Salicylic acid (SA) is an essential hormone in plant immunity, but its receptor has remained elusive for decades. The transcriptional coregulator NPR1 is central to the activation of SA-dependent ...defense genes, and we previously found that Cys521 and Cys529 of Arabidopsis NPR1's transactivation domain are critical for coactivator function. Here, we demonstrate that NPR1 directly binds SA, but not inactive structural analogs, with an affinity similar to that of other hormone-receptor interactions and consistent with in vivo Arabidopsis SA concentrations. Binding of SA occurs through Cys521/529 via the transition metal copper. Mechanistically, our results suggest that binding of SA causes a conformational change in NPR1 that is accompanied by the release of the C-terminal transactivation domain from the N-terminal autoinhibitory BTB/POZ domain. While NPR1 is already known as a link between the SA signaling molecule and defense-gene activation, we now show that NPR1 is the receptor for SA.
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► NPR1 is a salicylic acid (SA) receptor, binding specifically to SA via Cys521/529 ► NPR1 binds copper in vivo via Cys521/529, and metals are required for SA binding ► SA directly regulates the conformation of NPR1 by deoligomerizing NPR1 into a dimer ► The NPR1 BTB/POZ domain autoinhibits the function of the NPR1 transactivation domain
Salicylic acid (SA) is a phytohormone involved in systemic acquired resistance, a type of plant immunity against pathogens. Its receptor has long eluded detection. Després and colleagues find that in Arabidopsis, the transcriptional coactivator, NPR1, is the SA receptor. Cysteines 521 and 529 of NPR1 and copper are required for ligand-receptor interactions. SA binding unveils a transactivation domain in NPR1, which, together with TGA2, activates the defense marker-gene, PR-1. This discovery fills a major knowledge gap between pathogen-triggered SA accumulation and defense gene activation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Iridoids are a major group of biologically active molecules that are present in thousands of plant species, and one versatile iridoid, secologanin, is a precursor for the assembly of thousands of ...monoterpenoid indole alkaloids (MIAs) as well as a number of quinoline alkaloids. This study uses bioinformatics to screen large databases of annotated transcripts from various MIA‐producing plant species to select candidate genes that may be involved in iridoid biosynthesis. Virus‐induced gene silencing of the selected genes combined with metabolite analyses of silenced plants was then used to identify the 7‐deoxyloganic acid 7‐hydroxylase (CrDL7H) that is involved in the 3rd to last step in secologanin biosynthesis. Silencing of CrDL7H reduced secologanin levels by at least 70%, and increased the levels of 7‐deoxyloganic acid to over 4 mg g⁻¹ fresh leaf weight compared to control plants in which this iridoid is not detected. Functional expression of this CrDL7H in yeast confirmed its biochemical activity, and substrate specificity studies showed its preference for 7‐deoxyloganic acid over other closely related substrates. Together, these results suggest that hydroxylation precedes carboxy‐O‐methylation in the secologanin pathway in Catharanthus roseus.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The orexin-A/hypocretin-1 and orexin-B/hypocretin-2 are neuropeptides synthesized by a cluster of neurons in the lateral hypothalamus and perifornical area. Orexin neurons receive a variety of ...signals related to environmental, physiological and emotional stimuli, and project broadly to the entire CNS. Orexin neurons are "multi-tasking" neurons regulating a set of vital body functions, including sleep/wake states, feeding behavior, energy homeostasis, reward systems, cognition and mood. Furthermore, a dysfunction of orexinergic system may underlie different pathological conditions. A selective loss orexin neurons was found in narcolepsia, supporting the crucial role of orexins in maintaining wakefulness. In animal models, orexin deficiency lead to obesity even if the consume of calories is lower than wildtype counterpart. Reduced physical activity appears the main cause of weight gain in these models resulting in energy imbalance. Orexin signaling promotes obesity resistance via enhanced spontaneous physical activity and energy expenditure regulation and the deficiency/dysfunction in orexins system lead to obesity in animal models despite of lower calories intake than wildtype associated with reduced physical activity. Interestingly, orexinergic neurons show connections to regions involved in cognition and mood regulation, including hippocampus. Orexins enhance hippocampal neurogenesis and improve spatial learning and memory abilities, and mood. Conversely, orexin deficiency results in learning and memory deficits, and depression.
