In order to assess the impact of manipulated VOCs on plant- plant communications, we generated transgenic plants that constitutively biosynthesize and emit VOCs. We prepared gene constructs consisting of lima bean (E)-b-ocimene synthase PlOS inserted downstream of the constitutive 35S cauliflower mosaic viral (CMV) promoter, and successfully generated a set of independent transgenic tobacco lines. Four representative exam- ples exhibiting substantial trans-gene (PlOS) expression and (E)-b- ocimene emission are shown in Figure 1. Their emissions ranged between 166 ng [gram fresh weight (gFW h21) (NtOS4) and 384 ng [gFW h21] (NtOS2), whereas WT tobacco plants emitted these compounds at only extremely low levels (,2 ng [gFW h21]) (Figure 1C). The levels of (E)-b-ocimene emitted by the above transgenic plants were sufficiently relevant to those emitted by WT lima bean plants: e.g., about 3,000 ng [gFW h21] and 30 ng [gFW h21] in response to feeding by Spodoptera littoralis [23] and T. urticae (see below), respectively. In addition, none of the transgenic lines exhibited any differences in their detectable morphology or their levels of emission of VOCs other than (E)-b-ocimene.