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Author

David A. Schooley

Other affiliations: University of Toronto
Bio: David A. Schooley is an academic researcher from University of Nevada, Reno. The author has contributed to research in topics: Juvenile hormone & Manduca sexta. The author has an hindex of 48, co-authored 137 publications receiving 7899 citations. Previous affiliations of David A. Schooley include University of Toronto.


Papers
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Journal ArticleDOI
TL;DR: Different differences between water deficit and salinity were revealed and water-deficit-treated plants appear to have a higher demand than salinized plants to adjust osmotically, detoxify free radicals (reactive oxygen species), and cope with photoinhibition.
Abstract: Grapes are grown in semiarid environments, where drought and salinity are common problems. Microarray transcript profiling, quantitative reverse transcription-PCR, and metabolite profiling were used to define genes and metabolic pathways in Vitis vinifera cv. Cabernet Sauvignon with shared and divergent responses to a gradually applied and long-term (16 days) water-deficit stress and equivalent salinity stress. In this first-of-a-kind study, distinct differences between water deficit and salinity were revealed. Water deficit caused more rapid and greater inhibition of shoot growth than did salinity at equivalent stem water potentials. One of the earliest responses to water deficit was an increase in the transcript abundance of RuBisCo activase (day 4), but this increase occurred much later in salt-stressed plants (day 12). As water deficit progressed, a greater number of affected transcripts were involved in metabolism, transport, and the biogenesis of cellular components than did salinity. Salinity affected a higher percentage of transcripts involved in transcription, protein synthesis, and protein fate than did water deficit. Metabolite profiling revealed that there were higher concentrations of glucose, malate, and proline in water-deficit-treated plants as compared to salinized plants. The metabolite differences were linked to differences in transcript abundance of many genes involved in energy metabolism and nitrogen assimilation, particularly photosynthesis, gluconeogenesis, and photorespiration. Water-deficit-treated plants appear to have a higher demand than salinized plants to adjust osmotically, detoxify free radicals (reactive oxygen species), and cope with photoinhibition.

541 citations

Journal ArticleDOI
TL;DR: The first high-resolution picture of the transcriptome dynamics that occur during seven stages of grape berry development is revealed and a set of previously unknown genes potentially involved in critical steps associated with fruit development can now be subjected to functional testing.
Abstract: Grape berry development is a dynamic process that involves a complex series of molecular genetic and biochemical changes divided into three major phases. During initial berry growth (Phase I), berry size increases along a sigmoidal growth curve due to cell division and subsequent cell expansion, and organic acids (mainly malate and tartrate), tannins, and hydroxycinnamates accumulate to peak levels. The second major phase (Phase II) is defined as a lag phase in which cell expansion ceases and sugars begin to accumulate. Veraison (the onset of ripening) marks the beginning of the third major phase (Phase III) in which berries undergo a second period of sigmoidal growth due to additional mesocarp cell expansion, accumulation of anthocyanin pigments for berry color, accumulation of volatile compounds for aroma, softening, peak accumulation of sugars (mainly glucose and fructose), and a decline in organic acid accumulation. In order to understand the transcriptional network responsible for controlling berry development, mRNA expression profiling was conducted on berries of V. vinifera Cabernet Sauvignon using the Affymetrix GeneChip® Vitis oligonucleotide microarray ver. 1.0 spanning seven stages of berry development from small pea size berries (E-L stages 31 to 33 as defined by the modified E-L system), through veraison (E-L stages 34 and 35), to mature berries (E-L stages 36 and 38). Selected metabolites were profiled in parallel with mRNA expression profiling to understand the effect of transcriptional regulatory processes on specific metabolite production that ultimately influence the organoleptic properties of wine. Over the course of berry development whole fruit tissues were found to express an average of 74.5% of probes represented on the Vitis microarray, which has 14,470 Unigenes. Approximately 60% of the expressed transcripts were differentially expressed between at least two out of the seven stages of berry development (28% of transcripts, 4,151 Unigenes, had pronounced (≥2 fold) differences in mRNA expression) illustrating the dynamic nature of the developmental process. The subset of 4,151 Unigenes was split into twenty well-correlated expression profiles. Expression profile patterns included those with declining or increasing mRNA expression over the course of berry development as well as transient peak or trough patterns across various developmental stages as defined by the modified E-L system. These detailed surveys revealed the expression patterns for genes that play key functional roles in phytohormone biosynthesis and response, calcium sequestration, transport and signaling, cell wall metabolism mediating expansion, ripening, and softening, flavonoid metabolism and transport, organic and amino acid metabolism, hexose sugar and triose phosphate metabolism and transport, starch metabolism, photosynthesis, circadian cycles and pathogen resistance. In particular, mRNA expression patterns of transcription factors, abscisic acid (ABA) biosynthesis, and calcium signaling genes identified candidate factors likely to participate in the progression of key developmental events such as veraison and potential candidate genes associated with such processes as auxin partitioning within berry cells, aroma compound production, and pathway regulation and sequestration of flavonoid compounds. Finally, analysis of sugar metabolism gene expression patterns indicated the existence of an alternative pathway for glucose and triose phosphate production that is invoked from veraison to mature berries. These results reveal the first high-resolution picture of the transcriptome dynamics that occur during seven stages of grape berry development. This work also establishes an extensive catalog of gene expression patterns for future investigations aimed at the dissection of the transcriptional regulatory hierarchies that govern berry development in a widely grown cultivar of wine grape. More importantly, this analysis identified a set of previously unknown genes potentially involved in critical steps associated with fruit development that can now be subjected to functional testing.