The Madagascar periwinkle (Catharanthus roseus) is highly specialized for the biosynthesis of many different monoterpenoid indole alkaloids (MIAs), many of which have powerful biological activities. ...Such MIAs include the commercially important chemotherapy drugs vinblastine, vincristine, and other synthetic derivatives that are derived from the coupling of catharanthine and vindoline. However, previous studies have shown that biosynthesis of these MIAs involves extensive movement of metabolites between specialized internal leaf cells and the leaf epidermis that require the involvement of unknown secretory processes for mobilizing catharanthine to the leaf surface and vindoline to internal leaf cells. Spatial separation of vindoline and catharanthine provides a clear explanation for the low levels of dimers that accumulate in intact plants. The present work describes the molecular cloning and functional identification of a unique catharanthine transporter (CrTPT2) that is expressed predominantly in the epidermis of young leaves. CrTPT2 gene expression is activated by treatment with catharanthine, and its in planta silencing redistributes catharanthine to increase the levels of catharanthine–vindoline drug dimers in the leaves. Phylogenetic analysis shows that CrTPT2 is closely related to a key transporter involved in cuticle assembly in plants and that may be unique to MIA-producing plant species, where it mediates secretion of alkaloids to the plant surface.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Summary
The important anticancer drugs, vinblastine, vincristine and analogs, are composed of the monoterpenoid indole alkaloids (MIAs), catharanthine and vindoline, found uniquely in the medicinal ...plant, Catharanthus roseus. While 26 genes involved in the assembly of these two MIAs are known, two key reactions have eluded characterization to complete the documentation of the vinblastine pathway in this plant species. The assembly of these dimeric MIAs requires O‐acetylstemmadenine oxidase (ASO) and a dual function geissoschizine synthase (GS) that reduces cathenamine to form geissoschizine, and that also reduces the ASO product to form a common intermediate for subsequent conversion by four separate hydrolases to catharanthine, tabersonine or vincadifformine, respectively. The in planta role of ASO is supported by identifying a single amino acid‐substituted ASO mutant with very low enzyme activity and by virus‐induced gene silencing of ASO to produce plants that accumulate O‐acetylstemmadenine rather than catharanthine and vindoline found in wild‐type (WT) plants. The in planta role of GS is supported by showing that a low GS‐expressing mutant accumulating lower levels of catharanthine and vindoline also displays significantly lower tabersonine‐forming activity in coupled enzyme assays than in the WT background. Gene expression analyses demonstrate that both ASO and GS are highly enriched in the leaf epidermis where the pathways for catharanthine and tabersonine biosynthesis are expressed. The full elucidation of this canonical pathway enables synthetic biology approaches for manufacturing a broad range of MIAs, including these dimers used in cancer treatment.
Significance Statement
The identification of O‐acetylstemmadenine oxidase and a dual function geissoschizine synthase completes the 28‐step pathway for assembly of anticancer alkaloids vinblastine and vincristine in Catharanthus roseus. The full elucidation of this canonical pathway enables synthetic biology approaches for manufacturing a broad range of MIAs including these dimers used in cancer treatment.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Catharanthus roseus is the sole commercial source of the monoterpenoid indole alkaloids (MIAs), vindoline and catharanthine, components of the commercially important anticancer dimers, vinblastine ...and vincristine. Carborundum abrasion technique was used to extract leaf epidermis-enriched mRNA, thus sampling the epidermome, or complement, of proteins expressed in the leaf epidermis. Random sequencing of the derived cDNA library established 3655 unique ESTs, composed of 1142 clusters and 2513 singletons. Virtually all known MIA pathway genes were found in this remarkable set of ESTs, while only four known genes were found in the publicly available Catharanthus EST data set. Several novel MIA pathway candidate genes were identified, as demonstrated by the cloning and functional characterization of loganic acid O-methyltransferase involved in secologanin biosynthesis. The pathways for triterpene biosynthesis were also identified, and metabolite analysis showed that oleanane-type triterpenes were localized exclusively to the cuticular wax layer. The pathways for flavonoid and very-long-chain fatty acid biosynthesis were also located in this cell type. The results illuminate the biochemical specialization of Catharanthus leaf epidermis for the production of multiple classes of metabolites. The value and versatility of this EST data set for biochemical and biological analysis of leaf epidermal cells is also discussed.
