Biology subjects

Bos, J. I. B.

Publications and source records attributed to Bos, J. I. B..

4 recordsLinked to original sources

bioRxiv2026

An aphid effector pair forms a hetero-oligomeric complex important for protein stability and activity

During disease and infestation, pathogens and pests deliver effectors inside their host to manipulate host responses, leading to immune suppression and altered nutrient availability. To be successful, pathogens and pests can produce and secrete large repertoires of effectors, consisting of up to hundreds of proteins. While effector virulence activities are usually studied in isolation, effectors can function together or cooperate to regulate transport and/or activity. An important example is the suppression of effector avirulence activity by plant pathogenic microbe effectors. Moreover, some effectors can physically associate with target host proteins and promote virulence. Here we explored the interaction of a conserved and co-regulated effector pair in aphids. Using a combination of computational modelling and crystallography combined with functional assays, we reveal a novel type of oligomeric assembly of the paired aphid effectors in a hexameric/octameric complex. Our data indicate that different oligomerization states exist among orthologs of this effector complex, suggesting that dynamic dissociation or subunit exchange may occur. Structure-based mutagenesis revealed that complex formation is essential for both effector protein stability and the in planta activity of one of these proteins. These findings emphasize the significance of effector hetero-oligomerization at the plant-insect interface, consistent with the model that this effector pair is an evolutionarily conserved module across aphid species.

biochemistry↗

bioRxiv2019

A fitness cost resulting from Hamiltonella defensa infection is associated with altered probing and feeding behaviour in Rhopalosiphum padi

Aphids frequently associate with facultative endosymbiotic bacteria which influence aphid physiology in myriad ways. Endosymbiont infection can increase aphid resistance against parasitoids and pathogens, modulate plant responses to aphid feeding, and promote aphid virulence. These endosymbiotic relationships can also decrease aphid fitness in the absence of natural enemies or when feeding on less suitable plant types. Here, we use the Electrical Penetration Graph (EPG) technique to monitor feeding behaviour of four genetically-similar clonal lines of a cereal-feeding aphid, Rhopalosiphum padi, differentially infected (+/-) with the facultative protective endosymbiont, Hamiltonella defensa, to understand how physiological processes at the aphid-plant interface are affected by endosymbiont infection. Endosymbiont-infected aphids exhibited altered probing and feeding patterns compared with uninfected aphids, characterised by a two-fold increase in the number of plant cell punctures, a 50% reduction in the duration of each cellular puncture, and a greater probability of achieving sustained ingestion of plant phloem. Feeding behaviour was altered further by host plant identity: endosymbiont-infected aphids spent less time probing into plant tissue, required twice as many probes into plant tissue to reach plant phloem, and showed a 44% reduction in phloem ingestion when feeding on the partially-resistant wild relative of barley, Hordeum spontaneum 5, compared with a commercial barley cultivar. These observations might explain reduced growth of H. defensa-infected aphids on the former host plant. This study is the first to demonstrate a physiological mechanism at the aphid-plant interface contributing to endosymbiont effects on aphid fitness on different quality plants through altered aphid feeding behaviour.\n\nSummaryReduced performance of aphids infected with a common facultative endosymbiont on poor quality plants may be explained by changes in aphid probing behaviour and decreased phloem sap ingestion.

physiology↗

bioRxiv2019

Partial-resistance against aphids in wild barley reduces the oviposition success of the generalist parasitoid, Aphidius colemani

Aphids are significant agricultural pests of cereal crops with a worldwide distribution. The control of aphids in agricultural systems is currently heavily reliant on insecticidal compounds, but it is becoming increasingly apparent that chemical-based control of agricultural pests has far-reaching unintended consequences on agro-ecosystems. As a result, more sustainable means of aphid control are becoming increasingly desirable. Potential options include increasing plant resistance against aphids, promoting biocontrol, and the combined use of both strategies. When used together it is important to understand how, and to what extent, increased plant resistance against aphids affects the success of biocontrol agents. In this current study, we examine how partial-resistance against cereal aphids in a wild relative of barley, Hordeum spontaneum 5 (Hsp5), affects the success of the common parasitoid of cereal aphids, Aphidius colemani. We show that the parasitism success of A. colemani attacking nymphs of the bird cherry-oat aphid, Rhopalosiphum padi, contained on Hsp5 is reduced compared with the parasitism success of wasps attacking R. padi nymphs feeding on a susceptible modern cultivar of barley, H. vulgare cv. Concerto. Explanta parasitism assays showed that the in parasitoid success is a direct effect of the plant environment (such as differential architectural traits), rather than an indirect effect dur to a decrease in aphid suitability resulting from increased resistance against aphids in Hsp5. Our study highlights the importance of understanding the direct and indirect effects of plant resistance against aphids on biocontrol strategies.

plant biology↗

bioRxiv2018

Partial-resistance against aphids in wild barley involves phloem and mesophyll-based defences

Aphids, including the bird cherry-oat aphid (Rhopalosiphum padi), are significant agricultural pests. Aphid populations are typically controlled using insecticides, but there is increasing demand for more sustainable pest management practices. The wild relative of barley, Hordeum spontaneum 5 (Hsp5) has been described as partially-resistant to R. padi. Partial-resistance is proposed to involve higher thionin and lipoxygenase gene expression. However, the underlying mechanistic processes are unknown. In this study we compared Hsp5 with a susceptible cultivar of barley (Concerto) to test the extent to which partial-resistance affects aphid fitness. We used the electrical penetration graph technique to monitor R. padi feeding patterns to elucidate the tissue location of partial-resistance factors alongside molecular and biochemical analyses to identify potential mechanisms. We show that partial-resistance in Hsp5 extends to three aphid species and is mediated by phloem/mesophyll-based factors, leading to a three-fold increase in the time aphids take to establish sustained phloem ingestion. Partial-resistance likely involves elevated expression of defence and phytohormone genes alongside altered phloem amino acid composition. Further work is required to establish the function of these traits, however this study highlights plant tissues which are important in conferring broad-spectrum partial-resistance against aphids in barley.\n\nHighlightPartial-resistance against aphids in wild barley is based in the mesophyll and vascular tissue and is potentially associated with higher basal defence gene expression and altered phloem amino acid composition.

plant biology↗