The cabbage aphid: a walking mustard oil bomb Kazana, Eleanna; Pope, Tom W; Tibbles, Laurienne ...
Proceedings of the Royal Society. B, Biological sciences,
09/2007, Letnik:
274, Številka:
1623
Journal Article
Recenzirano
Odprti dostop
The cabbage aphid, Brevicoryne brassicae, has developed a chemical defence system that exploits and mimics that of its host plants, involving sequestration of the major plant secondary metabolites ...(glucosinolates). Like its host plants, the aphid produces a myrosinase (β-thioglucoside glucohydrolase) to catalyse the hydrolysis of glucosinolates, yielding biologically active products. Here, we demonstrate that aphid myrosinase expression in head/thoracic muscle starts during embryonic development and protein levels continue to accumulate after the nymphs are born. However, aphids are entirely dependent on the host plant for the glucosinolate substrate, which they store in the haemolymph. Uptake of a glucosinolate (sinigrin) was investigated when aphids fed on plants or an in vitro system and followed a different developmental pattern in winged and wingless aphid morphs. In nymphs of the wingless aphid morph, glucosinolate level continued to increase throughout the development to the adult stage, but the quantity in nymphs of the winged form peaked before eclosion (at day 7) and subsequently declined. Winged aphids excreted significantly higher amounts of glucosinolate in the honeydew when compared with wingless aphids, suggesting regulated transport across the gut. The higher level of sinigrin in wingless aphids had a significant negative impact on survival of a ladybird predator. Larvae of Adalia bipunctata were unable to survive when fed adult wingless aphids from a 1% sinigrin diet, but survived successfully when fed aphids from a glucosinolate-free diet (wingless or winged), or winged aphids from 1% sinigrin. The apparent lack of an effective chemical defence system in adult winged aphids possibly reflects their energetic investment in flight as an alternative predator avoidance mechanism.
and Krüger, Kerstin; Van der Waals, Jacquie E
South African journal of science,
11/2020, Letnik:
116, Številka:
11-12
Journal Article
Recenzirano
Odprti dostop
Potato has increased in impor tance as a staple food in sub-Saharan Africa, where its production is faced with a multitude of challenges, including plant disease development and spread under changing ...climatic conditions. The economically most impor tant plant viruses affecting potatoes globally are Potato virus Y (PVY) and Potato leafroll virus (PLRV). Disease management relies mostly on the use of insecticides, cultural control and seed cer tification schemes. A major obstacle in many sub-Saharan Africa countries is the availability of disease-free quality seed potatoes. Establishment and implementation of quality control through specialised seed production systems and cer tification schemes is critical to improve seed potato quality and reduce PVY and PLRV sources. Seed could be fur ther improved by breeding virus-resistant varieties adapted to different environmental conditions combined with management measures tailored for smallholder or commercial farmers to specific agricultural requirements. Innovative technologies including more sensitive testing, remote sensing, machine learning and predictive models - provide new tools for the management of PVY and PLRV, but require suppor t for adoption and implementation in subSaharan Africa.
The growth and ornamental value of chrysanthemums are frequently hindered by aphid attacks. The ethylene-responsive factor (ERF) gene family is pivotal in responding to biotic stress, including ...insect stress. However, to date, little is known regarding the involvement of ERF transcription factors (TFs) in the response of chrysanthemum to aphids.
In the present study, CmHRE2-like from chrysanthemum (Chrysanthemum morifolium), a transcription activator that localizes mainly to the nucleus, was cloned. Expression is induced by aphid infestation. Overexpression of CmHRE2-like in chrysanthemum mediated its susceptibility to aphids, whereas CmHRE2-like-SRDX dominant repressor transgenic plants enhanced the resistance of chrysanthemum to aphids, suggesting that CmHRE2-like contributes to the susceptibility of chrysanthemum to aphids. The flavonoids in CmHRE2-like-overexpression plants were decreased by 29% and 28% in two different lines, whereas they were increased by 42% and 29% in CmHRE2-like-SRDX dominant repressor transgenic plants. The expression of Chrysanthemum-chalcone-synthase gene(CmCHS), chalcone isomerase gene (CmCHI), and flavonoid 3'-hydroxylase gene(CmF3'H) was downregulated in CmHRE2-like overexpression plants and upregulated in CmHRE2-like-SRDX dominant repressor transgenic plants, suggesting that CmHRE2-like regulates the resistance of chrysanthemum to aphids partially through the regulation of flavonoid biosynthesis.
CmHRE2-like was a key gene regulating the vulnerability of chrysanthemum to aphids. This study offers fresh perspectives on the molecular mechanisms of chrysanthemum-aphid interactions and may bear practical significance for developing new strategies to manage aphid infestation in chrysanthemums.
Insect cuticular hydrocarbons (CHCs) play critical roles in reducing water loss and chemical communication. Species-specific CHC profiles have been used increasingly as an excellent character for ...species classification. However, considerably less is known about their potential for population delimitation within species. The aims of this study were to develop a solid-phase microextraction (SPME)-based CHC collection method and to investigate whether CHC profiles could serve as potential chemotaxonomic tools for intraspecific delimitation in Acyrthosiphon pisum. Optimization of fibers for SPME sampling revealed that 7 μm polydimethylsiloxane (PDMS) demonstrated the most efficient adsorption of CHCs among five different tested fibers. SPME sampling showed good reproducibility with repeated collections of CHCs from a single aphid. Validation of SPME was performed by comparing CHC profiles with those from conventional hexane extractions. The two methods showed no qualitative differences in CHCs, although SPME appeared to extract relatively fewer short-chained CHCs. While CHC profiles of a given population differed among developmental stages, wing dimorphism types, and host plants, wingless adult aphids showed very low variance in relative proportions of individual CHC components. Reproducibility of CHC profiles was explored further to classify wingless adult morphs of A. pisum from five different geographic regions that showed no variation in mitochondrial COI gene sequences. Our results demonstrate that CHC profiles are useful in intraspecific delimitation in the field of insect chemotaxonomy.
