Chiral Chemopolymorphism in the Monoterpenes of Pistacia palaestina Leaves and Galls.

Pistacia palaestina Boiss. is a common tree in the Mediterranean maquis. The leaves of this plant accumulate defensive monoterpenes, whose levels greatly increase in galls induced by the aphid Baizongia pistaciae. We previously found a significant chemopolymorphism in monoterpene content among individual trees, but the chirality of these monoterpenes was unknown. Although most plant species specifically accumulate one enantiomeric form of a given compound, P. palaestina individuals display chemopolymorphism in the chirality of the key monoterpenes accumulated. We report here a marked enantiomeric variation for the limonene, α- and ß-pinene, camphene, sabinene, δ-3-carene, and terpene-4-ol content in leaves and galls of nine different naturally growing P. palaestina trees. Interestingly, insect-induced gall monoterpene composition is an augmentation of the specific enantiopolymorphism originally displayed by each individual tree.

The dynamics and the timeline of speciation in the gall-forming aphid Geoica spp. within and among Pistacia host tree species.

Trees of the genus Pistacia serve as obligate hosts for gall-forming aphids (Hemiptera, Aphididae, Fordini). Each aphid species induces a characteristic gall on a single Pistacia host species. The genus Geoica (Fordini) induce similar spherical closed galls on the lower side of the leaflet's midvein, on different Pistacia species. Two species of Pistacia trees that harbor Geoica galls grow naturally in Israel: P. palaestina and P. atlantica. We analyzed the phylogeny and the genetic structure of the Geoica species complex in Israel, and assessed the genetic differentiation and the level of host plant specificity of the aphids between P. atlantica and P. palaestina. We found that the splitting of the genus between P. atlantica and P. palaestina is estimated to have occurred 24-25 Ma (the Oligocene/Miocene boundary). Five different haplotypes suggesting five different species have been further speciating among Geoica spp., galling on P. atlantica, and an additional three species, on P. palaestina.

Transcriptional up-regulation of host-specific terpene metabolism in aphid-induced galls of Pistacia palaestina.

Galling insects gain food and shelter by inducing specialized anatomical structures in their plant hosts. Such galls often accumulate plant defensive metabolites protecting the inhabiting insects from predation. We previously found that, despite a marked natural chemopolymorphism in natural populations of Pistacia palaestina, the monoterpene content in Baizongia pistaciae-induced galls is substantially higher than in leaves of their hosts. Here we show a general up-regulation of key structural genes in both the plastidial and cytosolic terpene biosynthetic pathways in galls as compared with non-colonized leaves. Novel prenyltransferases and terpene synthases were functionally expressed in Escherichia coli to reveal their biochemical function. Individual Pistacia trees exhibiting chemopolymorphism in terpene compositions displayed differential up-regulation of selected terpene synthase genes, and the metabolites generated by their gene products in vitro corresponded to the monoterpenes accumulated by each tree. Our results delineate molecular mechanisms responsible for the formation of enhanced monoterpene in galls and the observed intraspecific monoterpene chemodiversity displayed in P. palaestina. We demonstrate that gall-inhabiting aphids transcriptionally reprogram their host terpene pathways by up-regulating tree-specific genes, boosting the accumulation of plant defensive compounds for the protection of colonizing insects.

Standing on the shoulders of giants: young aphids piggyback on adults when searching for a host plant.

BACKGROUND: Upon the detection of imminent peril, pea aphids (Acyrthosiphon pisum) often drop off their host plant. Dropping in response to insect enemies is intermittent in nature, but when a mammalian herbivore feeds on their host plant, a large mixed-age group of aphids usually drops off the plant at once. Aphids that reach the ground are confronted with new, hostile environmental conditions and must therefore quickly walk toward a suitable host plant. The longer it takes an aphid to reach a host plant, the more it is exposed to the risks of starvation, desiccation and predation. RESULTS: We found that young nymphs, which have limited mobility and high mortality on the ground, quickly climb on conspecific (not necessarily parental) adults and cling to them before the latter start walking in search of a plant. This "riding" behavior is likely to be adaptive for the nymphs, for it shortens their journey and the time they spend off a host plant. Adults however, seem to be irritated by the riding nymphs, as they often actively try to remove them. CONCLUSIONS: After dropping from the host plant, young aphid nymphs travel at least part of the way back to a plant on the backs of adults. For the riding behavior to take place, nymphs need to successfully find adults and withstand removal attempts.