401 citations

Journal ArticleDOI
17 Mar 1989-Science
TL;DR: A peptide that strongly stimulates the secretion of juvenile hormone from corpora allata in vitro (allatotropin) has been purified from extracts of heads of pharate adult Manduca sexta and has no sequence similarity with any known neuropeptide from other organisms.
Abstract: A peptide that strongly stimulates the secretion of juvenile hormone from corpora allata in vitro (allatotropin) has been purified from extracts of heads of pharate adult Manduca sexta. The primary structure of this 13-residue peptide has been determined: H-Gly-Phe-Lys-Asn-Val-Glu-Met-Met-Thr-Ala-Arg-Gly-Phe-NH2. This neurohormone has no sequence similarity with any known neuropeptide from other organisms. Synthetic allatotropin, as well as truncation fragments, including one with the five amino terminal residues deleted, showed in vitro activity indistinguishable from that of native allatotropin.

334 citations

Journal ArticleDOI
09 Jan 1987-Science
TL;DR: Results indicate that JH-like compounds such as methyl farnesoate have regulatory roles in crustaceans.
Abstract: Juvenile hormone (JH) has central roles in the regulation of insect development and reproduction but has not previously been identified in other arthropod classes. The hemolymph of a crustacean, Libinia emarginata (Leach), has now been analyzed for JH-like compounds. Samples contained 0.003 to 0.030 nanogram of JH III per milliliter and 10 to 50 nanograms of methyl farnesoate per milliliter; methyl farnesoate is a compound structurally related to JH III that has JH bioactivity. Several tissues were examined for synthesis and secretion of JH-like compounds. Of these tissues, only the mandibular organs produced and secreted JH III and methyl farnesoate. However, microchemical analysis revealed that this JH III was racemic, and thus likely an artifactual oxidation product of methyl farnesoate. Secretion of methyl farnesoate was related to reproduction in females, with the highest rates observed in Libinia near the end of the ovarian cycle when oocyte growth and vitellogenesis are greatest. These results indicate that JH-like compounds such as methyl farnesoate have regulatory roles in crustaceans.

298 citations

Journal ArticleDOI
TL;DR: A peptide that strongly inhibits juvenile hormone biosynthesis in vitro by the corpora allata from fifth-stadium larvae and adult females has been purified from extracts of heads of pharate adult M. sexta by a nine-step purification procedure and has no sequence similarity with any known neuropeptide from other organisms.
Abstract: A peptide (Manduca sexta allatostatin) that strongly inhibits juvenile hormone biosynthesis in vitro by the corpora allata from fifth-stadium larvae and adult females has been purified from extracts of heads of pharate adult M. sexta by a nine-step purification procedure. The primary structure of this 15-residue peptide has been determined: pGlu-Val-Arg-Phe-Arg-Gln-Cys- Tyr-Phe-Asn-Pro-Ile-Ser-Cys-Phe-OH, where pGlu is pyroglutamate). To our knowledge, this neuro-hormone has no sequence similarity with any known neuropeptide from other organisms. The synthetic free acid and amide forms showed in vitro activity indistinguishable from that of native M. sexta allatostatin. The ED50 of synthetic M. sexta allatostatin on early fifth stadium larval corpora allata in vitro was approximately 2 nM. This inhibition was reversible. In a cross-species study, M. sexta allatostatin also inhibited the corpora allata of adult female Heliothis virescens but had no effect on the activity of corpora allata of adult females of the beetle Tenebrio molitor, the grasshopper Melanoplus sanguinipes, or the cockroach Periplaneta americana.

