Dataset Information

Daily mapping of Australian Plague Locust abundance.

ABSTRACT: Locust population outbreaks have been a longstanding problem for Australian agriculture. Since its inception in the mid-1970s, The Australian Plague Locust Commission (APLC) is responsible for monitoring, forecasting and controlling populations of several locust pest species across inland eastern Australia (ca. two million km²). Ground surveys are typically targeted according to prevailing environmental conditions. However, due to the sheer size of the region and limited resources, such surveys remain sparse. Here we develop daily time-step statistical models of populations of Chortoicetes terminifera (Australian plague locust) that can used to predict abundances when observations are lacking, plus uncertainties. We firstly identified key environmental covariates of locust abundance, then examined their relationship with C. terminifera populations by interpreting the responses of Generalized Additive Models (GAM). We also illustrate how estimates of C. terminifera abundance plus uncertainties can be visualized across the region. Our results support earlier studies, specifically, populations peak in grasslands with high productivity, and decline rapidly under very hot and dry conditions. We also identified new relationships, specifically, a strong positive effect of vapour pressure and sunlight, and a negative effect of soil sand content on C. terminifera abundance. Our modelling tool may assist future APLC management and surveillance effort.

SUBMITTER: Mangeon S

PROVIDER: S-EPMC7547006 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Daily mapping of Australian Plague Locust abundance.

Mangeon Stéphane S Spessa Allan A Deveson Edward E Darnell Ross R Kriticos Darren J DJ

Scientific reports 20201009 1

Locust population outbreaks have been a longstanding problem for Australian agriculture. Since its inception in the mid-1970s, The Australian Plague Locust Commission (APLC) is responsible for monitoring, forecasting and controlling populations of several locust pest species across inland eastern Australia (ca. two million km<sup>2</sup>). Ground surveys are typically targeted according to prevailing environmental conditions. However, due to the sheer size of the region and limited resources, su ...[more]

PMID: 33037298

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Project description:BACKGROUND: The Australian plague locust, Chortoicetes terminifera, is among the most promising species to unravel the suites of genes underling the density-dependent shift from shy and cryptic solitarious behaviour to the highly active and aggregating gregarious behaviour that is characteristic of locusts. This is because it lacks many of the major phenotypic changes in colour and morphology that accompany phase change in other locust species. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is the most sensitive method available for determining changes in gene expression. However, to accurately monitor the expression of target genes, it is essential to select an appropriate normalization strategy to control for non-specific variation between samples. Here we identify eight potential reference genes and examine their expression stability at different rearing density treatments in neural tissue of the Australian plague locust. RESULTS: Taking advantage of the new orthologous DNA sequences available in locusts, we developed primers for genes encoding 18SrRNA, ribosomal protein L32 (RpL32), armadillo (Arm), actin 5C (Actin), succinate dehydrogenase (SDHa), glyceraldehyde-3P-dehydrogenase (GAPDH), elongation factor 1 alpha (EF1a) and annexin IX (AnnIX). The relative transcription levels of these eight genes were then analyzed in three treatment groups differing in rearing density (isolated, short- and long-term crowded), each made up of five pools of four neural tissue samples from 5th instar nymphs. SDHa and GAPDH, which are both involved in metabolic pathways, were identified as the least stable in expression levels, challenging their usefulness in normalization. Based on calculations performed with the geNorm and NormFinder programs, the best combination of two genes for normalization of gene expression data following crowding in the Australian plague locust was EF1a and Arm. We applied their use to studying a target gene that encodes a Ca2+ binding glycoprotein, SPARC, which was previously found to be up-regulated in brains of gregarious desert locusts, Schistocerca gregaria. Interestingly, expression of this gene did not vary with rearing density in the same way in brains of the two locust species. Unlike S. gregaria, there was no effect of any crowding treatment in the Australian plague locust. CONCLUSION: Arm and EF1a is the most stably expressed combination of two reference genes of the eight examined for reliable normalization of RT-qPCR assays studying density-dependent behavioural change in the Australian plague locust. Such normalization allowed us to show that C. terminifera crowding did not change the neuronal expression of the SPARC gene, a gregarious phase-specific gene identified in brains of the desert locust, S. gregaria. Such comparative results on density-dependent gene regulation provide insights into the evolution of gregarious behaviour and mass migration of locusts. The eight identified genes we evaluated are also candidates as normalization genes for use in experiments involving other Oedipodinae species, but the rank order of gene stability must necessarily be determined on a case-by-case basis.

Project description:Retinal function changes dramatically from day to night. Yet, clinical diagnosis, treatments, and experimental sampling occur during the day, leaving a significant gap in our understanding of the pathobiology occurring at night. While there is evidence that diabetes disrupts the circadian system that optimizes our physiology to the environmental light/dark cycle, the impact of such disruption is not well understood. This study investigates whether diabetes affects the retina's daily rhythm of gene expression to understand the pathobiology of diabetic retinopathy, a common complication of diabetes. Control and hyperglycemic littermate mice (Ins2Akita/J) were kept under a standard 12h:12h light/dark cycle until four months of age. Bulk mRNA sequencing was conducted in retinas collected every 4 hours throughout the 24 hr light/dark cycle. Computational approaches were used to detect rhythmicity, predict acrophase, identify differential rhythmic patterns, analyze phase set enrichment, and predict upstream regulators. The retinal transcriptome exhibited a tightly regulated rhythmic expression with a clear 12-hr axis of transcriptional rush, peaking at midday and midnight. The functions of day-peaking genes were enriched for DNA repair, RNA splicing, and ribosomal protein synthesis, whereas night-peaking genes were enriched for metabolic processes and growth factor signaling. Although the 12-hr transcriptional axis is retained in the diabetic retina, it was phase advanced by approximately 1-3 hours with a wider distribution. Upstream regulator analysis for the genes that showed phase shifts identified oxygen sensing mechanisms and HIF1alpha as regulators, but not the circadian clock, which remained in phase to the light/dark cycle. We propose a model in which early in diabetes, the diabetic retina experiences a ‘jet lag’ caused by the entrained circadian clock and its output being in one phase and metabolic pathways related to neuronal dysfunction and hypoxia driving advancement of gene expression to a different phase. Further studies are now required to evaluate the chronic implications of such internal jet lag for development of diabetic retinopathy.

Dataset Information

Daily mapping of Australian Plague Locust abundance.

Publications

Daily mapping of Australian Plague Locust abundance.

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