Direct consumptive interactions between mammalian herbivores and plant-dwelling invertebrates: prevalence, significance, and prospectus.

Mammalian herbivores induce changes in the chemical composition, phenology, distribution, and abundance of the plants they feed on. Consequently, invertebrate herbivores (predominantly insects) that depend on those plants, and the predators and parasitoids that are associated with them, may be affected. This plant-mediated indirect interaction between mammals and invertebrates has been extensively studied, but mammalian herbivores may also directly affect plant-dwelling invertebrates (PDI) by incidentally ingesting them while feeding. The ubiquity and small size of PDI render them highly susceptible to incidental ingestion, but as common as this interaction may intuitively seem, very little is known about its prevalence and ecological consequences. Nevertheless, cases of incidental ingestion of PDI and associated adaptations for avoiding it that have been sporadically documented in several invertebrate groups and life stages allow us to carefully extrapolate and conclude that it should be common in nature. Incidental ingestion may, therefore, bear significant consequences for PDI, but it may also affect the mammalian herbivores and the shared plants. Future research on incidental ingestion of PDI would have to overcome several technical difficulties to gain better insight into this understudied ecological interaction.

Differences in Monoterpene Biosynthesis and Accumulation in Pistacia palaestina Leaves and Aphid-Induced Galls.

Certain insect species can induce gall formation on numerous plants species. Although the mechanism of gall development is largely unknown, it is clear that insects manipulate their hosts' anatomy, physiology, and chemistry for their own benefit. It is well known that insect-induced galls often contain vast amounts of plant defensive compounds as compared to non-colonized tissues, but it is not clear if defensive compounds can be produced in situ in the galled tissues. To answer this question, we analyzed terpene accumulation patterns and possible independent biosynthetic potential of galls induced by the aphid Baizongia pistaciae L. on the terminal buds of Pistacia palaestina Boiss. We compared monoterpene levels and monoterpene synthase enzyme activity in galls and healthy leaves from individual trees growing in a natural setting. At all developmental stages, monoterpene content and monoterpene synthase activity were consistently (up to 10 fold on a fresh weight basis) higher in galls than in intact non-colonized leaves. A remarkable tree to tree variation in the products produced in vitro from the substrate geranyl diphosphate by soluble protein extracts derived from individual trees was observed. Furthermore, galls and leaves from the same trees displayed enhanced and often distinct biosynthetic capabilities. Our results clearly indicate that galls possess independent metabolic capacities to produce and accumulate monoterpenes as compared to leaves. Our study indicates that galling aphids manipulate the enzymatic machinery of their host plant, intensifying their own defenses against natural enemies.

Bevacizumab plus paclitaxel versus bevacizumab plus capecitabine as first-line treatment for HER2-negative metastatic breast cancer (TURANDOT): primary endpoint results of a randomised, open-label, non-inferiority, phase 3 trial.

