Discovery of Three Bemisia tabaci Effectors and Their Effect on Gene Expression in Planta

Bemisia tabaci (whitefly) is a polyphagous agroeconomic pest species complex. Two members of this species complex, Mediterranean (MED) and Middle-East-Asia Minor 1 (MEAM1), have a worldwide distribution and have been shown to manipulate plant defenses through effectors. In this study, we used three different strategies to identify three MEAM1 proteins that can act as effectors. Effector B1 was identified using a bioinformatics-driven effector-mining strategy, whereas effectors S1 and P1 were identified in the saliva of whiteflies collected from artificial diet and in phloem exudate of tomato on which nymphs were feeding, respectively. These three effectors were B. tabaci specific and able to increase whitefly fecundity when transiently expressed in tobacco plants (Nicotiana tabacum). Moreover, they reduced growth of Pseudomonas syringae pv. tabaci in Nicotiana benthamiana. All three effectors changed gene expression in planta, and B1 and S1 also changed phytohormone levels. Gene ontology and KEGG pathway enrichment analysis pinpointed plant-pathogen interaction and photosynthesis as the main enriched pathways for all three effectors. Our data thus show the discovery and validation of three new B. tabaci MEAM1 effectors that increase whitefly fecundity and modulate plant immunity. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

P–684 Impact of GnRH antagonist pretreatment on oocyte yield after ovarian stimulation: a retrospective analysis

Study question

Does a 3-day pretreatment course with a GnRH antagonist in the early follicular phase increase the number of oocytes in a GnRH antagonist stimulation protocol?

Summary answer

The administration of 3 days of GnRH antagonist before starting ovarian stimulation in a GnRH antagonist protocol increases the number of COCs (Cumulus-Oocyte-Complexes).

What is known already

The GnRH antagonist protocol is characterized by higher gonadotropin and E2 serum levels at the start of ovarian stimulation (OS), compared with a long pituitary down regulation protocol. The unsuppressed FSH level at the start of a GnRH antagonist cycle allows the initial growth of follicles before addition of exogenous FSH, which may result in asynchrony of the follicular cohort. Menstrual administration of a GnRH antagonist can inhibit follicle growth and improve homogeneity of recruitable follicles. Previous studies showed a trend toward higher numbers of COCs and improved maturation and fertilization rates of retrieved oocytes.

Study design, size, duration

Retrospective single center crossover study, including consecutive women enrolled in an IVF program in a university hospital from January 2011 to December 2020. All women underwent one standard GnRH antagonist stimulation cycle (“standard cycle”) and one GnRH antagonist stimulation cycle preceded by early administration of GnRH antagonist for 3 days (“pretreatment cycle”). Women with basal progesterone levels >1.5ng/ml, and women undergoing oocyte freezing, oocyte donation or PGT were excluded. In total, 427 patients were included.

Participants/materials, setting, methods

Women were included when the pretreatment cycle occurred within a time interval of < 12 months following the start of stimulation in the standard cycle. The primary outcome was the total number of COCs.

Main results and the role of chance

The average female age was 35.1 ± 4.7 years. Indications for fertility treatment included unexplained infertility (34.3%), male-factor infertility (33.3%), age (16.9%), PCOS (8.2%) and endometriosis (2.6%). All cycles were divided into two groups: group 1 (standard, 427 cycles) and group 2 (pretreatment, 427 cycles). The mean duration of stimulation was similar in both groups (10.3 vs 10.3 days, p = 0.2). The starting dose of gonadotropin (196.8 vs 234.9IU, p < 0.001) and total amount of gonadotropin used (2000.7 vs 2415.2IU, p < 0.001) were higher in group 2. The total number of obtained COCs (6.2 vs 8.8 p < 0.001) and the number of mature oocytes (4.2 vs 6.4 p < 0.001) were significantly higher in group 2. The Generalized estimating equation (GEE) multivariate regression analysis showed that the pretreatment strategy had a significant positive effect on the number of COCs (coefficient 2.8, p value <0.001 after adjusting for the confounders age, indication of infertility, stimulation dose, type and total amount of gonatropins used).

Limitations, reasons for caution

Despite the large dataset, the presence of biases related to the retrospective study design cannot be excluded. Besides, the impact of GnRH pretreatment on pregnancy rate cannot be assessed because of the crossover design.

