University of Nevada, Reno

About: University of Nevada, Reno is a education organization based out in Reno, Nevada, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 13561 authors who have published 28217 publications receiving 882002 citations. The organization is also known as: University of Nevada & Nevada State University.

Understanding ecosystem retrogression

Abstract: Over time scales of thousands to millions of years, and in the absence of rejuvenating disturbances that initiate primary or early secondary succession, ecosystem properties such as net primary productivity, decomposition, and rates of nutrient cycling undergo substantial declines termed ecosystem retrogression. Retrogression results from the depletion or reduction in the availability of nutrients, and can only be reversed through rejuvenating disturbance that resets the system; this differs from age-related declines in forest productivity that are driven by shorter-term depression of nutrient availability and plant ecophysiological process rates that occur during succession. Here we review and synthesize the findings from studies of long-term chronosequences that include retrogressive stages for systems spanning the boreal, temperate, and subtropical zones. Ecosystem retrogression has been described by ecologists, biogeochemists, geologists, and pedologists, each of which has developed somewhat independent conceptual frameworks; our review seeks to unify this literature in order to better understand the causes and consequences of retrogression. Studies of retrogression have improved our knowledge of how long-term pedogenic changes drive shorter-term biological processes, as well as the consequences of these changes for ecosystem development. Our synthesis also reveals that similar patterns of retrogression (involving reduced soil fertility, predictable shifts in organismic traits, and ecological processes) occur in systems with vastly different climatic regimes, geologic substrates, and vegetation types, even though the timescales and mechanisms driving retrogression may vary greatly among sites. Studies on retrogression also provide evidence that in many regions, high biomass or "climax" forests are often transient, and do not persist indefinitely in the absence of rejuvenating disturbance. Finally, our review highlights that studies on retrogressive chronosequences in contrasting regions provide unparalleled opportunities for developing general principles about the long-term feedbacks between biological communities and pedogenic processes, and how these control ecosystem development.

A Rice WRKY Gene Encodes a Transcriptional Repressor of the Gibberellin Signaling Pathway in Aleurone Cells

Abstract: The molecular mechanism by which GA regulates plant growth and development has been a subject of active research. Analyses of the rice (Oryza sativa) genomic sequences identified 77 WRKY genes, among which OsWRKY71 is highly expressed in aleurone cells. Transient expression of OsWRKY71 by particle bombardment specifically represses GA-induced Amy32b α-amylase promoter but not abscisic acid-induced HVA22 or HVA1 promoter activity in aleurone cells. Moreover, OsWRKY71 blocks the activation of the Amy32b promoter by the GA-inducible transcriptional activator OsGAMYB. Consistent with its role as a transcriptional repressor, OsWRKY71 is localized to nuclei of aleurone cells and binds specifically to functionally defined TGAC-containing W boxes of the Amy32b promoter in vitro. Mutation of the two W boxes prevents the binding of OsWRKY71 to the mutated promoter, and releases the suppression of the OsGAMYB-activated Amy32b expression by OsWRKY71, suggesting that OsWRKY71 blocks GA signaling by functionally interfering with OsGAMYB. Exogenous GA treatment decreases the steady-state mRNA level of OsWRKY71 and destabilizes the GFP:OsWRKY71 fusion protein. These findings suggest that OsWRKY71 encodes a transcriptional repressor of GA signaling in aleurone cells.

Rapid ecological and behavioural changes in carnivores: the responses of black bears (Ursus americanus) to altered food

Abstract: Many areas have experienced disproportionate increases in the number of conflicts between large carnivores and humans, and this is especially true in western North America where urban sprawl has encroached into regions that have historically contained large carnivores. Yet, globally there is a paucity of studies of temporal changes in behavioural and ecological parameters of carnivores associated with human-induced perturbations at the same location. We capitalized on the extent to which human population growth and its coincident food stores offer a quasi-experimental setting to test hypotheses about the impact of novel food resources. Using black bears Ursus americanus and garbage, measures of behaviour and ecology were contrasted between individuals living in urban– wildland interface (‘experimental’) and in wildland (‘control’) settings at the interface of the Sierra Nevada Range and the Great Basin Desert in the western United States. A temporal dimension was included by comparing our data to those from the same population lacking areas of human encroachment 10–15 years earlier. Specifically, an examination was made of the impacts of garbage on bear time budgets, patterns of activity, and den chronology. Individuals at urban interface areas relative to wildland conspecifics were: (1) active for significantly fewer h per day (8.5 vs 13.3 h; P < 0.01); (2) shifted their activities to nocturnal periods (P < 0.001); (3) entered dens significantly later and remained in them for significantly fewer days (P < 0.05). Our results are contrasted with selected carnivores from sites where attendant changes in behaviour and ecology have accompanied landscape changes associated with human activity. Our findings suggest alterations in carnivore ecology may be rapid and occur within shorter periods than had been previously assumed.

Chemistry, biochemistry, and physiology of insect cuticular lipids

Abstract: The chemistry, biochemistry, and physiology of insect cuticular lipids are reviewed. The types of components present in cuticular extracts are described with special emphasis on the occurrence and identification of the di- and trimethylalkanes and the newly discovered tetramethylalkanes. The methods used in the extraction of cuticular components are discussed, including recommendations to standardize procedures. The structural elucidation of methylalkanes, particularly the mass spectral interpretation of multi-methyl-branched alkanes, is reviewed. The biosynthesis of cuticular lipids is discussed with emphasis on the hydrocarbon components, describing elongation reactions and the origin of the methyl branches. The effects of environment and development on cuticular lipids are reviewed.

ALKBH5-dependent m6A demethylation controls splicing and stability of long 3′-UTR mRNAs in male germ cells

Abstract: N6-methyladenosine (m6A) represents one of the most common RNA modifications in eukaryotes. Specific m6A writer, eraser, and reader proteins have been identified. As an m6A eraser, ALKBH5 specifically removes m6A from target mRNAs and inactivation of Alkbh5 leads to male infertility in mice. However, the underlying molecular mechanism remains unknown. Here, we report that ALKBH5-mediated m6A erasure in the nuclei of spermatocytes and round spermatids is essential for correct splicing and the production of longer 3′-UTR mRNAs, and failure to do so leads to aberrant splicing and production of shorter transcripts with elevated levels of m6A that are rapidly degraded. Our study identified reversible m6A modification as a critical mechanism of posttranscriptional control of mRNA fate in late meiotic and haploid spermatogenic cells.