Photosystem II oxygen-evolving complex photoassembly displays an inverse H/D solvent isotope effect under chloride-limiting conditions

© 2019 National Academy of Sciences. All rights reserved. Photosystem II (PSII) performs the solar-driven oxidation of water used to fuel oxygenic photosynthesis. The active site of water oxidation is the oxygen-evolving complex (OEC), a Mn4CaO5 cluster. PSII requires degradation of key subunits and reassembly of the OEC as frequently as every 20 to 40 min. The metals for the OEC are assembled within the PSII protein environment via a series of binding events and photochemically induced oxidation events, but the full mechanism is unknown. A role of proton release in this mechanism is suggested here by the observation that the yield of in vitro OEC photoassembly is higher in deuterated water, D2O, compared with H2O when chloride is limiting. In kinetic studies, OEC photoassembly shows a significant lag phase in H2O at limiting chloride concentrations with an apparent H/D solvent isotope effect of 0.14 ± 0.05. The growth phase of OEC photoassembly shows an H/D solvent isotope effect of 1.5 ± 0.2. We analyzed the protonation states of the OEC protein environment using classical Multiconformer Continuum Electrostatics. Combining experiments and simulations leads to a model in which protons are lost from amino acid that will serve as OEC ligands as metals are bound. Chloride and D2O increase the proton affinities of key amino acid residues. These residues tune the binding affinity of Mn2+/3+ and facilitate the deprotonation of water to form a proposed μ-hydroxo bridged Mn2+Mn3+ intermediate

An initial comparative map of copy number variations in the goat (Capra hircus) genome

<p>Abstract</p> <p>Background</p> <p>The goat (<it>Capra hircus</it>) represents one of the most important farm animal species. It is reared in all continents with an estimated world population of about 800 million of animals. Despite its importance, studies on the goat genome are still in their infancy compared to those in other farm animal species. Comparative mapping between cattle and goat showed only a few rearrangements in agreement with the similarity of chromosome banding. We carried out a cross species cattle-goat array comparative genome hybridization (aCGH) experiment in order to identify copy number variations (CNVs) in the goat genome analysing animals of different breeds (Saanen, Camosciata delle Alpi, Girgentana, and Murciano-Granadina) using a tiling oligonucleotide array with ~385,000 probes designed on the bovine genome.</p> <p>Results</p> <p>We identified a total of 161 CNVs (an average of 17.9 CNVs per goat), with the largest number in the Saanen breed and the lowest in the Camosciata delle Alpi goat. By aggregating overlapping CNVs identified in different animals we determined CNV regions (CNVRs): on the whole, we identified 127 CNVRs covering about 11.47 Mb of the virtual goat genome referred to the bovine genome (0.435% of the latter genome). These 127 CNVRs included 86 loss and 41 gain and ranged from about 24 kb to about 1.07 Mb with a mean and median equal to 90,292 bp and 49,530 bp, respectively. To evaluate whether the identified goat CNVRs overlap with those reported in the cattle genome, we compared our results with those obtained in four independent cattle experiments. Overlapping between goat and cattle CNVRs was highly significant (P < 0.0001) suggesting that several chromosome regions might contain recurrent interspecies CNVRs. Genes with environmental functions were over-represented in goat CNVRs as reported in other mammals.</p> <p>Conclusions</p> <p>We describe a first map of goat CNVRs. This provides information on a comparative basis with the cattle genome by identifying putative recurrent interspecies CNVs between these two ruminant species. Several goat CNVs affect genes with important biological functions. Further studies are needed to evaluate the functional relevance of these CNVs and their effects on behavior, production, and disease resistance traits in goats.</p

PREDICT identifies precipitating events associated with the clinical course of acutely decompensated cirrhosis