Wider implications of the findings: A 3-day course of GnRH antagonist pretreatment increases the number of COCs obtained after OS. Furthermore, since the initiation of OS in a GnRH antagonist protocol relies on the occurrence of spontaneous menses, addition of three days of GnRH antagonist pretreatment may enhance scheduling flexibility without reducing efficacy.

Trial registration number

Not applicable

P–318 Short (seven days) versus conventional (fourteen days) estrogen priming in an artificial frozen embryo transfer cycle: a randomised controlled trial

Study question

What is the impact of seven days versus fourteen days’ estrogen (E2) priming on the clinical outcome of frozen-embryo-transfer in artificially prepared endometrium (FET-HRT) cycles?

Summary answer

No significant difference in clinical/ongoing pregnancy rate was observed when comparing 7 versus 14 days of estrogen priming before starting progesterone (P) supplementation.

What is known already

One (effective) method for endometrial preparation prior to frozen embryo transfer is hormone replacement therapy (HRT), a sequential regimen with E2 and P, which aims to mimic the endocrine exposure of the endometrium in a physiological cycle. The average duration of E2 supplementation is generally 12–14 days, however, this protocol has been arbitrarily chosen whereas, the optimal duration of E2 implementation remains unknown.

Study design, size, duration

This is a single-center, randomized, controlled, open-label pilot study. All FET-HRT cycles were performed in a tertiary centre between October 2018 and December 2020. Overall, 150 patients were randomized of whom 132 were included in the analysis after screening failure and drop-out.

Participants/materials, setting, methods

The included patients were randomized into one of 2 groups; group A (7 days of E2 prior to P supplementation) and group B (14 days of E2 prior to P supplementation). Both groups received blastocyst stage embryos for transfer on the 6th day of vaginal P administration. Pregnancy was assessed by an hCG blood test 12 days after FET and clinical pregnancy was confirmed by transvaginal ultrasound at 7 weeks of gestation.

Main results and the role of chance

Following the exclusion of drop-outs and screening failures, 132 patients were finally included both in group A (69 patients) or group B (63 patients). Demographic characteristics for both groups were comparable. The positive pregnancy rate was 46.4% and 53.9%, (p 0.462) for group A and group B, respectively. With regard to the clinical pregnancy rate at 7 weeks, no statistically significant difference was observed (36.2% vs 36.5% for group A and group B, respectively, p = 0.499). The secondary outcomes of the study (biochemical pregnancy, miscarriage and live birth rate) were also comparable between the two arms for both PP and ITT analysis. Multivariable logistic regression showed that the HRT scheme is not associated with pregnancy rate, however, the P value on the day of ET is significantly associated with the pregnancy outcome.

Limitations, reasons for caution

This study was designed as a proof of principle trial with a limited study population and therefore underpowered to determine the superiority of one intervention over another. Instead, the purpose of the present study was to explore trends in outcome differences and to allow us to safely design larger RCTs.

Wider implications of the findings: The results of this study give the confidence to perform larger-scale RCTs to confirm whether a FET-HRT can be performed safely in a shorter time frame, thus, reducing the TTP, while maintaining comparable pregnancy and live birth rates.

Trial registration number

NCT03930706

P–462 First live birth after fertility preservation using vitrified oocytes in a woman with mosaic Turner syndrome

Study question

Is oocyte vitrification an option for preserving the fertility of women diagnosed with Turner syndrome (TS)?

Summary answer

We report the first live birth achieved using cryopreserved oocytes in a woman diagnosed with mosaic Turner syndrome.

What is known already

Women with TS are at extremely high risk for premature ovarian insufficiency (POI) and infertility. Although the desire of becoming parents may be fulfilled through egg donation or adoption, fertility preservation using ovarian tissue cryopreservation or oocyte vitrification has been offered to adolescents with TS before complete exhaustion of their follicular stockpile. However, women with TS exhibit higher rates of pregnancy loss and obstetric complications, and the feasibility of fertility preservation in TS is hampered by the reduced follicular pool and by concerns about the X chromosomal content of oocytes and follicular cells.

Study design, size, duration

Case report in a university hospital.

