulin-related protein FtsZ, while Crenarchaea, which appear to lack functional FtsZ, employ the Cdv (cell division) components to divide. Ammonia oxidizing archaeon (AOA) Nitrosopumilus maritimus belongs to another archaeal phylum, the Thaumarchaeota, which has both FtsZ and Cdv genes in the genome. Here, we used a heterologous expression system to characterize FtsZ and Cdv proteins from N. maritimus by investigating the ability of these proteins to form polymers. We show that one of the Cdv proteins in N. maritimus, the CdvB (Nmar_0816), is capable of forming stable polymers when expressed in fission yeast. The N. maritimus CdvB is also capable of assembling into filaments in mammalian cells. However, N. maritimus FtsZ does not assemble into polymers in our system. The ability of CdvB, but not FtsZ, to polymerize is consistent with a recent finding showing that several Cdv proteins, but not FtsZ, localize to the mid-cell site in the dividing N. maritimus. Thus, we propose that it is Cdv proteins, rather than FtsZ, that function as the cell division apparatus in N. maritimus.

A matrix protein silences transposons and repeats through interaction with retinoblastoma-associated proteins.

Epigenetic regulation helps to maintain genomic integrity by suppressing transposable elements (TEs) and also controls key developmental processes, such as flowering time. To prevent TEs from causing rearrangements and mutations, TE and TE-like repetitive DNA sequences are usually methylated, whereas histones are hypoacetylated and methylated on specific residues (e.g., H3 lysine 9 dimethylation [H3K9me2]). TEs and repeats can also attenuate gene expression. However, how various histone modifiers are recruited to target loci is not well understood. Here we show that knockdown of the nuclear matrix protein with AT-hook DNA binding motifs TRANSPOSABLE ELEMENT SILENCING VIA AT-HOOK (TEK) in Arabidopsis Landsberg erecta results in robust activation of various TEs, the TE-like repeat-containing floral repressor genes FLOWERING LOCUS C (FLC) and FWA. This derepression is associated with chromatin conformational changes, increased histone acetylation, reduced H3K9me2, and even TE transposition. TEK directly binds to an FLC-repressive regulatory region and the silencing repeats of FWA and associates with Arabidopsis homologs of the Retinoblastoma-associated protein 46/48, FVE and MSI5, which mediate histone deacetylation. We propose that the nuclear matrix protein TEK acts in the maintenance of genome integrity by silencing TE and repeat-containing genes.

Comparing contractile apparatus-driven cytokinesis mechanisms across kingdoms.

Cytokinesis is the final stage of the cell cycle during which a cell physically divides into two daughters through the assembly of new membranes (and cell wall in some cases) between the forming daughters. New membrane assembly can either proceed centripetally behind a contractile apparatus, as in the case of prokaryotes, archaea, fungi, and animals or expand centrifugally, as in the case of higher plants. In this article, we compare the mechanisms of cytokinesis in diverse organisms dividing through the use of a contractile apparatus. While an actomyosin ring participates in cytokinesis in almost all centripetally dividing eukaryotes, the majority of bacteria and archaea (except Crenarchaea) divide using a ring composed of the tubulin-related protein FtsZ. Curiously, despite molecular conservation of the division machinery components, division site placement and its cell cycle regulation occur by a variety of unrelated mechanisms even among organisms from the same kingdom. While molecular motors and cytoskeletal polymer dynamics contribute to force generation during eukaryotic cytokinesis, cytoskeletal polymer dynamics alone appears to be sufficient for force generation during prokaryotic cytokinesis. Intriguingly, there are life forms on this planet that appear to lack molecules currently known to participate in cytokinesis and how these cells perform cytokinesis remains a mystery waiting to be unravelled.

AGAMOUS controls GIANT KILLER, a multifunctional chromatin modifier in reproductive organ patterning and differentiation.

The Arabidopsis homeotic protein AGAMOUS (AG), a MADS domain transcription factor, specifies reproductive organ identity during flower development. Using a binding assay and expression analysis, we identified a direct target of AG, GIANT KILLER (GIK), which fine-tunes the expression of multiple genes downstream of AG. The GIK protein contains an AT-hook DNA binding motif that is widely found in chromosomal proteins and that binds to nuclear matrix attachment regions of DNA elements. Overexpression and loss of function of GIK cause wide-ranging defects in patterning and differentiation of reproductive organs. GIK directly regulates the expression of several key transcriptional regulators, including ETTIN/AUXIN RESPONSE FACTOR 3 (ETT/ARF3) that patterns the gynoecium, by binding to the matrix attachment regions of target promoters. Overexpression of GIK causes a swift and dynamic change in repressive histone modification in the ETT promoter. We propose that GIK acts as a molecular node downstream of the homeotic protein AG, regulating patterning and differentiation of reproductive organs through chromatin organization.

A timing mechanism for stem cell maintenance and differentiation in the Arabidopsis floral meristem.

