Probiotic effects of beta-glucuronidase on the peach-potato aphid Myzus persicae (Aphididae)

Evaluation of Hamiltonella on Aphis gossypii fitness based on life table parameters and RNA sequencing

BACKGROUND

Insect endosymbionts are widespread in nature and known to play key roles in regulating host biology. As a secondary endosymbiont, bacteria in the genus Hamiltonella help cotton aphids (Aphis gossypii) defend against parasitism by parasitoid wasps, however, the potential negative impacts of these bacteria on cotton aphid biology remain largely unclear.

RESULTS

This study aims to evaluate the potential impacts of Hamiltonella on the growth and development of cotton aphids based on life table parameters and RNA sequencing. The results showed that infection with Hamiltonella resulted in smaller body type and lower body weight in aphids. Compared to the control group, there were significant differences in the finite and intrinsic rates of increase and mean generation time. Furthermore, the RNA sequencing data revealed that the genes related to energy synthesis and nutrient metabolism pathways were significantly downregulated and genes related to molting and nervous system pathways were significantly upregulated in the Hamiltonella population.

CONCLUSION

Our results confirm that Hamiltonella retarded the growth and development of cotton aphids accompanied by the downregulation of genes related to energy synthesis and nutrient metabolism, which provides new insights into aphid-symbiont interactions and may support the development of improved aphid management strategies. © 2022 Society of Chemical Industry.

Resistance of Seven Cabbage Cultivars to Green Peach Aphid (Hemiptera: Aphididae)

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is an important pest of many crops in the world and a vector of more than 100 plant viruses. It is a major pest of Brassica vegetables such as Chinese cabbage in northern China. Chemical control is extensively used to manage this aphid around the world; however, development of insecticide resistance has been a major obstacle facing growers. Host plant resistance in Chinese cabbage against M. persicae has not been reported yet. In this study, we investigated the resistance categories in seven Chinese cabbage cultivars against M. persicae. The resistance categories of these cultivars included antixenosis, antibiosis, and tolerance related to leaf color and wax content. The cultivar 'Yuanbao' had antibiotic and tolerance effects on the aphid. The rate of intrinsic increase (rm) of M. persicae was lower on Yuanbao compared with the other six cultivars. Yuanbao also had the highest antibiosis against the aphid. The aphid preferred 'Qingan 80', which had the highest wavelength (green) in leaf color. The highest wax content was found in Yuanbao, which had a significantly negative correlation with the preference of M. persicae. The cabbage cultivar Yuanbao was resistant to M. persicae and could be used in the development of integrated pest management (IPM) programs against the aphid in the field.

Identification of genes involved in wild crucifer Rorippa indica resistance response on mustard aphid Lipaphis erysimi challenge

Mustard aphid, Lipaphis erysimi (L.) Kaltenbach is a perpetual annual threat in the cultivation of rapeseed- mustard (Brassica spp.) crop in tropical and sub-tropical climate. Cultivated Brassica germplasm has failed so far to provide any source of resistance. Wild germplasm is a potential source of resistance against many threatening herbivores. On wild germplasm screening, we noted that the wild crucifer Rorippa indica (L.) Hiern confers resistance against L. erysimi. In the present study L. erysimi challenged transcriptome of R. indica was compared to un-infested R. indica sample to get a molecular insight about the aphid resistance mechanism and identify the candidate defense response genes. Cloning, sequencing and in silico sequence analysis of complimentary DNA amplified fragment length polymorphism identified 116 differentially expressed transcript derived fragments revealed thirty candidates which are from different functional categories including redox regulation, signalling, photosynthesis, structure, metabolism, defense response as well as a few of unknown function. Twenty four identifications were then studied by quantitative real time RT PCR analysis at 6, 12, 24 and 48 hour time point post infestation to understand the early-to-late defense response through their relative gene expression profiles. Seventeen fragments showed significant up or down regulation at p<0.05 level. The response was influenced by different phytohormonal signalling pathways simultaneously. The candidate defense response expressed sequence tags specifically for the resistance genes identified in this study have implication in building desired mustard aphid resistance in susceptible rapeseed-mustard plants in future. This is the first molecular report on crucifer defense response against mustard aphid L. erysimi.

