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Abstracti mb_918 97..112Analysis of the pea aphid (Acyrthosiphon pisum) genome using signatures specific to the Major Facilitator Superfamily (Pfam Clan CL0015) and the Sugar_tr family (Pfam Family PF00083) has identified 54 genes encoding potential sugar transporters, of which 38 have corresponding ESTs. Twenty-nine genes contain the InterPro IPR003663 hexose transporter signature. The protein encoded by Ap_ST3, the most abundantly expressed sugar transporter gene, was functionally characterized by expression as a recombinant protein. Ap_ST3 acts as a low-affinity uniporter for fructose and glucose that does not depend on Na + or H + for activity. Ap_ST3 was expressed at elevated levels in distal gut tissue, consistent with a role in gut sugar transport. The A. pisum genome shows evidence of duplications of sugar transporter genes.Keywords: facilitated substrate transport, transmembrane protein, gut metabolism, in situ localization, yeast expression system.

Abstract. 1. Aphid populations on agricultural crops in temperature regions collapse over a few days from peak numbers to local extinction soon after midsummer (e.g. mid-July in the U.K.). The populations recover 6-8 weeks later. There is anecdotal or incidental evidence of an equivalent mid-season population crash of aphids on grasses and forbs in natural vegetation.2. The ecological factors causing the mid-season population crash of aphids include a decline in plant nutritional quality and increased natural enemy pressure as the season progresses. Extreme weather events, e.g. severe rainstorms, can precipitate the crash but weather conditions are not a consistent contributory factor.3. The population processes underlying the crash comprise enhanced emigration, especially by alate (winged) aphids, depressed performance resulting in reduced birth rates, and elevated mortality caused by natural enemies.4. Mathematical models, previously applied to aphid populations on agricultural crops, have great potential for studies of aphid dynamics in natural vegetation. In particular, they can help identify the contribution of various ecological factors to the timing of the population crash and offer explanations for how slow changes in population processes can result in a rapid collapse of aphid populations.

sucrose. It is concluded that the osmoregulatory response of aphids to diets and plants are comparable, and, more generally, that the feeding and osmoregulatory capabilities of the aphids are compatible with the phloem sugar levels commonly encountered by aphids feeding on plants.

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