Angela Douglas
I am interested in how insects work. My research area is insect nutritional physiology (how insects process food for growth and reproduction), including the contribution of symbiotic microorganisms to insect nutrition.
Research foci
The obligate intracellular symbioses in insects
Our principal insect-microbial association is the symbiosis between aphids and the bacterium Buchnera. This symbiosis has excellent genomic resources, including the complete genome sequence of the pea aphid and its Buchnera symbiont, and it is amenable to nutritional physiological techniques. We have demonstrated that Buchnera provide aphids with essential amino acids, nutrients in short supply in the aphid diet of plant phloem sap. Currently, we are seeking to identify key gene products mediating the nutritional interactions between insect and bacteria and to establish their mode of action. This involves mining genomes for candidate genes, metabolic reconstruction, post-genomics (e.g. analysis of transcript profiles, proteomics, RNAi) and the physiology of nutrient utilization. We are motivated by the fundamental problem of how the bacteria have become integrated into the physiological system of the insect, and by the potential of the symbiosis as a target for insect pest management.
Carbon nutrition and osmoregulation in phloem-feeding insects
A major challenge for phloem-feeding insects is the high osmotic pressure of their sugar-rich diet that they are bound to ingest at high rates in order to extract sufficient nutrients other than sugar. We have established that the aphid gut is a major osmoregulatory organ through sugar transformations in the gut lumen and the controlled movement of water across the gut wall. Our research on the molecular physiology of the aphid gut is revealing genes, including an α-glucosidase and aquaporin, that play important roles in aphid carbon nutrition and osmoregulation. The key research problem is to establish how the functions of these genes are integrated to guarantee the sustained sugar supply and osmotic homeostasis in insects feeding on phloem sap of very variable sugar content. One goal of this research is to develop novel pest management strategies based on the disruption of osmoregulation in phloem-feeding insects.
Sterol nutrition of phloem-feeding insects
Insects (unlike vertebrates) cannot synthesize sterols and require a dietary supply to obtain cholesterol, a crucial component of cell membranes and precursor of escdysteroid hormones. We are currently investigating the composition of sterols in plant phloem sap and how aphids process the phytosterols that they ingest. Our program is also focused on modified sterols that can be deleterious to the insects, as a promising novel control strategy for aphid pests.
Drosophila-gut microbe interactions
We have established that the commensal microbiota in Drosophila guts is beneficial for the insect under standard laboratory conditions. Our purpose is to exploit the genomic tools available for Drosophila to identify how the microbiota interacts with insect nutrition and how it is managed by the insect immune system, as a model system for animal-gut microbe interactions, including the importance of gut microorganisms to human health.
A selection of recent publications
Douglas AE, Bouvaine S and Russell R, in press. How the insect immune system interacts with an obligate symbiotic bacterium. Proceedings of the Royal Society of London B.
Douglas AE, 2010. The Symbiotic Habit. Princeton University Press.
Wang Y, Carolan JC, Hao, F-H, Nicholson, J, Wilkinson TL and Douglas AE, 2010. Integrated metabonomic-proteomic analysis of an insect-bacterial symbiotic system. Journal of Proteome Research 9, 1257-1267. Pubmed link
The International Aphid Genomics Consortium, 2010. Genome sequence of the pea aphid Acyrthosiphon pisum. PLos Biology 8(2), e1000313. Journal link
Wilson ACC, Ashton PD, Calevro F, Charles H, Colella S, Febvay G, Jander G, Kushlan P, Macdonald SA, Schwartz J, Thomas GH and Douglas AE, 2010. Genomic insight into the amino acid relations of the pea aphid Acyrthosiphon pisum with its symbiotic bacterium Buchnera aphidicola. Insect Molecular Biology 19, s2, 249-258. Journal link
Ramsey JS, MacDonald SJ, Jander G, Nakabachi A, Thomas GH and Douglas AE, 2010. Genomic evidence for complementary purine metabolism in the pea aphid Acyrthosiphon pisum and its symbiotic bacterium Buchnera aphidicola. Insect Molecular Biology 19, s2, 241-248. Journal Link
Price DRG, Tibbles K, Shigenobu S, Smertenko A, Russell CW, Douglas AE, Fitches E, Gatehouse AMR and Gatehouse JA, 2010. Sugar transporters of the major facilitator superfamily in aphids; from gene prediction to functional characterisation. Insect Molecular Biology 19, S2, 97-112. Journal link
Hazell SP, Neve BP, Groutides C, Douglas AE, Blackburn TM and Bale JS, 2010. Hyperthermic aphids: insights into behaviour and mortality. Journal of Insect Physiology 56, 123-131. Pubmed link
Hawkes CV, Douglas AE and Fitter AH, 2010. Origin, local experience and the relative impact of biotic interactions on native and introduced Senecio species. Biological Invasions 12, 113-124.
Carolan JC, Fitzroy CF, Ashton PD, Douglas AE and Wilkinson TL 2009. The proteome of pea aphid saliva characterized by LC/MS-MS. Proteomics 9, 2457-2467. Pubmed
Thomas GH, Zucker J, MacDonald AJ, Goryanin I and Douglas AE 2009. A fragile metabolic network adapted for cooperation in the symbiotic bacterium Buchnera aphidicola. BMC Systems Biology 3, 24. Pubmed
Shakesby AJ, Wallace IS, Isaacs HV, Pritchard J, Roberts DM and Douglas AE, 2009. A water-specific aquaporin involved in aphid osmoregulation. Insect Biochemistry and Molecular Biology 39, 1-10. Pubmed
Gündüz EA and Douglas AE, 2009. Symbiotic bacteria enable insect to utilise a nutritionally-inadequate diet. Proceedings of the Royal Society of London B. 276, 987-991. Pubmed
Douglas AE 2009. The microbial dimension in insect nutritional ecology. Functional Ecology 23, 38-47.
The genome of the pea aphid Acyrthosiphon pisum (clone LSR1) has recently been sequenced by
The symbiotic bacteria Buchnera aphidicola (green) localized to aphid cells called bacteriocytes in the body cavity of aphids. [FISH micrograph by Simon Chandler]
The pea aphid gut sucrase gene APS1 (ACYPI000002) is expressed in the distal midgut (posterior to the stomach, S) as shown by in situ hybridization using an antisense DIG-labelled transcript of APS1 (A), with sense DIG-labeled transcript as negative control (B). The 68 kDa sucrase protein (arrow in C) was identified by MS/MS. [Price et al. 2007 Insect Biochemistry and Molecular Biology 37, 307-317]
RNAi in pea aphids. The aquaporin gene Aqp1 (ACYPI006387) is implicated in water cycling and osmoregulation in aphids, protecting the hemolymph (blood) from water loss to the gut and linked increase in osmotic pressure. When expression of AQP1 is reduced by RNAi (dsApAQP1), the hemolymph osmotic pressure increases significantly in aphids reared on diets with different sucrose concentrations [F (1,31 df) = 5.04, 0.05>p>0.01]. dsGFP (dsRNA of the green fluorescent protein-citrine) was used as negative control. [Shakesby et al. Insect Biochemistry and Molecular Biology 39, 1-10] 
3D reconstruction of the chaperonin protein GroEL monomer of Buchnera aphidicola, the symbiotic bacterium of aphids, compared to the structure of E. coli GroEL. The few differences in predicted structure are shown in blue. [Sophie Bouvaine and Angela Douglas, unpublished]