Bacterial infection remains a serious threat to human lives because of emerging resistance to existing antibiotics. Although the scientific community has avidly pursued the discovery of new antibiotics that interact with new targets, these efforts have met with limited success since the early 1960s. Here we report the discovery of platensimycin, a previously unknown class of antibiotics produced by Streptomyces platensis. Platensimycin demonstrates strong, broad-spectrum Gram-positive antibacterial activity by selectively inhibiting cellular lipid biosynthesis. We show that this anti-bacterial effect is exerted through the selective targeting of beta-ketoacyl-(acyl-carrier-protein (ACP)) synthase I/II (FabF/B) in the synthetic pathway of fatty acids. Direct binding assays show that platensimycin interacts specifically with the acyl-enzyme intermediate of the target protein, and X-ray crystallographic studies reveal that a specific conformational change that occurs on acylation must take place before the inhibitor can bind. Treatment with platensimycin eradicates Staphylococcus aureus infection in mice. Because of its unique mode of action, platensimycin shows no cross-resistance to other key antibiotic-resistant strains tested, including methicillin-resistant S. aureus, vancomycin-intermediate S. aureus and vancomycin-resistant enterococci. Platensimycin is the most potent inhibitor reported for the FabF/B condensing enzymes, and is the only inhibitor of these targets that shows broad-spectrum activity, in vivo efficacy and no observed toxicity.

At high ambient temperature, plants display dramatic stem elongation in an adaptive response to heat. This response is mediated by elevated levels of the phytohormone auxin and requires auxin biosynthesis, signaling, and transport pathways. The mechanisms by which higher temperature results in greater auxin accumulation are unknown, however. A basic helix-loop-helix transcription factor, PHYTOCHROME-INTERACTING FACTOR 4 (PIF4), is also required for hypocotyl elongation in response to high temperature. PIF4 also acts redundantly with its homolog, PIF5, to regulate diurnal growth rhythms and elongation responses to the threat of vegetative shade. PIF4 activity is reportedly limited in part by binding to both the basic helix-loop-helix protein LONG HYPO-COTYL IN FAR RED 1 and the DELLA family of growth-repressing proteins. Despite the importance of PIF4 in integrating multiple environmental signals, the mechanisms by which PIF4 controls growth are unknown. Here we demonstrate that PIF4 regulates levels of auxin and the expression of key auxin biosynthesis genes at high temperature. We also identify a family of SMALL AUXIN UP RNA (SAUR) genes that are expressed at high temperature in a PIF4-dependent manner and promote elongation growth. Taken together, our results demonstrate direct molecular links among PIF4, auxin, and elongation growth at high temperature.indole-3-acetic acid | TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 | CYP79B2 T he hormone indole-3-acetic acid (IAA, or auxin) is fundamental to plant growth and development, controlling many key aspects of shoot and root growth (1). When plants are grown at elevated temperatures, IAA levels increase, resulting in increased hypocotyl elongation (2, 3). Although genetic studies in Arabidopsis have demonstrated that this growth response is dependent on auxin biosynthesis, signaling, and transport pathways, precisely how high temperature promotes an increase in auxin levels has not been established. There are multiple pathways for the de novo synthesis of IAA, the major naturally occurring plant auxin, which are often classified according to whether or not they require the precursor tryptophan (4). Although progress has been made in elucidating some of the enzymes involved in IAA biosynthesis, our understanding of these pathways and their regulation remains rudimentary.In addition to auxin, the basic helix-loop-helix transcription factor PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) is also required for temperature-dependent hypocotyl elongation (5, 6). PIF4 has emerged as a key regulator of elongation in response to external signals, such as temperature and light, as well as internal signals, including gibberellin and the circadian clock (7-12). In the present work, we investigated potential mechanistic links between PIF4 and IAA in the control of temperatureinduced hypocotyl elongation. We found that PIF4 promotes IAA biosynthesis, possibly by activating the expression of key IAA biosynthetic genes in a temperature-dependent manner. Results and DiscussionGiven that s...

The photothermal therapy using nanomaterials has been recently attracted as an efficient strategy for the next generation of cancer treatments. Single walled carbon nanotube (SWNT) is an upcoming potent candidate for the photothermal therapeutic agent since it generates significant amounts of heat upon excitation with near-infrared light (NIR, lambda = 700-1100 nm) which is transparent to biological systems including skins. Such a photothermal effect can be employed to induce thermal cell death in a noninvasive manner. Here, we demonstrate in vivo obliteration of solid malignant tumors by the combined treatments of SWNTs and NIR irradiation. The photothermally treated mice displayed complete destruction of the tumors without harmful side effects or recurrence of tumors over 6 months, while the tumors treated in other control groups were continuously grown until the death of the mice. Most of the injected SWNTs were almost completely excreted from mice bodies in about 2 months through biliary or urinary pathway. These results suggest that SWNTs may potentially serve as an effective photothermal agent and pave the way to future cancer therapeutics.