BACKGROUND: The randomised phase 3 TURANDOT trial compared two approved bevacizumab-containing regimens for HER2-negative metastatic breast cancer in terms of efficacy, safety, and quality of life. The interim analysis did not confirm non-inferior overall survival (stratified hazard ratio [HR] 1·04; 97·5% repeated CI [RCI] -∞ to 1·69). Here we report final results of our study aiming to show non-inferior overall survival with first-line bevacizumab plus capecitabine versus bevacizumab plus paclitaxel for locally recurrent or metastatic breast cancer. METHODS: In this multinational, open-label, randomised phase 3 TURANDOT trial, patients aged 18 years or older who had an Eastern Cooperative Oncology Group performance status 0-2 and measurable or non-measurable HER2-negative locally recurrent or metastatic breast cancer who had received no previous chemotherapy for locally recurrent or metastatic breast cancer were stratified and randomly assigned (1:1) using permuted blocks of size six to either bevacizumab plus paclitaxel (bevacizumab 10 mg/kg on days 1 and 15 plus paclitaxel 90 mg/m(2) on days 1, 8, and 15 every 4 weeks) or bevacizumab plus capecitabine (bevacizumab 15 mg/kg on day 1 plus capecitabine 1000 mg/m(2) twice daily on days 1-14 every 3 weeks) until disease progression, unacceptable toxicity, or withdrawal of consent. Stratification factors were oestrogen or progesterone receptor status, country, and menopausal status. The primary objective was to show non-inferior overall survival with bevacizumab plus capecitabine versus bevacizumab plus paclitaxel in the per-protocol population by rejecting the null hypothesis of inferiority (HR ≥1·33) using a stratified Cox proportional hazard model. This trial is registered with ClinicalTrials.gov, number NCT00600340. FINDINGS: Between Sept 10, 2008, and Aug 30, 2010, 564 patients were randomised, representing the intent-to-treat population. The per-protocol population comprised 531 patients (266 in the bevacizumab plus paclitaxel group and 265 in the bevacizumab plus capecitabine group). At the final overall survival analysis after 183 deaths (69%) in 266 patients receiving bevacizumab plus paclitaxel and 201 (76%) in 265 receiving bevacizumab plus capecitabine in the per-protocol population, median overall survival was 30·2 months (95% CI 25·6-32·6 months) versus 26·1 months (22·3-29·0), respectively. The stratified HR was 1·02 (97·5% RCI -∞ to 1·26; repeated p=0·0070), indicating non-inferiority. The unstratified Cox model (HR 1·13 [97·5% RCI -∞ to 1·39]; repeated p=0·061) did not support the primary analysis. Intent-to-treat analyses were consistent with the per-protocol results. The most common grade 3 or worse adverse events were neutropenia (54 [19%] of 284 patients in the bevacizumab plus paclitaxel group vs 5 [2%] of 277 patients in the bevacizumab plus capecitabine group), hand-foot syndrome (1 [<1%] vs 43 [16%]), peripheral neuropathy (39 [14%] vs 1 [<1%]), leucopenia (20 [7%] vs 1 [<1%]), and hypertension (12 [4%] vs 16 [6%]). Serious adverse events were reported in 65 (23%) of 284 patients receiving bevacizumab plus paclitaxel and 68 (25%) of 277 receiving bevacizumab plus capecitabine. Deaths in two (1%) of 284 patients in the bevacizumab plus paclitaxel group were deemed by the investigator to be treatment-related. No treatment-related deaths occurred in the bevacizumab plus capecitabine group. INTERPRETATION: Bevacizumab plus capecitabine represents a valid first-line treatment option for HER2-negative locally recurrent or metastatic breast cancer, offering good tolerability without compromising overall survival compared with bevacizumab plus paclitaxel. Although progression-free survival with the bevacizumab plus capecitabine combination is inferior to that noted with bevacizumab plus paclitaxel, we suggest that physicians should consider possible predictive risk factors for overall survival, individual's treatment priorities, and the differing safety profiles. FUNDING: Roche.

Predictive role of hand-foot syndrome in patients receiving first-line capecitabine plus bevacizumab for HER2-negative metastatic breast cancer.