Background & Aims: Acute decompensation (AD) of cirrhosis may present without acute-on-chronic liver failure (ACLF) (ADNo ACLF), or with ACLF (AD-ACLF), defined by organ failure(s). Herein, we aimed to analyze and characterize the precipitants leading to both of these AD phenotypes. Methods: The multicenter, prospective, observational PREDICT study (NCT03056612) included 1,273 non-electively hospitalized patients with AD (No ACLF = 1,071; ACLF = 202). Medical history, clinical data and laboratory data were collected at enrolment and during 90-day follow-up, with particular attention given to the following characteristics of precipitants: induction of organ dysfunction or failure, systemic inflammation, chronology, intensity, and relationship to outcome. Results: Among various clinical events, 4 distinct events were precipitants consistently related to AD: proven bacterial infections, severe alcoholic hepatitis, gastrointestinal bleeding with shock and toxic encephalopathy. Among patients with precipitants in the AD-No ACLF cohort and the AD-ACLF cohort (38% and 71%, respectively), almost all (96% and 97%, respectively) showed proven bacterial infection and severe alcoholic hepatitis, either alone or in combination with other events. Survival was similar in patients with proven bacterial infections or severe alcoholic hepatitis in both AD phenotypes. The number of precipitants was associated with significantly increased 90day mortality and was paralleled by increasing levels of surrogates for systemic inflammation. Importantly, adequate first-line antibiotic treatment of proven bacterial infections was associated with a lower ACLF development rate and lower 90-day mortality. Conclusions: This study identified precipitants that are significantly associated with a distinct clinical course and prognosis in patients with AD. Specific preventive and therapeutic strategies targeting these events may improve outcomes in patients with decompensated cirrhosis. Lay summary: Acute decompensation (AD) of cirrhosis is characterized by a rapid deterioration in patient health. Herein, we aimed to analyze the precipitating events that cause AD in patients with cirrhosis. Proven bacterial infections and severe alcoholic hepatitis, either alone or in combination, accounted for almost all (96-97%) cases of AD and acute-on-chronic liver failure. Whilst the type of precipitant was not associated with mortality, the number of precipitant(s) was. This study identified precipitants that are significantly associated with a distinct clinical course and prognosis of patients with AD. Specific preventive and therapeutic strategies targeting these events may improve patient outcomes. (c) 2020 European Association for the Study of the Liver. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Variation in susceptibility of rice lines to infestation by the rice water weevil (Coleoptera: Curculionidae)

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is an important insect pest of rice in the United States and Asia. Current management programs for this pest rely heavily on insecticides. Host plant resistance is an underused strategy for management of this pest. In the experiments reported here, the susceptibilities of 19 rice lines to infestation by the rice water weevil were evaluated in greenhouse experiments. The lines screened in this study had exhibited either resistance or susceptibility (relative to commercial varieties) in previous field screening experiments. Thus, the purpose of these experiments was to confirm the presence of resistance/ susceptibility in these lines and to assess variation in susceptibility relative to two commercial varieties. Both choice and no-choice experiments were conducted. The experiments were designed primarily to detect antixenosis. Rice lines screened in these experiments exhibited significant variation in their susceptibilities to infestation by L. oryzophilus. Some of the lines consistently supported fewer weevil eggs and larvae than commercial varieties, whereas others consistently supported more eggs and larvae than commercial varieties. The lines exhibiting resistance (PI 319512, PI 321310, PI 321264, and PI 321278) had also exhibited resistance in at least four prior field experiments, and may be useful as germplasm in a breeding program. The identification of lines possessing both resistance and susceptibility may facilitate the characterization of biochemical or morphological mechanisms of resistance to the rice water weevil in these lines

Variation in Susceptibility of Rice Lines to Infestation by the Rice Water Weevil (Coleoptera: Curculionidae)

ABSTRACT The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is an important insect pest of rice in the United States and Asia. Current management programs for this pest rely heavily on insecticides. Host plant resistance is an underused strategy for management of this pest. In the experiments reported here, the susceptibilities of 19 rice lines to infestation by the rice water weevil were evaluated in greenhouse experiments. The lines screened in this study had exhibited either resistance or susceptibility (relative to commercial varieties) in previous field screening experiments. Thus, the purpose of these experiments was to confirm the presence of resistance/ susceptibility in these lines and to assess variation in susceptibility relative to two commercial varieties. Both choice and no-choice experiments were conducted. The experiments were designed primarily to detect antixenosis. Rice lines screened in these experiments exhibited significant variation in their susceptibilities to infestation by L. oryzophilus. Some of the lines consistently supported fewer weevil eggs and larvae than commercial varieties, whereas others consistently supported more eggs and larvae than commercial varieties. The lines exhibiting resistance (PI 319512, PI 321310, PI 321264, and PI 321278) had also exhibited resistance in at least four prior field experiments, and may be useful as germplasm in a breeding program. The identification of lines possessing both resistance and susceptibility may facilitate the characterization of biochemical or morphological mechanisms of resistance to the rice water weevil in these lines

Herbivore- and Elicitor-Induced Resistance in Rice to the Rice Water Weevil (Lissorhoptrus oryzophilus Kuschel) in the Laboratory and Field