275 citations


Cited by
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Journal ArticleDOI
TL;DR: It is becoming apparent that plants perceive and respond to drought and salt stresses by quickly altering gene expression in parallel with physiological and biochemical alterations; this occurs even under mild to moderate stress conditions.

3,080 citations

MonographDOI
12 Nov 1998
TL;DR: The aim of this monograph is to clarify the role of pheromones and chemicals in the lives of Insects and to propose a strategy to address their role in the food web.
Abstract: The Insects has been the standard textbook in the field since the first edition published over forty years ago. Building on the strengths of Chapman's original text, this long-awaited 5th edition has been revised and expanded by a team of eminent insect physiologists, bringing it fully up-to-date for the molecular era. The chapters retain the successful structure of the earlier editions, focusing on particular functional systems rather than taxonomic groups and making it easy for students to delve into topics without extensive knowledge of taxonomy. The focus is on form and function, bringing together basic anatomy and physiology and examining how these relate to behaviour. This, combined with nearly 600 clear illustrations, provides a comprehensive understanding of how insects work. Now also featuring a richly illustrated prologue by George McGavin, this is an essential text for students, researchers and applied entomologists alike.

2,922 citations

Journal ArticleDOI
TL;DR: Information about metabolic regulation in response to drought, extreme temperature, and salinity stress is summarized and the signalling events involved in mediating stress-induced metabolic changes are presented.
Abstract: Plants regularly face adverse growth conditions, such as drought, salinity, chilling, freezing, and high temperatures. These stresses can delay growth and development, reduce productivity, and, in extreme cases, cause plant death. Plant stress responses are dynamic and involve complex cross-talk between different regulatory levels, including adjustment of metabolism and gene expression for physiological and morphological adaptation. In this review, information about metabolic regulation in response to drought, extreme temperature, and salinity stress is summarized and the signalling events involved in mediating stress-induced metabolic changes are presented.

1,683 citations

Journal ArticleDOI
TL;DR: In this review, research progress in plant responses to abiotic stresses is summarized from the physiological level to the molecular level, providing additional focus areas for crop improvement research in the future.
Abstract: The natural environment for plants is composed of a complex set of abiotic stresses and biotic stresses. Plant responses to these stresses are equally complex. Systems biology approaches facilitate a multi-targeted approach by allowing one to identify regulatory hubs in complex networks. Systems biology takes the molecular parts (transcripts, proteins and metabolites) of an organism and attempts to fit them into functional networks or models designed to describe and predict the dynamic activities of that organism in different environments. In this review, research progress in plant responses to abiotic stresses is summarized from the physiological level to the molecular level. New insights obtained from the integration of omics datasets are highlighted. Gaps in our knowledge are identified, providing additional focus areas for crop improvement research in the future.

1,056 citations

Journal ArticleDOI
TL;DR: This review of recent advances in understanding chitin synthesis and its degradation in insects will summarize recent advances.
Abstract: Chitin is one of the most important biopolymers in nature. It is mainly produced by fungi, arthropods and nematodes. In insects, it functions as scaffold material, supporting the cuticles of the epidermis and trachea as well as the peritrophic matrices lining the gut epithelium. Insect growth and morphogenesis are strictly dependent on the capability to remodel chitin-containing structures. For this purpose, insects repeatedly produce chitin synthases and chitinolytic enzymes in different tissues. Coordination of chitin synthesis and its degradation requires strict control of the participating enzymes during development. In this review, we will summarize recent advances in understanding chitin synthesis and its degradation in insects.

1,037 citations