The plant hormone auxin promotes cell expansion. Forty years ago, the acid growth theory was proposed, whereby auxin promotes proton efflux to acidify the apoplast and facilitate the uptake of solutes and water to drive plant cell expansion. However, the underlying molecular and genetic bases of this process remain unclear. We have previously shown that the SAUR19-24 subfamily of auxin-induced SMALL AUXIN UP-RNA (SAUR) genes promotes cell expansion. Here, we demonstrate that SAUR proteins provide a mechanistic link between auxin and plasma membrane H + -ATPases

Emergence of bacterial resistance is a major issue for all classes of antibiotics; therefore, the identification of new classes is critically needed. Recently we reported the discovery of platensimycin by screening natural product extracts using a target-based whole-cell strategy with antisense silencing technology in concert with cell free biochemical validations. Continued screening efforts led to the discovery of platencin, a novel natural product that is chemically and biologically related but different from platensimycin. Platencin exhibits a broad-spectrum Gram-positive antibacterial activity through inhibition of fatty acid biosynthesis. It does not exhibit cross-resistance to key antibiotic resistant strains tested, including methicillin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus, and vancomycin-resistant Enterococci. Platencin shows potent in vivo efficacy without any observed toxicity. It targets two essential proteins, ␤-ketoacyl-[acyl carrier protein (ACP)] synthase II (FabF) and III (FabH) with IC 50 values of 1.95 and 3.91 g/ml, respectively, whereas platensimycin targets only FabF (IC 50 ‫؍‬ 0.13 g/ml) in S. aureus, emphasizing the fact that more antibiotics with novel structures and new modes of action can be discovered by using this antisense differential sensitivity wholecell screening paradigm.platensimycin ͉ natural product ͉ thiolactomycin ͉ antisense ͉ fatty acid synthesis

The temporal expression patterns of the critical Vibrio cholerae virulence genes, tcpA and ctxA, were determined during infection using a recombinase reporter. TcpA was induced biphasically in two temporally and spatially separable events in the small intestine, whereas ctxA was induced monophasically only after, and remarkably, dependent upon, tcpA expression; however, this dependence was not observed during in vitro growth. The requirements of the virulence regulators, ToxR, TcpP, and ToxT, for expression of tcpA and ctxA were determined and were found to differ significantly during infection versus during growth in vitro. These results illustrate the importance of examining virulence gene expression in the context of bona fide host-pathogen interactions.

Purpose The Cancer Genome Atlas (TCGA) project recently uncovered four molecular subtypes of gastric cancer: Epstein-Barr virus (EBV), microsatellite instability (MSI), genomically stable (GS), and chromosomal instability (CIN). However, their clinical significances are currently unknown. We aimed to investigate the relationship between subtypes and prognosis of patients with gastric cancer. Experimental Design Gene expression data from a TCGA cohort (n = 262) were used to develop a subtype prediction model, and the association of each subtype with survival and benefit from adjuvant chemotherapy was tested in 2 other cohorts (n = 267 and 432). An integrated risk assessment model (TCGA risk score) was also developed. Results EBV subtype was associated with the best prognosis and GS subtype was associated with the worst prognosis. Patients with MSI and CIN subtypes had poorer overall survival than those with EBV subtype but better overall survival than those with GS subtype (P = 0.004 and 0.03 in two cohorts respectively). In multivariate Cox regression analyses, TCGA risk score was an independent prognostic factor (hazard ratio [HR] = 1.5; 95% confidence interval [CI] = 1.2–1.9; P = 0.001). Patients with the CIN subtype experienced the greatest benefit from adjuvant chemotherapy (HR = 0.39; 95% CI = 0.16–0.94; P = 0.03) and those with the GS subtype had the least benefit from adjuvant chemotherapy (HR = 0.83; 95% CI = 0.36–1.89; P = 0.65). Conclusion Our prediction model successfully stratified patients by survival and adjuvant chemotherapy outcomes. Further development of the prediction model is warranted.

Though emerging evidence indicates that the pathogenesis of Parkinson's disease is strongly correlated to the accumulation and transmission of α-synuclein (α-syn) aggregates in the midbrain, no anti-aggregation agents have been successful at treating the disease in the clinic. Here, we show that graphene quantum dots (GQDs) inhibit fibrillization of α-syn and interact directly with mature fibrils, triggering their disaggregation. Moreover, GQDs can rescue neuronal death and synaptic loss, reduce Lewy body and Lewy neurite formation, ameliorate mitochondrial dysfunctions, and prevent neuron-to-neuron transmission of α-syn pathology provoked by α-syn preformed fibrils. We observe, in vivo, that GQDs penetrate the blood-brain barrier and protect against dopamine neuron loss induced by α-syn preformed fibrils, Lewy body/Lewy neurite pathology and behavioural deficits.