BACKGROUND: Correlations between development of hand-foot syndrome (HFS) and efficacy in patients receiving capecitabine (CAP)-containing therapy are reported in the literature. We explored the relationship between HFS and efficacy in patients receiving CAP plus bevacizumab (BEV) in the TURANDOT randomised phase III trial. METHODS: Patients with HER2-negative locally recurrent/metastatic breast cancer (LR/mBC) who had received no prior chemotherapy for LR/mBC were randomised to BEV plus paclitaxel or BEV-CAP until disease progression or unacceptable toxicity. This analysis included patients randomised to BEV-CAP who received ⩾1 CAP dose. Potential associations between HFS and both overall survival (OS; primary end point) and progression-free survival (PFS; secondary end point) were explored using Cox proportional hazards analyses with HFS as a time-dependent covariate (to avoid overestimating the effect of HFS on efficacy). Landmark analyses were also performed. RESULTS: Among 277 patients treated with BEV-CAP, 154 (56%) developed HFS. In multivariate analyses, risk of progression or death was reduced by 44% after the occurrence of HFS; risk of death was reduced by 56%. The magnitude of effect on OS increased with increasing HFS grade. In patients developing HFS within the first 3 months, median PFS from the 3-month landmark was 10.0 months vs 6.2 months in patients without HFS. Two-year OS rates were 63% and 44%, respectively. CONCLUSIONS: This exploratory analysis indicates that HFS occurrence is a strong predictor of prolonged PFS and OS in patients receiving BEV-CAP for LR/mBC. Early appearance of HFS may help motivate patients to continue therapy.

Long-term effects of continuing adjuvant tamoxifen to 10 years versus stopping at 5 years after diagnosis of oestrogen receptor-positive breast cancer: ATLAS, a randomised trial.

BACKGROUND: For women with oestrogen receptor (ER)-positive early breast cancer, treatment with tamoxifen for 5 years substantially reduces the breast cancer mortality rate throughout the first 15 years after diagnosis. We aimed to assess the further effects of continuing tamoxifen to 10 years instead of stopping at 5 years. METHODS: In the worldwide Adjuvant Tamoxifen: Longer Against Shorter (ATLAS) trial, 12,894 women with early breast cancer who had completed 5 years of treatment with tamoxifen were randomly allocated to continue tamoxifen to 10 years or stop at 5 years (open control). Allocation (1:1) was by central computer, using minimisation. After entry (between 1996 and 2005), yearly follow-up forms recorded any recurrence, second cancer, hospital admission, or death. We report effects on breast cancer outcomes among the 6846 women with ER-positive disease, and side-effects among all women (with positive, negative, or unknown ER status). Long-term follow-up still continues. This study is registered, number ISRCTN19652633. FINDINGS: Among women with ER-positive disease, allocation to continue tamoxifen reduced the risk of breast cancer recurrence (617 recurrences in 3428 women allocated to continue vs 711 in 3418 controls, p=0·002), reduced breast cancer mortality (331 deaths vs 397 deaths, p=0·01), and reduced overall mortality (639 deaths vs 722 deaths, p=0·01). The reductions in adverse breast cancer outcomes appeared to be less extreme before than after year 10 (recurrence rate ratio [RR] 0·90 [95% CI 0·79­1·02] during years 5­9 and 0·75 [0·62­0·90] in later years; breast cancer mortality RR 0·97 [0·79­1·18] during years 5­9 and 0·71 [0·58­0·88] in later years). The cumulative risk of recurrence during years 5­14 was 21·4% for women allocated to continue versus 25·1% for controls; breast cancer mortality during years 5­14 was 12·2% for women allocated to continue versus 15·0% for controls (absolute mortality reduction 2·8%). Treatment allocation seemed to have no effect on breast cancer outcome among 1248 women with ER-negative disease, and an intermediate effect among 4800 women with unknown ER status. Among all 12,894 women, mortality without recurrence from causes other than breast cancer was little affected (691 deaths without recurrence in 6454 women allocated to continue versus 679 deaths in 6440 controls; RR 0·99 [0·89­1·10]; p=0·84). For the incidence (hospitalisation or death) rates of specific diseases, RRs were as follows: pulmonary embolus 1·87 (95% CI 1·13­3·07, p=0·01 [including 0·2% mortality in both treatment groups]), stroke 1·06 (0·83­1·36), ischaemic heart disease 0·76 (0·60­0·95, p=0·02), and endometrial cancer 1·74 (1·30­2·34, p=0·0002). The cumulative risk of endometrial cancer during years 5­14 was 3·1% (mortality 0·4%) for women allocated to continue versus 1·6% (mortality 0·2%) for controls (absolute mortality increase 0·2%). INTERPRETATION: For women with ER-positive disease, continuing tamoxifen to 10 years rather than stopping at 5 years produces a further reduction in recurrence and mortality, particularly after year 10. These results, taken together with results from previous trials of 5 years of tamoxifen treatment versus none, suggest that 10 years of tamoxifen treatment can approximately halve breast cancer mortality during the second decade after diagnosis. FUNDING: Cancer Research UK, UK Medical Research Council, AstraZeneca UK, US Army, EU-Biomed.

