Publications by authors named "Shawn M Clark"

Leaf beetles (Coleoptera: Chrysomelidae) constitute a family of abundant, diverse, and ecologically important herbivorous insects, due to their high specificity with host plants, a close association with vegetation and a great sensitivity to microclimatic variation (factors that are modified gradually during the rainy and dry seasons). Therefore, the effects of seasonality (rainy and dry seasons) and microclimate on the community attributes of chrysomelids were evaluated in a semideciduous tropical forest fragment of northeastern Mexico. Monthly sampling was conducted, between March 2016 and February 2017, with an entomological sweep net in 18 plots of 20 × 20 m, randomly distributed from 320 to 480 m a.

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Viswajyothi & Clark, , is described and illustrated. The genus is placed in the chrysomelid section Diabroticites Chapuis (subtribe Diabroticina Chapuis, tribe Luperini Chapuis, subfamily Galerucinae Latreille). It is monobasic, containing Viswajyothi & Clark, , from Ecuador.

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Leaf beetles (Chrysomelidae: Coleoptera) constitute a highly diverse family of phytophagous insects with high ecological relevance, due to their host plant specificity and their close association to vegetation variables. Therefore, secondary succession and seasonal changes after loss of vegetal cover will have a significant influence on their community patterns. Accordingly, responses of leaf beetles to such environmental heterogeneity make them a suitable taxon for monitoring disturbance, which is more important for endangered habitats such as the low thorn forests (LTF) in northeastern Mexico.

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Background: We provide volume II of a distributional atlas of aquatic insects for the eastern USA state of Ohio. This treatment of stoneflies (Plecoptera) is companion to Armitage et al. (2011) on caddisflies (Trichoptera).

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Abscisic acid (ABA) is a well-characterized plant hormone, known to mediate developmental aspects as well as both abiotic and biotic stress responses. Notably, the exogenous application of ABA has recently been shown to increase susceptibility to the fungal pathogen Fusarium graminearum, the causative agent of Fusarium head blight (FHB) in wheat and other cereals. However roles and mechanisms associated with ABA's modulation of pathogen responses remain enigmatic.

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The study of biodiversity of Chrysomelidae in Mexico and its variation within ecological gradients has increased recently, although important areas in the country remain to be explored. We conducted a faunistic inventory and analyzed the elevational and temporal variation of leaf beetle communities in the Sierra de San Carlos, in the state of Tamaulipas, in northeastern Mexico. This is an area with high to extreme priority for conservation, and due to its insular geographical position and to the vegetational communities present, it must be considered as a sky island.

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We record 116 genera and 366 species of Chrysomelidae from the state of Morelos, Mexico. This represents an increase of 9.3% in the species richness of these beetles for the state.

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Background: Virus-induced gene silencing (VIGS) has become an emerging technology for the rapid, efficient functional genomic screening of monocot and dicot species. The barley stripe mosaic virus (BSMV) has been described as an effective VIGS vehicle for the evaluation of genes involved in wheat and barley phytopathogenesis; however, these studies have been obscured by BSMV-induced phenotypes and defense responses. The utility of BSMV VIGS may be improved using a BSMV genetic background which is more tolerable to the host plant especially upon secondary infection of highly aggressive, necrotrophic pathogens such as Fusarium graminearum.

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Article Synopsis
  • The West Indian genus Monotalla Bechyné has been reviewed and redescribed, with illustrations included.
  • Five new species of Monotalla have been identified: from Dominica, St. Lucia, and Grenada.
  • A key for identifying different Monotalla species is provided for reference.
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Acyl coenzyme A (acyl-CoA) thioesters are important intermediates in cellular metabolism and being able to distinguish among them is critical to fully understanding metabolic pathways in plants. Although significant advances have been made in the identification and quantification of acyl-CoAs using liquid chromatography tandem mass spectrometry (LC-MS/MS), separation of isomeric species such as isobutyryl- and n-butyrl-CoA has remained elusive. Here we report an ultra-performance liquid chromatography (UPLC)-MS/MS method for quantifying short-chain acyl-CoAs including isomeric species n-butyryl-CoA and isobutyryl-CoA as well as n-valeryl-CoA and isovaleryl-CoA.

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Monoxia obesula Blake, 1939, a species native to North America, is newly found in Sardinia, Italy. This discovery constitutes the first report of the species from Europe, as well as the first report from outside of the U.S.

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Background: The ubiquitous, non-proteinaceous amino acid GABA (γ-aminobutyrate) accumulates in plants subjected to abiotic stresses such as chilling, O2 deficiency and elevated CO2. Recent evidence indicates that controlled atmosphere storage causes the accumulation of GABA in apple (Malus x domestica Borkh.) fruit, and now there is increasing interest in the biochemical mechanisms responsible for this phenomenon.

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Background: Bitter acids (e.g. humulone) are prenylated polyketides synthesized in lupulin glands of the hop plant (Humulus lupulus) which are important contributors to the bitter flavour and stability of beer.

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Δ(9)-Tetrahydrocannabinol (THC) and other cannabinoids are responsible for the psychoactive and medicinal properties of Cannabis sativa L. (marijuana). The first intermediate in the cannabinoid biosynthetic pathway is proposed to be olivetolic acid (OA), an alkylresorcinolic acid that forms the polyketide nucleus of the cannabinoids.

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Article Synopsis
  • A group of plant proteins known as beta-hydroxyacid dehydrogenases includes enzymes that convert succinic semialdehyde to gamma-hydroxybutyrate and glyoxylate to glycolate.
  • Recent studies identify two isoforms of these enzymes (GLYR1 and GLYR2) in Arabidopsis that rely on NADPH for their functions.
  • The review suggests that these enzymes help detoxify aldehydes during stress and maintain redox balance, while also addressing outstanding questions about how this detoxification mechanism is organized within plant cells.
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Gamma-aminobutyric acid transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, three GABA-T isoforms were identified in the tomato (Solanum lycopersicum L.) plant.

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Gamma-aminobutyrate transaminase (GABA-T) catalyses the breakdown of GABA to succinic semialdehyde. In this report, the previously identified Arabidopsis thaliana (L.) Heyhn GABA-T (AtGABA-T) was characterized in more detail.

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Enzymes that reduce the aldehyde chemical grouping (i.e. H-C=O) to its corresponding alcohol are probably crucial in maintaining plant health during stress.

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Article Synopsis
  • Enzymes that convert aldehydes to alcohols play a key role in plant health, and a study identified two variants, AtGR1 and AtGR2, that effectively catalyze this process.
  • Recombinant research demonstrated that AtGR2 preferentially converts glyoxylate to glycolate and succinic semialdehyde to gamma-hydroxybutyrate, with a much higher efficiency for glyoxylate.
  • The localization of these enzymes differs, with AtGR1 found in the cytosol and AtGR2 in plastids, which may impact their roles in detoxifying aldehydes and the plant's response to stress.
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