Effects of Manduca sexta allatostatin and an analogue on the peach-potato aphid Myzus persicae (hemiptera: aphididae) and degradation by enzymes in the aphid gut

The oral toxicity of the C-type allatostatin, Manduca sexta allatostatin (Manse-AS) and the analogue δR³δR⁵Manse-AS, where R residues were replaced by their D-isomers, were tested against the peach-potato aphid Myzus persicae by incorporation into an artificial diet. Both peptides had significant dose-dependent effects on mortality, growth, and fecundity compared with control insects. The analogue, δR³δR⁵Manse-AS, had an estimated LC₅₀ of 0.31 µg/µl diet and was more potent than Manse-AS (estimated LC₅₀ of 0.58 µg/µl diet). At a dose of 0.35 µg δR³δR⁵Manse-AS/µl diet, 76% of the aphids were dead after 6 days and all were dead after 10 days. In comparison, three times the dose of Manse-AS was required to achieve 74% mortality after 8 days and 98% mortality after 16 days. The degradation of both peptides by extracts prepared from the gut of M. persicae was investigated. The estimated half-life of Manse-AS, when incubated with the gut extract from M. persicae, was 31 min. Degradation was due to a cathepsin L-like cysteine protease, carboxypeptidase-like activity, endoprotease activity with glutamine specificity, pyroglutamate aminopeptidase activity, and possibly trypsin-like proteases. The half-life of the δR³δR⁵ Manse-AS analogue was enhanced (73 min) with the D-isomers of R appearing to prevent cleavage around the R residues by cathepsin L-like cysteine proteases or from trypsin-like proteases. The greater stability of the analogue may explain its increased potency in M. persicae. This work demonstrates the potential use of Manse-AS and analogues, with greater resistance to enzymatic attack, in aphid control strategies.

Phytase transgenic maize does not affect the development and nutrition utilization of Ostrinia furnacalis and Helicoverpa armigera

Use of transgenic maize expressing phytase in seeds as feedstuff can greatly increase phosphate availability to livestock and poultry. Because phosphorus is an essential mineral for all living organisms, growing of phytase transgenic maize may affect the performance of the arthropod community in maize fields. We conducted a preliminary study to assess the potential effects of phytase transgenic maize (BVLA430101) on two herbivore species, Ostrinia furnacalis (Guenée) and Helicoverpa armigera (Hübner), both of which are directly exposed to high concentrations of phytase caused by ingestion of transgenic maize kernels. Our results showed that for both species, survival and duration of the first and second instars and fresh weight of the third instar were not affected when fed transgenic phytase maize kernels compared with those fed nontransformed near isoline kernels. Similarly, there was no statistical difference detected for the same life table parameters when the herbivores were fed artificial diet containing either transgenic phytase maize meal or nontransformed maize meal. In addition, the nutrition utilization of the two species was evaluated with the same diet treatments by comparing the following indices: relative food consumption rate (RCR), relative metabolic rate (RMR), efficiency of approximate digestibility (EAD), efficiency of conversation of ingested food (ECI), and efficiency of conversation of digested food (ECD). No statistical difference was detected for any index of either species between transgenic maize and nontransformed maize treatments. These results provide useful baseline information for further studies to assess the potential effects of phytase transgenic maize on other arthropods in maize fields.

