Aphid saliva

Authors
Citation
Pw. Miles, Aphid saliva, BIOL REV, 74(1), 1999, pp. 41-85
Citations number
211
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Biology,"Experimental Biology
Journal title
BIOLOGICAL REVIEWS OF THE CAMBRIDGE PHILOSOPHICAL SOCIETY
ISSN journal
1464-7931 → ACNP
Volume
74
Issue
1
Year of publication
1999
Pages
41 - 85
Database
ISI
SICI code
1464-7931(199902)74:1<41:AS>2.0.ZU;2-B
Abstract
Within the Aphidoidea, most species of Aphididae, as long as they are in sm all numbers and not carrying plant viruses, do little perceptible damage to their food plants. In species that cause toxicoses, it is usually assumed that some component of the saliva must be responsible. Paradoxically, howev er, the salivary enzymes of Aphididae are similar to those that already occ ur in plants-oxidases and enzymes that depolymerize polysaccharides-and the salivary enzymes are injected in very small amounts relative to their coun terparts in the plant. Damage to plants triggers defensive, biochemical res ponses, and it is suggested that the injected enzymes serve mainly to diver t or counter responses at the immediate interface of stylets and plant tiss ues. The saliva of Aphididae contains non-enzymic, reducing compounds which , in the presence of oxidases, can combine with and inactivate defensive ph ytochemicals-including those released in response to damage and transported in the phloem sieve tube sap on which Aphididae feed. Salivary and gut oxi dases deactivate ingested phytochemicals by oxidative polymerization. Aphid idae inject saliva into sieve tubes before sustained ingestion of sap, and this saliva has been presumed to condition the sieve tubes, but in what way remains unclear. It is suggested that there is a dynamic biochemical inter action between aphids and plants; that the interaction is usually well bala nced for most of the Aphididae; hence, no outcome is readily observable. Wh ere a significant imbalance occurs, however, either the aphid is unable to feed, i.e. the plant is resistant, and/or the aphid does not effectively co unter a hypersensitive response. Not all plant responses are disadvantageou s to aphids. Gall-forming Aphidoidea trigger and control abnormal growth in the plant to the insects' advantage, possibly by eliciting vigorous oxidat ion in selective meristematic tissues, thereby limiting supply of molecular oxygen and inhibiting oxygen-dependent growth-controls. Current problems a nd possible approaches for further research are reviewed.