Plant-aphid interaction: local and systemic effects on plant physiology and gene expression

Dilks, Teresa (2015). Plant-aphid interaction: local and systemic effects on plant physiology and gene expression. University of Birmingham. Ph.D.

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Abstract

Aphids are economically important pests of glasshouse and temperate crops. By investigating the effects of aphid feeding on plant performance and by understanding the host-pest relationship, novel defence strategies can be devised. The effect of \(Rhopalosiphum\) \(padi\) (the bird cherry-oat aphid) feeding on young \(Hordeum\) \(vulgare\) (barley) plants was investigated. Particular emphasis was placed on changes within the sieve element (SE) because aphids are phloem-feeding insects.

Aphid infestation significantly reduced host plant growth rate. High performance liquid chromatography showed a local elevation of leaf calcium levels in infested leaves. Calcium, sulphate and magnesium levels were all elevated systemically by aphid feeding, whilst nitrate levels decreased. Aphid feeding increased the duration of phloem sap exudation from severed stylets but did not alter exudation rate.

Electrical penetration graph studies demonstrated that the duration of SE sap ingestion was reduced, and the time aphid stylets spent in pathway through the leaf increased, on pre-infested plants. The time taken for aphids to locate the SE did not increase, however, suggesting that the inhibitory effect was phloem-localised.

In an attempt to elucidate the transcriptomic response to aphid attack, microarrays were performed on infested and uninfested barley plants. Gene expression changes in the first and second leaves were compared to determine the local and systemic effects, respectively. The differentially expressed genes have putative roles in defence, hormone signalling, cell wall remodelling, metabolism, transport and regulation of transcription and translation. The general response was a local suppression and systemic induction of plant defences.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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