Weekly carboplatin with paclitaxel compared to standard three-weekly treatment in advanced epithelial ovarian carcinoma--a retrospective study.

OBJECTIVE: To retrospectively compare primary treatment with weekly carboplatin/paclitaxel (PC-W) to the standard 3-weekly carboplatin/paclitaxel (PC-3 W) in women with advanced epithelial ovarian cancer, tubal carcinoma and primary peritoneal carcinoma. METHODS: Medical records were assessed for age, stage of disease, tumor histology and grade, BRCA mutation status, and platinum sensitivity. Patients were treated with either paclitaxel (175 mg/m(2)) and carboplatin (AUC 6) every three weeks (PC-3 W; 133 patients), or with weekly paclitaxel (80 mg/m(2)) and weekly carboplatin (AUC 2) on days 1, 8, and 15 every 28 days (PC-W; 267 patients). RESULTS: Patient baseline characteristics were similar in both groups. Median overall survival (OS) was similar for PC-W and PC-3 W (64.5 months vs. 61.5 months), but PC-W had longer median progression-free survival [PFS: 27.4 months (95% CI, 22.7-31.4) vs. 19.5 months (95% CI, 15.6-22.2) for PC-3 W, p = 0.0024] and a longer median platinum-free interval [PFI: 22.1 months (95% CI, 16.0-24.5) vs. 14.2 months (95% CI, 10.7-17.2) for PC-3 W, p = 0.0075]. PC-W showed a significantly higher response rate (86.4% vs. 77.9% for PC-3 W, p = 0.0435). Multivariate analysis including for age at diagnosis, stage of disease, optimal debulking, histology, BRCA status, pretreatment CA-125 and PFI revealed that the PC-W women had lower risk of death (HR = 0.587, 95% CI, 0.402-0.857, p = 0.0058), lower risk of disease progression (HR = 0.494, 95% CI, 0.359-0.680, p < 0.0001), higher 2- and 3-year survival rates, and decreased grade II hair loss, neuropathy and thrombocytopenia compared with the PC-3 W women. CONCLUSION: The PC-W protocol improved PFS and had a similar OS as PC-3W.

The stimuli evoking the aerial-righting posture of falling pea aphids.

Some wingless insects possess aerial righting reflexes, suggesting that adaptation for controlling body orientation while falling through air could have preceded flight. When threatened by natural enemies, wingless pea aphids (Acyrthosiphon pisum) may drop off their host plant and assume a stereotypic posture that rotates them in midair to land on their feet. The sensory information triggering aphids to assume this posture has so far been unknown. We subjected aphids to a series of tests, isolating the sensory cues experienced during free-fall. Falling aphids assumed the righting posture and landed upright irrespective of whether the experiments were carried out in the light or in complete darkness. Detachment of the tarsi from the substrate triggered the aphids to assume the posture rapidly, but only for a brief period. Rotation (mainly roll and yaw) of the body in air, in the light, caused aphids to assume the posture and remain in it throughout rotation. In contrast, aphids rotated in the dark did not respond. Acceleration associated with falling or airflow over the body per se did not trigger the posture. However, sensing motion relative to air heightened the aphids' responsiveness to rotation in the light. These results suggest that the righting posture of aphids is triggered by a tarsal reflex, but, once the aphid is airborne, vision and a sense of motion relative to air can augment the response. Hence, aerial righting in a wingless insect could have emerged as a basic tarsal response and developed further to include secondary sensory cues typical of falling.

The combination of gemcitabine and carboplatin shows similar efficacy in the treatment of platinum-resistant and platinum-sensitive recurrent epithelial ovarian cancer patients.

