In a frequency tuned pressure difference receiver, such as the cricket auditory pathway, phase differences generated within the auditory trachea have been shown to be of crucial importance [27], [28].
Also the total time of the pathway phase was similar on Ws and mutant 3790 (Table 1).
Cell puncturing led to the pathway phase in which the stylet penetrated between cells en route to the vascular tissue [ 35].
The pathway phase represents insect's efforts in navigating the phloem and preparing to ingest sap from sieve elements [ 16, 17].
In the four-hour EPG record, total number and duration of the nonpuncturing phase, time to the first cell puncturing or the first pathway phase, and total number and duration of the pathway phase were all similar in HrpNEa-treated plants as in control plants (Table 1).
The pathway phase may be also connected with the xylem phase, indicating stylet penetration of the xylem in the vascular tissue [ 16], but xylem phase was not found in this study.
This was supported by the fact that the phloem phase of M. persicae on SKS13 overexpressing plants was delayed in time and reduced in length, while the length of the pathway phase was not significantly different from the control.
In the first hour, especially, the nonpuncturing phase was more frequent with longer duration while the pathway phase was more but shorter under the HrpNEa treatment condition compared with control.
Waveform C represents the pathway phase, when the aphid stylet is penetrating through the leaf tissue; waveform E2 represents phloem sap ingestion; Waveform F is associated with penetration difficulties; and waveform G indicates active uptake of water from the xylem.
Therefore, during the first two phases of the transcriptional program, E2 induces the expression of a battery of sequence-specific transcriptional regulators (phase 1; Figure 4C) and then induces the expression of genes in the protein synthesis pathway (phase 2; Figure 5).
