Application of Electrical Penetration Graph (EPG) technique in studies on plant responses to aphid probing
Aphids feed on the phloem sap using their specialised sucking-piercing mouthparts, which penetrate plant tissues intercellularly until they reach vascular tissue. During penetration, aphid stylets puncture plant mesophyll cells when small samples of sap are taken, probably from the cell’s protoplast and vacuole. Aphid probing and feeding induce various defense signaling mechanisms in plants. The signals responsible for the activation of plant defenses to aphid feeding are not only mechanical, but also chemical, through the action of particular molecules commonly called elicitors which are present in aphid saliva. In the course of co-evolution, aphids developed an array of mechanisms to cope with plant responses to herbivore attack. The research is concentrated upon aphid behavioural reactions to aphid-derived changes in plant physiology.
Aphid behaviour during stylet penetration in plant tissues can not be observed directly. Therefore, the Electrical Penetration Graph (EPG) technique is applied. In this experimental set-up, aphid and plant are made parts of an electric circuit, which is completed when the aphid inserts its stylets into the plant. Weak voltage is supplied in the circuit, and all changing electric properties are recorded as EPG waveforms that can be correlated with aphid activities and stylet position in plant tissues (W.F. Tjallingii, EPG-Systems; Dillenburg 12, 6703 CJ Wageningen, The Netherlands). Parameters that derive from EPG recordings are good indicators of preingestional and ingestional factors affecting aphid probing and feeding.
Mai VC, Drzewiecka K., Jeleń H., Narożna D., Rucińska-Sobkowiak R., Kęsy J., Floryszak-Wieczorek J., Gabryś B., Morkunas I. 2014. Differential induction of Pisum sativum defense signaling molecules in response to pea aphid infestation. Plant Science 221-222: 1-12.
Morkunas I., Mai V. Ch., Gabryś B. 2011. Phytohormonal signaling in plant responses to aphid feeding. Acta Physiologiae Plantarum. 33(6): 2057-2073.
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