The aim of this study was to evaluate progression-free survival, overall survival (OS), response rate (RR), and clinical benefit in recurrent ovarian cancer patients treated with gemcitabine and carboplatin and to compare the outcome among platinum-resistant and platinum-sensitive patients. A retrospective study using the medical records of patients diagnosed and treated for recurrent epithelial ovarian cancer, fallopian tube carcinoma, or primary peritoneal carcinoma with gemcitabine and carboplatin from 2005 through 2012 at the Tel Aviv Sourasky Medical Center. The treatment regimen was carboplatin (area under the curve=5) administered on day 1 and gemcitabine 850 mg/m administered on days 1 and 8 in a 21-day cycle. Seventy patients with a median age of 57 years (range: 38-86) were included in the study. Most patients (94.3%) were initially diagnosed with stage III-IV disease and 44.3% had platinum-sensitive disease. Median progression-free survival in platinum-sensitive patients was 6.3 months [95% confidence interval (CI): 4.3-8.3] and 6.3 months (95% CI: 4.6-7.9) in platinum-resistant patients. Median overall survival was 15.8 months (95% CI: 13.6-18.1) in the platinum-sensitive patients and 18.4 months (95% CI: 10.0-27.8) in the platinum-resistant patients. Platinum-sensitive patients had a RR of 43.2% and platinum-resistant patients had a RR of 39.1%. The clinical benefit was 70.5% in platinum-sensitive patients and 65.2% in platinum-resistant patients. Overall treatment had a favorable safety profile. Gemcitabine and carboplatin demonstrate moderate toxicity with similar efficacy in both platinum-sensitive and platinum-resistant epithelial ovarian cancer, suggesting reversal of platinum resistance by gemcitabine.

Should a loop ileostomy closure in rectal cancer patients be done during or after adjuvant chemotherapy?

BACKGROUND AND OBJECTIVE: The influence of ileostomy closure timing on surgical and oncologic outcome was investigated in patients with locally advanced rectal cancer receiving adjuvant chemotherapy after low anterior resection. METHODS: Consecutive patients diagnosed with T3-4/N+ rectal cancer, treated by neoadjuvant chemoradiation and low anterior resection during 2000-2012 were retrospectively evaluated. Patients undergoing closure during adjuvant chemotherapy (Group A) were compared to patients undergoing closure after completing chemotherapy (Group B). RESULTS: A total of the 165 patients met inclusion criteria, of whom 104 received adjuvant chemotherapy (25 in Group A and 79 in Group B). The pathologic stage was higher in Group B (P = 0.015). The rates of postoperative complications were similar (16% for Group A and 15% for Group B, P = 0.88), as was hospital stay (mean 5.78 days for Group A and 6.25 days for Group B, P = 0.7). There was no significant difference in recurrence rate and overall survival between the groups. CONCLUSIONS: Referral to ileostomy closure in relation to adjuvant chemotherapy is influenced by pathologic stage. Early referral appears to be reserved to a small number of patients with lower pathologic stage. Timing of ileostomy closure does not change short- or long-term results.

Cytoreduction surgery with hyperthermic intraperitoneal chemotherapy in recurrent ovarian cancer improves progression-free survival, especially in BRCA-positive patients- a case-control study.

BACKGROUND: Approximately 70% of women diagnosed with advanced-stage ovarian cancer experience disease recurrence. Survival data were compared between a group of recurrent epithelial ovarian cancer (rEOC) patients treated by cytoreduction and hyperthermic intraperitoneal chemotherapy (HIPEC) and a matched group of rEOC patients treated by systemic chemotherapy only (without surgery). Treatment outcome in relation to the patients' BRCA status was compared. METHODS: Twenty-seven rEOC patients treated by cytoreduction and HIPEC were selected from our database and matched (1:3) with 84 rEOC patients treated with chemotherapy only. Progression-free survival (PFS) and overall survival (OS) in the two groups were analyzed and compared. RESULTS: The estimated median PFS was 15 months in the HIPEC group and 6 months in the systemic chemotherapy group (P = 0.001). The median OS following HIPEC treatment has not been reached, since more than 70% of the women were alive at the time of analysis. The 5-year survival rate was significantly higher in the HIPEC treated patients compared to that of the controls (79% vs. 45%, P = 0.016). BRCA status did not affect PFS. CONCLUSIONS: HIPEC after surgical cytoreduction in patients with rEOC appears beneficial compared to systemic chemotherapy treatment alone. The benefit is even greater in BRCA mutation carriers.