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•Patients with AD had significantly prolonged P300 latencies compared to unaffected controls.•Differences in P300 latency effect sizes were influenced by sample characteristics and EEG/ERP lab ...methodologies.•MCI patients had prolonged P300 latencies compared to controls, but shortened P300 latencies when compared to AD patients.•Larger P300 effect size was estimated at Pz relative to midline electrodes between the AD and MCI patient analysis.
The present meta-analysis investigated the clinical utility of the auditory P300 latency event-related potential in differentiating patients with Alzheimer’s disease (AD), patients with mild cognitive impairment (MCI), and unaffected controls. Effect size estimates were computed from mean P300 latency measurements at midline electrodes between patients and unaffected controls using the random effects restricted maximum likelihood model. The effects of clinical and ERP/EEG methological variables were assessed in a moderator analysis. P300 latency was found to be significantly prolonged in patients with AD (and MCI) compared to unaffected controls. Shortened P300 latencies were observed when comparing patients with MCI to patients with AD. Clinically relevant differences in P300 latency effect sizes were associated with mean age, interstimulus interval, stimulus difference, target frequency, reference electrode, and sampling rate. The meta-analytic findings provide robust statistical evidence for the use of the auditory P300 latency subcomponent as a biological marker of prodromal AD.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Only a small fraction of the immense diversity of plant metabolism has been explored for the production of new medicines and other products important to human well-being. The availability of ...inexpensive high-throughput sequencing is rapidly expanding the number of species that can be investigated for the speedy discovery of previously unknown enzymes and pathways. Exploitation of these resources is being carried out through interdisciplinary synthetic and chemical biology to engineer pathways in plant and microbial systems for improving the production of existing medicines and to create libraries of biologically active products that can be screened for new drug applications.
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Using a bisection paradigm, we investigated age-related differences in susceptibility to distractor interference. Older and younger participants were asked to bisect a horizontal line flanked by a ...pair of distractors, placed in either left or right hemispace. The results showed that (1) in both groups the distractors interfered with line bisection so that the localization of subjective midpoint was selectively shifted away from their position; (2) the shifting of subjective midpoint was greater in the older than in the younger group when the distractors were placed in the left hemispace. We suggest that the increase of the bisection bias in the older group depends on changes in attentional mechanisms involved in inhibiting irrelevant information.
It is extremely important for the health to understand the regulatory mechanisms of energy expenditure. These regulatory mechanisms play a central role in the pathogenesis of body weight alteration. ...The hypothalamus integrates nutritional information derived from all peripheral organs. This region of the brain controls hormonal secretions and neural pathways of the brainstem. Orexin-A is a hypothalamic neuropeptide involved in the regulation of feeding behavior, sleep-wakefulness rhythm, and neuroendocrine homeostasis. This neuropeptide is involved in the control of the sympathetic activation, blood pressure, metabolic status, and blood glucose level. This minireview focuses on relationship between the sympathetic nervous system and orexin-A in the control of eating behavior and energy expenditure. The "thermoregulatory hypothesis" of food intake is analyzed, underlining the role played by orexin-A in the control of food intake related to body temperature. Furthermore, the paradoxical eating behavior induced orexin-A is illustrated in this minireview.
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