Developmental regulation of the floral meristem ensures that plants of the same species have similarly sized flowers with a fixed number of floral organs. The maintenance of stem cells in the floral meristem is terminated after the production of a fixed number of floral organ primordia. Precise repression of the Arabidopsis thaliana homeobox gene WUSCHEL (WUS) by the floral homeotic protein AGAMOUS (AG) plays a major part in this process. Here we show that KNUCKLES (KNU) mediates the repression of WUS in floral meristem determinacy control. AG directly induces the transcription of KNU, which encodes a C2H2-type zinc finger protein with a conserved transcriptional repression motif. In turn, KNU represses WUS transcription to abolish stem cell activity. We also show that the timing of KNU induction is key in balancing proliferation and differentiation in flower development. Delayed KNU expression results in an indeterminate meristem, whereas ectopic KNU expression prematurely terminates the floral meristem. Furthermore, KNU induction by AG is preceded by changes in repressive histone modification at the KNU locus, which occurs in an AG-dependent manner. This study provides a mechanistic link between transcriptional feedback and epigenetic regulation in plant stem cell proliferation.

The homeotic protein AGAMOUS controls late stamen development by regulating a jasmonate biosynthetic gene in Arabidopsis.

The Arabidopsis thaliana floral homeotic gene AGAMOUS (AG) plays a central role in reproductive organ (stamen and carpel) development. AG RNA is expressed in the center of floral primordia from a time prior to the initiation of stamen and carpel primordia until late in flower development. While early AG expression acts in specification of stamens and carpels, the role, if any, of continued AG expression in later flower development is unknown. To examine the timing of AG action and its possible late-stage functions, we performed a series of time-course experiments using a transgenic line with inducible AG activity in an ag homozygous mutant background. We show that AG controls late-stage stamen development, including anther morphogenesis and dehiscence, as well as filament formation and elongation. We further show that AG coordinates late stamen maturation by controlling a biosynthetic gene of the lipid-derived phytohormone jasmonic acid (JA). Expression analysis and in vivo binding of AG indicate that AG directly regulates the transcription of a catalytic enzyme of JA, DEFECTIVE IN ANTHER DEHISCENCE1. Our results indicate that stamen identity and differentiation control by AG is achieved by the regulation of different transcriptional cascades in different floral stages, with organ specification induced early, followed by phytohormone biosynthesis to coordinate stamen maturation.

Ric-8 controls Drosophila neural progenitor asymmetric division by regulating heterotrimeric G proteins.

Asymmetric division of Drosophila neuroblasts (NBs) and the Caenorhabditis elegans zygote uses polarity cues provided by the Par proteins, as well as heterotrimeric G-protein-signalling that is activated by a receptor-independent mechanism mediated by GoLoco/GPR motif proteins. Another key component of this non-canonical G-protein activation mechanism is a non-receptor guanine nucleotide-exchange factor (GEF) for Galpha, RIC-8, which has recently been characterized in C. elegans and in mammals. We show here that the Drosophila Ric-8 homologue is required for asymmetric division of both NBs and pl cells. Ric-8 is necessary for membrane targeting of Galphai, Pins and Gbeta13F, presumably by regulating multiple Galpha subunit(s). Ric-8 forms an in vivo complex with Galphai and interacts preferentially with GDP-Galphai, which is consistent with Ric-8 acting as a GEF for Galphai. Comparisons of the phenotypes of Galphai, Ric-8, Gbeta13Fsingle and Ric-8;Gbeta13F double loss-of-function mutants indicate that, in NBs, Ric-8 positively regulates Gai activity. In addition, Gbetagamma acts to restrict Galphai (and GoLoco proteins) to the apical cortex, where Galphai (and Pins) can mediate asymmetric spindle geometry.

Sulfate conjugating and transport functions of MDCK distal tubular cells.

BACKGROUND: Transfected Madin-Darby canine kidney (MDCK) cells (of distal tubular origin) have been used to study transport of organic anions. These cells have not been shown to possess sulfate-conjugating activity. Neither has transport activity been demonstrated in nontransfected MDCK cells. METHODS: Polarized and monolayers of nontransfected MDCK type II cells were incubated with prototype substrates of phenolsulfotransferase (PST) and sodium sulfate in the absence or presence of known inhibitors of multidrug resistance protein (MRP): (3-3-(2-(7-chloro-2-quinionlinyl) ethenyl)phenyl)(3-dimethylamino-3-oxopropyl)thio)methyl)thio) propanoic acid (MK571), cyclosporin A (CsA), and probenecid. Effects of glutathione (GSH) and buthionine sulfoximine (BSO), potential modulators of the organic anion transporting protein/polypeptide (OATP) isoform, OATP1 were also examined. Sulfated conjugates were identified by high-performance liquid chromatography (HPLC)-radiometry or HPLC-fluorimetry. RESULTS: Uptake, sulfate conjugation, and efflux of the sulfated conjugates of harmol, p-nitrophenol, N-acetyldopamine and acetaminophen were demonstrated. Activities in MDCK type II cells were higher than those in HepG2, human fetal liver, and Chang liver cells. A significant decrease in extracellular with a reciprocal increase in intracellular harmol sulfate was observed with MK571, CsA, and probenecid and with preloading of glutathione. Depletion of intracellular glutathione by BSO had the opposite effects. CONCLUSIONS: Normal (nontransfected) MDCK type II cells provide a suitable system for the study of the physiologic processes of uptake, sulfate conjugation, and transport of sulfated conjugates in kidney cells. Based on the action of specific inhibitors and modulators of MRP2 and OATP1, it was concluded that MRP2-like and OATP1-like transporters are possibly responsible for the transport of sulfated conjugates.