Feeding by herbivores can change plants in ways that make them more resistant to subsequent herbivory. Such induced responses are better-studied in a number of model dicots than in rice and other cereals. In a series of greenhouse and field experiments, we assessed the effects of prior herbivory by the fall armyworm, Spodoptera frugiperda (J. E. Smith) and of exogenous applications of jasmonic acid (JA) on the resistance of rice plants to the rice water weevil, Lissorhoptrus oryzophilus (Kuschel), the major pest of rice in the United States. Prior feeding by S. frugiperda and treatment of plants with exogenous JA resulted in increases in the resistance of plants to the weevil. Increases in resistance were manifested as reduced numbers of eggs and first-instars associated with armyworm-injured or JA-treated plants relative to control plants. In field experiments, there was a transient but significant reduction in the number of immature L. oryzophilus on JA-treated plants relative to untreated plants. To our knowledge, this is the first example of direct induced resistance in rice demonstrated in small-plot field experiments. We discuss the potential for the use of elicitor induced resistance in rice. © 2010 Springer Science+Business Media, LLC

Flooding influences ovipositional and feeding behavior of the rice water weevil (Coleoptera: Curculionidae).

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the United States. As part of an effort to develop strategies to manage this pest, the ovipositional and feeding habits of L. oryzophilus on rice plants subjected to different flooding treatments were characterized in greenhouse studies. Presence and depth of flood had a direct influence on the ovipositional behavior of weevils in no-choice studies. More eggs were found in flooded plants than in unflooded plants. Moreover, plants flooded to a depth of 5.1 cm received more eggs than plants flooded to depths of 1.3 or 10.2 cm. Presence and depth of flood influenced both the proportion of females that oviposited in plants and the number of eggs laid by those females that did oviposit. In choice studies, female weevils showed a marked ovipositional preference for plants flooded to a depth of 10.2 cm over unflooded plants and plants flooded to a depth of 1.3 cm. In separate choice experiments, adult rice water weevils fed more on flooded plants than on unflooded plants. In a third set of experiments, flooded plants were taller and had higher concentrations of 10 of 13 plant nutrients than unflooded plants. Thus, flooding may influence rice water weevil behavior both directly, by acting as a stimulus for feeding or oviposition, and indirectly, by inducing changes in the suitability of rice plants for feeding or oviposition. These data suggest that it may be possible to manipulate populations of weevils in rice by changing water management practices

Jasmonic acid-induced resistance to the fall armyworm, Spodoptera frugiperda, in conventional and transgenic cottons expressing Bacillus thuringiensis insecticidal proteins

To assess potential interactions between Bacillus thuringiensis Berliner (Bt) proteins and jasmonic acid (JA)-induced resistance to the fall armyworm, Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae), three commercial Stoneville cotton cultivars, Gossypium hirsutum L. (Malvaceae) (\u27ST 475\u27, a conventional cultivar; \u27ST 4575 BR\u27, a Bollgard ® cultivar expressing Cry1Ac protein; and \u27ST 4554B2RF\u27, a Bollgard II ® cultivar expressing Cry2Ab2 in addition to Cry1Ac), were treated with JA. Two experiments were conducted with 6-day-old S. frugiperda larvae on three cotton cultivars at two phenological stages. The first experiment was conducted under laboratory conditions and used excised cotton leaves; the second experiment was performed under greenhouse conditions on intact cotton plants. Relative growth rates (RGRs) and leaf area consumed by 6-day-old S. frugiperda larvae were determined for each combination of treatments. Overall, JA treatment and cultivars significantly impacted RGR and leaf area consumption. Significant JA treatment *cultivar interactions were observed for RGR of larvae in the laboratory experiment and for leaf area consumption in the greenhouse experiment. An additional experiment evaluated S. frugiperda neonates on the same JA and cotton cultivar combinations (at a single phenological stage) under laboratory conditions. Neonate survival was determined after 3, 5, and 10days of feeding, and final larval weight after 10days of feeding. Overall, JA treatment and cultivars significantly impacted final weight and survival of S. frugiperda. Significant JA treatment *cultivar interactions were observed for final weight and on overall survival of S. frugiperda. Combination of the cotton tissue expressing pyramided Bt proteins with JA treatment demonstrated the greatest negative impact on larval development. Apparent synergism between Bt proteins and JA-induced resistance emphasizes that traditional host plant resistance has a role to play in combination with Bt technology. © 2011 The Authors. Entomologia Experimentalis et Applicata © 2011 The Netherlands Entomological Society