The mono - and sesquiterpene content of aphid-induced galls on Pistacia palaestina is not a simple reflection of their composition in intact leaves.

Pistacia palaestina Boiss. (Anacardiaceae), a sibling species of P. terebinthus also known as turpentine tree or terebinth tree, is common in the Levant region. The aphid Baizongia pistaciae L. manipulates the leaves of the plant to form large galls, which provide both food and protection for its developing offspring. We analyzed the levels and composition of mono-and sesquiterpenes in both leaves and galls of ten naturally growing trees. Our results show that monoterpene hydrocarbons are the main constituents of P. palaestina leaves and galls, but terpene levels and composition vary among trees. Despite this inter-tree variation, terpene levels and compositions in galls from different trees resemble each other more than the patterns displayed by leaves from the same trees. Generally, galls contain 10 to 60 fold higher total terpene amounts than leaves, especially of the monoterpenes α-pinene and limonene. Conversely, the leaves generally accumulate more sesquiterpenes, in particular E-caryophyllene, germacrene D and δ-cadinene, in comparison to galls. Our results clearly show that the terpene pattern in the galls is not a simple reflection of that of the leaves and suggest that aphids have a strong impact on the metabolism of their host plant, possibly for their own defense.

The role of onion-associated fungi in bulb mite infestation and damage to onion seedlings.

In Israel Rhizoglyphus robini is considered to be a pest in its own right, even though the mite is usually found in association with fungal pathogens. Plant protection recommendations are therefore to treat germinating onions seedlings, clearly a crucial phase in crop production, when mites are discovered. The aim of this study was to determine the role of fungi in bulb mite infestation and damage to germinating onion seedlings. Accordingly we (1) evaluated the effect of the mite on onion seedling germination and survival without fungi, (2) compared the attraction of the mite to species and isolates of various fungi, (3) assessed the effect of a relatively non-pathogenic isolate of Fusarium oxysporum on mite fecundity, and (4) determined the effects of the mite and of F. oxysporum separately and together, on onion seedling germination and sprout development. A significant reduction of seedling survival was recorded only in the 1,000 mites/pot treatment, after 4 weeks. Mites were attracted to 6 out of 7 collected fungi isolates. Mite fecundity on onion sprouts infested with F. oxysporum was higher than on non-infested sprouts. Survival of seedlings was affected by mites, fungi, and their combination. Sprouts on Petri dishes after 5 days were significantly longer in the control and mite treatments than both fungi treatments. During the 5-day experiment more mites were always found on the fungi-infected sprouts than on the non-infected sprouts. Future research using suppressive soils to suppress soil pathogens and subsequent mite damage is proposed.

Gall volatiles defend aphids against a browsing mammal.

BACKGROUND: Plants have evolved an astonishing array of survival strategies. To defend against insects, for example, damaged plants emit volatile organic compounds that attract the herbivore's natural enemies. So far, plant volatile responses have been studied extensively in conjunction with leaf chewing and sap sucking insects, yet little is known about the relationship between plant volatiles and gall-inducers, the most sophisticated herbivores. Here we describe a new role for volatiles as gall-insects were found to benefit from this plant defence. RESULTS: Chemical analyses of galls triggered by the gregarious aphid Slavum wertheimae on wild pistachio trees showed that these structures contained and emitted considerably higher quantities of plant terpenes than neighbouring leaves and fruits. Behavioural assays using goats as a generalist herbivore confirmed that the accumulated terpenes acted as olfactory signals and feeding deterrents, thus enabling the gall-inducers to escape from inadvertent predation by mammals. CONCLUSIONS: Increased emission of plant volatiles in response to insect activity is commonly looked upon as a "cry for help" by the plant to attract the insect's natural enemies. In contrast, we show that such volatiles can serve as a first line of insect defences that extends the 'extended phenotype' represented by galls, beyond physical boundaries. Our data support the Enemy hypothesis insofar that high levels of gall secondary metabolites confer protection against natural enemies.