Differential aphicidal effects of chitinase inhibitors on the polyphagous homopteran Myzus persicae (Sulzer)

Four chitinase inhibitors, cyclo-(Proline-Tyrosine), cyclo-(Histidine-Proline), allosamidin and psammaplin A, were selected for in vitro feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions. Artificial diets were used to provide chitinase inhibitors at 10, 50 and 100 microg mL(-1) to M. persicae. Except for cyclo-(Proline-Tyrosine), which did not modify aphid demographic parameters, chitinase inhibitors induced differential aphicidal effects on M. persicae. At all doses, cyclo-(Histidine-Proline) induced significant effects affecting daily fecundity, intrinsic rate of natural increase (r(m)) and doubling time of population. When compared with the control diet, allosamidin decreased nymph survival and daily fecundity, increasing the doubling time of population from 1 to 1.5 days. Psammaplin A was the most toxic inhibitor when delivered via artificial diet, as it induced the death of all aphids reared at 50 and 100 microg mL(-1). The results demonstrate the potential use of chitinase inhibitors as aphid management tools.

Unexpected effects of chitinases on the peach-potato aphid (Myzus persicae Sulzer) when delivered via transgenic potato plants (Solanum tuberosum Linné) and in vitro

With the aim of producing insect-resistant potato plants, internode explants of Solanum tuberosum L. cv. Désirée were transformed with an Agrobacterium strain C58pMP90 containing an insect (Phaedon cochleariae: Coleoptera, Chrysomelidae) chitinase gene and the neomycin phosphotransferase (nptII) gene as selectable marker, both under the control of the viral CaMV 35S promoter. Three transformed potato lines (CH3, CH5 and CH25) exhibiting the highest chitinolytic activities were selected for feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions. Aphids fed on transgenic potato plants showed a reduced pre-reproductive period and an enhanced daily fecundity. Transgenic potato lines did not affect nymphal mortality, but improved several biological parameters related to aphid population's growth. Artificial diets were used to provide active (1, 10, 100 and 500 microg ml(-1)) and inactive (500 microg ml(-1)) bacterial (Serratia marcescens) chitinase to M. persicae. These compounds increased nymph survival at all active chitinase doses when compared to the control diet, while inactive chitinase did not. Although the pre-reproductive period was slightly shortened and the daily fecundity slightly higher, active and inactive chitinase provided as food led a reduction from 1 to 1.5 day population's doubling time. Therefore chitinase activity was responsible for the probiotic effects on aphids. Our results question the relevance of a chitinase-based strategy in the context of potato culture protection.

Effects of plant protease inhibitors, oryzacystatin I and soybean Bowman-Birk inhibitor, on the aphid Macrosiphum euphorbiae (Homoptera, Aphididae) and its parasitoid Aphelinus abdominalis (Hymenoptera, Aphelinidae)

Transgenic plants expressing protease inhibitors (PIs) have emerged in recent years as an alternative strategy for pest control. Beneficial insects such as parasitoids may therefore be exposed to these entomotoxins either via the host or by direct exposure to the plant itself. With the objective of assessing the effects of PIs towards aphid parasitoids, bioassays using soybean Bowman-Birk inhibitor (SbBBI) or oryzacystatin I (OCI) on artificial diet were performed on Macrosiphum euphorbiae-Aphelinus abdominalis system. OCI significantly reduced nymphal survival of the potato aphid M. euphorbiae and prevented aphids from reproducing. This negative effect was much more pronounced than with other aphid species. On the contrary, SbBBI did not affect nymphal viability but significantly altered adult demographic parameters. Enzymatic inhibition assays showed that digestive proteolytic activity of larvae and adults of Aphelinus abdominalis predominantly relies on serine proteases and especially on chymotrypsin-like activity. Immunoassays suggested that OCI bound to aphid proteins and accumulated in aphid tissues, whereas SbBBI remained unbound in the gut. Bioassays using M. euphorbiae reared on artificial diets supplemented with both OCI and SbBBI showed a fitness impairment of Aphelinus abdominalis that developed on intoxicated aphids. However, only SbBBI was detected in parasitoid larvae, while no PI could be detected in adult parasitoids that emerged from PI-intoxicated aphids. The potential impact of PI-expressing plants on aphid parasitoids and their combined efficiency for aphid control are discussed.