Ultrastructure of sieve element penetration by aphid stylets during electrical recording

Abstract

The probing activities of Brevicoryne brassicae (L.) on a host plant Brassica oleracea (L.) were electronically monitored using a direct current (DC) device. Two electrical penetration graphs are described, including a pattern, D + E, at two different potential levels; the normal level of pattern C, D + E(c), and the potential drop level, D+E(pd). Stylets were amputated during these patterns, sap exudation from the stumps was scored, and the penetrated leaf area with the remnants of the stylets were processed for EM. Sap was not produced from stylets cut during D + E(c). About 70% of stylets cut during the D+E(pd) pattern produced sap and in micrographs, stylet tips had pierced the sieve element plasmalemma and were found inside the cell lumen. This supports the earlier hypothesis that the D+E(pd) pattern is related to intracellular sieve element penetration. The relation of D + E(c) and D+E(pd) with ingestion is discussed. RÉSUMÉ Infrastructure de la pénétration des vaisseaux conducteurs par les stylets des aphides pendant l'enregistrement électrique Les pénétrations par Brevicoryne brassicae de la plante‐hôte Brassica oleracea étaient enregistrées électriquement au moyen d'un montage au courant continu. Deux signeaux sont décrits avec l'onde D+E à deux niveaux de potentiel électrique: le niveau normal de l'onde C, D+E(c), et un niveau bas après une chute de potentiel, D+E(pd). Au cours de ces deux ondes les stylets étaient amputés, on a pu observer le jaillisement de sève hors du moignon; on a ensuite préparé une partie de la feuille avec les restes des stylets pour le microscope électronique. Au cours de l'onde D+E(c) on observait aucune production de sève. Environ 70% des stylets amputés pendant l'onde D+E(pd) produisaient de la sève et dans deux de ces cas, dont les signeaux sont décrits, les pointes des stylets se trouvaient dans une cellule des vaisseaux conducteurs en ayant pénétrés le plasmalemme. Ces résultats confirment l'hypothèse antérieure, selon laquelle l'onde D+E(pd) est liée à une pénétration intracellulaire d'un vaisseau conducteur. La relation de l'onde D+E(c) et D+E(pd) avec l'ingestion par l'aphide est discutée.

Fine structure of aphid stylet routes in plant tissues in correlation with EPG signals

“…No callose is shown in punctured sieve elements, neither in necrotic cells nor in those that survived. Evert et al (1973) and Kimmins & Tjallingii (1985) also found no callose in sieve elements containing stylet tips.…”

“…In accordance with previous stylectomy during waveform E2 (Kimmins & Tjallingii, 1985;unpublished data), the stylet tips of probe A were located in a sieve element (Fig. 6).…”

“…(1973). Kimmins (1986Kimmins ( , 1988, Lopez-Abella et al (1988), Kimmins & Tjallingii (1985), Spiller et al (1985), as well as from EPG studies (Tjallingii, 1988). In contrast, many LM studies (Pollard, 1973) have suggested intracellular pathways as well.…”

Electronically monitored stylet penetration pathway of woolly apple aphid,Eriosoma lanigerum(Homoptera: Aphididae), on apple(Malus domestica)

“…After amplification, these voltage fluctuations are recorded as the EPG signal. Evidence supporting the correlation between electrical waveforms and different elements of the penetration behaviour of aphids feeding on soft plant tissues (unlignified tissues) has been reported (Kimmins & Tjallingii 1985;Spiller et al 1985;Tjallingii 1987;Tjallingii & Hogen Esch 1993). The EPG waveforms are characterised in terms of amplitude, frequency, and voltage level (van Helden & Tjallingii 2000).…”

A Diurnal Component to the Variation in Sieve Tube Amino Acid Content in Wheat

“…Sampling of phloem sap from individual STs can also be achieved using aphid stylectomy (Fisher and Frame, 1984). Aphids feed exclusively from the phloem (for review, see Will and van Bel, 2006), and a large literature shows that their stylet bundles penetrate and extract phloem sap from an individual ST (Kimmins and Tjallingii, 1985;Tjallingii and Esch, 1993). It is possible to sever the stylets of feeding aphids and collect samples of phloem sap (Unwin, 1978;Pritchard, 1996;Zhu et al, 2005), and studies have confirmed that the samples obtained represent pure ST sap (Tjallingii and Esch, 1993).…”