Horizontal transmission (from <i>R⁺</i> whiteflies to wasps) and vertical transmission (from <i>R⁺</i>wasps to progeny) of <i>Rickettsia</i> to males and females of <i>Er. emiratus</i> (top), <i>Er. eremicus</i> (middle) and <i>En. pergandiella</i> (bottom).

<p>‘P’ are <i>R⁻</i> wasps that were exposed to <i>R⁺</i> whiteflies for 24 hrs (horizontal transmission via host feeding and/or honeydew), ‘F₁’ are their resulting progeny that developed in <i>R⁺</i> hosts (also horizontal transmission), and ‘F₂’ are progeny of F₁ that were exposed to <i>R⁻</i> hosts (vertical transmission). The numbers above the columns are the sample size, <i>n</i>, from which the proportion of infected wasps was calculated. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004767#pone-0004767-g001" target="_blank">Fig. 1</a> for this experiment's set-up.</p

FISH of <i>Er. emiratus</i> stained with <i>Rickettisa</i> specific probe (blue).

<p>Left panel-<i>Rickettsia</i> probe fluorescent channel; right panel- overlay of fluorescent and brightfield channels. Arrows pointing to parasitoid gut. A- parasitoid larva (dark, ovoid sphere in the center of the host). Note <i>Rickettsia</i> in the parasitoid gut, as well in the whitefly's body remnants, surrounding the parasitoid. B- parasitoid pre-pupa. C- parasitoid pupae (note the autofluorescence of the anus and mouthpart); 1C, right image- brightfield channel only. D- parasitoid adult abdomen.</p

<i>Rickettsia</i> (white arrows) in <i>Er. eremicus</i> follicular epithelial cell (FC).

<p>The gap between the follicular epithelial cell and the oocyte (the transition zone - TZ) is due to oocyte resorption. N-nucleus; EnC- endochorion; ExC- Exochorion; VE- Vitellin envelope.</p

A diagram illustrating the design of experiment 7, transmission of symbionts from <i>B. tabaci</i> to parasitoids, and 8, vertical transmission of symbionts in parasitoids.

<p>Infection status is indicated either by red “+” sign or blue “−” sign. R = <i>Rickettsia</i>, H = <i>Hamiltonella</i>. TRT = treatment. Whitefly hosts are illustrated as small yellow ovals on the (green) leaf disks. To test transmission of symbionts from <i>B. tabaci</i> to parasitoids, one female parasitoid was introduced to each leaf disk for 24 h, after which they were tested by PCR. From the emerging F₁, one or two females from each replicate were used to continue to the vertical transmission experiment, while the rest of the cohort was tested by PCR (two-five from each cohort). The emerging F₂ were all collected and two-five from each cohort were tested by PCR.</p

<i>Rickettsia</i> (white arrows) in <i>Er. eremicus</i> germarium area, between nuclei of stem/pre-follicle/nurse cells as well as outside the ovary, next to the Tunica propria (TP).

<p>Note mature oocyte on the bottom left corner area. N-nucleus; EnC- endochorion; ExC- Exochorion; VE- Vitellin envelope.</p

<i>Rickettsia</i> (bordered) outside <i>Er. eremicus</i> ovary envelope, the tunica propria (TP).

<p>FC- follicular epithelial cell; EnC- endochorion; ExC- Exochorion; VE- Vitellin envelope; Tr- Trachea.</p