Mass spectrometry imaging (MSI) is an emerging technology for high-resolution plant biology. It has been utilized to study plant-pest interactions, but limited to the surface interfaces. Here we ...expand the technology to explore the chemical interactions occurring inside the plant tissues. Two sample preparation methods, imprinting and fracturing, were developed and applied, for the first time, to visualize internal metabolites of leaves in matrix-assisted laser desorption ionization (MALDI)-MSI. This is also the first time nanoparticle-based ionization was implemented to ionize diterpenoid phytochemicals that were difficult to analyze with traditional organic matrices. The interactions between rice-bacterium and soybean-aphid were investigated as two model systems to demonstrate the capability of high-resolution MSI based on MALDI. Localized molecular information on various plant- or pest-derived chemicals provided valuable insight for the molecular processes occurring during the plant-pest interactions. Specifically, salicylic acid and isoflavone based resistance was visualized in the soybean-aphid system and antibiotic diterpenoids in rice-bacterium interactions.
Insect-feeding birds may interfere with trophic interactions in plant–insect food webs, which may be particularly important in agroecosystems. Here, we studied how Eurasian Tree Sparrows (Passer ...montanus) affect aphids and their predators in cereal fields using bird exclusion experiments. The Tree Sparrows fed their nestlings with aphid antagonists. Hoverflies and ladybird beetles accounted for 77% of the food for the nestlings during peak aphid density. When birds were excluded, densities of hoverfly larvae, which were the most abundant aphid predator group in the cereals, were 4% higher in wheat and 45% higher in oat, while aphid densities were 24% lower in wheat and 26% lower in oat. The demonstrated disruption of biological control by mesopredators through bird predation may be a common phenomenon in cropping systems characterized by small-sized and abundant pest species. Management of biotic interactions such as biological control needs a broad food-web perspective, even in simplified agroecosystems.
Aphid Protected from Pathogen by Endosymbiont Scarborough, Claire L; Ferrari, Julia; Godfray, H. C. J
Science (American Association for the Advancement of Science),
12/2005, Letnik:
310, Številka:
5755
Journal Article
Recenzirano
Aphids are associated with several facultative bacterial endosymbionts that may influence their interactions with other organisms. We show here that one of the three most common facultative symbionts ...of pea aphid (Acyrthosiphon pisum), the bacterium Regiella insecticola, has a major effect on host resistance to a fungal pathogen. Experimental establishment of the bacterium in uninfected aphid clones led to higher survival after fungal attack. The bacteria also increased the aphid's inclusive fitness, because the presence of the symbiont reduced the probability of fungal sporulation on aphid cadavers, hence lowering the rate of transmission of the disease to nearby related aphids.
Summary
Environmentally induced changes in the epigenome help individuals to quickly adapt to fluctuations in the conditions of their habitats.
We explored those changes in Arabidopsis thaliana ...plants subjected to multiple biotic and abiotic stresses, and identified transposable element (TE) activation in plants infested with the green peach aphid, Myzus persicae. We performed a genome‐wide analysis mRNA expression, small RNA accumulation and DNA methylation
Our results demonstrate that aphid feeding induces loss of methylation of hundreds of loci, mainly TEs. This loss of methylation has the potential to regulate gene expression and we found evidence that it is involved in the control of plant immunity genes. Accordingly, mutant plants deficient in DNA and H3K9 methylation (kyp) showed increased resistance to M. persicae infestation.
Collectively, our results show that changes in DNA methylation play a significant role in the regulation of the plant transcriptional response and induction of defense response against aphid feeding.
Greenbug
Schizaphis graminum
(Rondani) is a serious insect pest that not only damages cereal crops, but also transmits several destructive viruses. The emergence of new greenbug biotypes in the ...field makes it urgent to identify novel greenbug resistance genes in wheat. CWI 76364 (PI 703397), a synthetic hexaploid wheat (SHW) line, exhibits greenbug resistance. Evaluation of an
F
2:3
population from cross OK 14319 × CWI 76364 indicated that a dominant gene, designated
Gb9
, conditions greenbug resistance in CWI 76364. Selective genotyping of a subset of
F
2
plants with contrasting phenotypes by genotyping-by-sequencing identified 25 SNPs closely linked to
Gb9
on chromosome arm 7DL. Ten of these SNPs were converted to Kompetitive allele-specific polymerase chain reaction (KASP) markers for genotyping the entire
F
2
population. Genetic analysis delimited
Gb9
to a 0.6-Mb interval flanked by KASP markers located at 599,835,668 bp (
Stars-KASP872
) and 600,471,081 bp (
Stars-KASP881
) on 7DL.
Gb9
was 0.5 cM distal to
Stars-KASP872
and 0.5 cM proximal to
Stars-KASP881
. Allelism tests indicated that
Gb9
is a new greenbug resistance gene which confers resistance to greenbug biotypes C, E, H, I, and TX1. TX1 is one of the most widely virulent biotypes and has overcome most known wheat greenbug resistance genes. The introgression of
Gb9
into locally adapted wheat cultivars is of economic importance, and the KASP markers developed in this study can be used to tag
Gb9
in cultivar development.
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