Aphid watery saliva counteracts sieve-tube occlusion: a universal phenomenon?

Abstract

SUMMARY Ca 2+-binding proteins in the watery saliva of Megoura viciae counteract Ca 2+ -dependent occlusion of sieve plates in Vicia faba and so prevent the shut-down of food supply in response to stylet penetration. The question arises whether this interaction between aphid saliva and sieve-element proteins is a universal phenomenon as inferred by the coincidence between sieve-tube occlusion and salivation. For this purpose, leaf tips were burnt in a number of plant species from four different families to induce remote sieve-plate occlusion. Resultant sieve-plate occlusion in these plant species was counteracted by an abrupt switch of aphid behaviour. Each of the seven aphid species tested interrupted its feeding behaviour and started secreting watery saliva. The protein composition of watery saliva appeared strikingly different between aphid species with less than 50% overlap. Secretion of watery saliva seems to be a universal means to suppress sieve-plate occlusion, although the protein composition of watery saliva seems to diverge between species.

An aphid's Odyssey – the cortical quest for the vascular bundle

“…Hewer, A. Becker and A. J. E. van Bel A DC EPG Giga-8 system and PROBE software (W. F. Tjallingii, Wageningen Agricultural University, Wageningen, The Netherlands) was used as described previously (Will et al, 2008;Will et al, 2009) to monitor M. viciae feeding on the youngest mature internode of a V. faba stem. EPG recordings were made from three classes of aphids: (i) aphids directly transferred from the breeding plant to the EPGrecorded plant (i.e.…”

“…To investigate the effects of a modified composition of sieve-tube sap, adult individuals of A. fabae were prepared for EPG as described previously (Will et al, 2008;Will et al, 2009). EPG recordings (8h duration) were started immediately after placing an aphid onto the hypocotyl hook of a R. communis seedling that had had its cotyledons pre-incubated in sugar solutions for 2h (Fig.2), as described above, with 6 replicates for each treatment.…”

“…As a consequence, aphid and plant act as a variable resistor (e.g. Walker, 2000;Will et al, 2009). The resulting signal waveforms have been correlated with distinct foraging activities (Tjallingii, 1985;Tjallingii, 1988;Tjallingii and Hogen Esch, 1993;Prado and Tjallingii, 1994;Tjallingii, 1994;Tjallingii, 1995a;Tjallingii, 1995b), such as saliva secretion or sap ingestion.…”

Plant cues for aphid navigation in vascular tissues

“…The basin was filled to its maximum in order to keep the plastic film stretched, which was sealed with a ring of BlueTac ® and fixed with a screwable plastic fixing device onto the basin. Adult and apterous individuals of M. persicae were prepared for EPG as described previously Will et al, 2009). EPGs lasted 8h, starting directly after putting aphids onto the plastic film, and were repeated eight times each.…”

“…Sieve-tube sap is withdrawn by specialized aphid mouth parts (stylets) (Auclair, 1963;Miyazaki, 1987). Prior to ingestion, aphids secrete watery saliva, probably to interfere with plant occlusion reactions induced by stylet damage (Will and van Bel, 2006;Will et al, 2007;Will et al, 2009;Carolan et al, 2009).…”