Horizontal transmission of the insect symbiont Rickettsia is plant-mediated.

Bacteria in the genus Rickettsia, best known as vertebrate pathogens vectored by blood-feeding arthropods, can also be found in phytophagous insects. The presence of closely related bacterial symbionts in evolutionarily distant arthropod hosts presupposes a means of horizontal transmission, but no mechanism for this transmission has been described. Using a combination of experiments with live insects, molecular analyses and microscopy, we found that Rickettsia were transferred from an insect host (the whitefly Bemisia tabaci) to a plant, moved inside the phloem, and could be acquired by other whiteflies. In one experiment, Rickettsia was transferred from the whitefly host to leaves of cotton, basil and black nightshade, where the bacteria were restricted to the phloem cells of the plant. In another experiment, Rickettsia-free adult whiteflies, physically segregated but sharing a cotton leaf with Rickettsia-plus individuals, acquired the Rickettsia at a high rate. Plants can serve as a reservoir for horizontal transmission of Rickettsia, a mechanism which may explain the occurrence of phylogenetically similar symbionts among unrelated phytophagous insect species. This plant-mediated transmission route may also exist in other insect-symbiont systems and, since symbionts may play a critical role in the ecology and evolution of their hosts, serve as an immediate and powerful tool for accelerated evolution.

Plant-feeding and non-plant feeding phytoseiids: differences in behavior and cheliceral morphology.

In previous studies plant feeding behavior of plant- and non-plant feeding phytoseiids was never examined directly. Moreover, in these studies the cheliceral morphology of phytoseiids was not associated with their ability to feed on plants. In the present study, we monitored the plant-feeding behavior of Euseius scutalis and Amblyseius swirskii. Only E. scutalis was observed penetrating the leaf surface with the movable digit and feeding. Second, using a dye and coloring the gut as an indicator for feeding, we found that E. scutalis pierced an artificial membrane and fed whereas A. swirskii did not. Finally, to identify morphological characteristics typical of plant feeders versus non-plant feeders, we used scanning electron microscopy to examine the adaxial (inner) profile of the chelicerae in 13 phytoseiid species. The only parameter that distinguished between plant- and non-plant feeders was the ratio of the dorsal perimeter length of the fixed digit to the ventral perimeter length of the movable digit. Plant-feeders were characterized by ratio values greater than one whereas the values for non plant-feeders were lower than one. We suggest that a shorter and less curved movable digit, expressed by a high ratio, will facilitate the penetration of the leaf surface. Cheliceral traits proposed here as typical of plant feeders, were observed for five genera, indicating that plant-feeding may be more common in the Phytoseiidae than previously reported. We propose that the ability to feed on plants be added as a cross type trait of phytoseiid life-style types.

Revealing cryptic interactions between large mammalian herbivores and plant-dwelling arthropods via DNA metabarcoding.

In the past decade, it has become clear that omnivory, feeding on more than one trophic level, is important in natural and agricultural systems. Large mammalian herbivores (LMH) frequently encounter plant-dwelling arthropods (PDA) on their food plants. Yet, ingestion of PDA by LMH is only rarely addressed and the extent of this direct trophic interaction, especially at the PDA community level, remains unknown. Using a DNA-metabarcoding analysis on feces of free-ranging cattle from a replicated field experiment of heavily and moderately grazed paddocks, we reveal that feeding cattle (incidentally) ingest an entire food chain of PDA including herbivores, predators and parasites. Overall, 25 families of insects and four families of arachnids were ingested, a pattern that varied over the season, but not with grazing intensity. We identified the functional groups of PDA vulnerable to ingestion, such as sessile species and immature life stages. Most of the fecal samples (76%) contained sequences belonging to PDA, indicating that direct interactions are frequent. This study highlights the complex trophic connections between LMH and PDA. It may even be appropriate to consider LMH as omnivorous enemies of PDA.