Participants/materials, setting, methods

A 25-year-old woman with Turner syndrome mosaicism (45,X0[14]/46,XX[86]) was referred for fertility preservation (FP) counseling. Serum antimüllerian hormone (AMH) level was normal (6.4 µg/L). In view of parenthood postponement and because of the unpredictable rate of follicle loss, the woman underwent two cycles of ovarian stimulation using recombinant follicle stimulating hormone (rFSH), 200–250 IU/day for 8 resp. 12 days, in a GnRH antagonist protocol.

Main results and the role of chance

In total, 29 metaphase II oocytes (MII) were vitrified. Five years later, the patient returned to the clinic with a desire for pregnancy. Because of evidence of considerable AMH decline (–56% in an interval of four years), the patient was advised to utilize her cryopreserved oocytes for in-vitro fertilization with preimplantation genetic testing for aneuploidy screening (PGT-A). All 29 MII oocytes were thawed; 26 oocytes survived (89.7%) and were inseminated using intracytoplasmic sperm injection (ICSI). Thirteen oocytes were fertilized normally. Three good quality blastocysts ensued and were vitrified after trophectoderm biopsy for PGT-A using array-CGH. Two blastocysts were found euploid. One was thawed and transferred into the uterus using a HRT priming protocol. An uneventful pregnancy occurred. The patient delivered a healthy baby girl weighing 3490 g at 40 weeks of gestation.

Limitations, reasons for caution

Cryopreservation of oocytes and/or ovarian tissue in selected postmenarchal girls or young women with Turner syndrome is an investigational FP approach that may result in genetic parenthood. The feasibility of FP in TS individuals is limited to those with evidence of ovarian function, before POI occurs.

Wider implications of the findings: Cryopreservation of mature oocytes after ovarian stimulation is a realistic option for FP in selected postmenarchal individuals with mosaic TS. Whether PGT-A may reduce the risk of pregnancy loss in TS has to be confirmed by further studies.

Trial registration number

Not applicable

P–464 What is the optimal ovarian stimulation (OS) protocol for women who undergo planned oocyte cryopreservation (POC)?

Study question

When repeated cycles of OS for planned oocyte cryopreservation using a standard GnRH antagonist protocol are required, can OS protocol modifications improve oocyte yield?

Summary answer

Compared to repeating a standard GnRH antagonist protocol, switching to a long GnRH agonist protocol for POC results in a higher number of cryopreserved oocytes.

What is known already

The total number of cryopreserved oocytes is a key parameter of POC programs because of its association with livebirth. A substantial proportion of women embarking on POC will undergo repeated cycles of OS to reach their desired target number of vitrified oocytes. According to recent guidelines, the GnRH antagonist protocol with GnRH agonist triggering is considered the first choice protocol for POC, because of its safety profile and convenience. However, in women with normal ovarian reserve, the long GnRH agonist protocol results in a higher number of oocytes retrieved. Evidence regarding the optimal protocol for POC is limited.

Study design, size, duration

This is a single-centre, retrospective cohort study including 283 women who had a first cycle for POC using a standard GnRH antagonist protocol and who requested a second OS cycle to increase their total number of vitrified oocytes for later use. The choice of protocol for the second cycle was left at the discretion of the reproductive medicine specialist. All OS cycles took place between January 2009 and December 2019 in a tertiary referral hospital.

Participants/materials, setting, methods

After ovarian reserve testing, the first cycle OS was performed using rFSH or HPhMG in a GnRH antagonist protocol. For the second cycle, a GnRH antagonist protocol with or without antagonist pretreatment, or a long GnRH agonist protocol was prescribed. The primary outcome was the number of mature oocytes (MII) vitrified per cycle. Cycle characteristics were compared. Data were assessed by generalized estimating equation (GEE) regression analysis adjusting for covariates.

Main results and the role of chance

In total, 226 (79.9%) women had a GnRH antagonist protocol and 57 (20.1%) had a long GnRH agonist protocol in their second OS cycle for POC. Overall, mean age was 36.6±2.4 years. The median (CI) number of mature oocytes vitrified after the second OS cycle was significantly higher than that after the first cycle [8 (5–11) vs. 7 (4–10), p < 0.001]. According to GEE multivariate regression, adjusting for relevant confounders, switching from a GnRH antagonist protocol in the first cycle to a long GnRH agonist protocol in the second cycle was the only significant predictor of the number of vitrified oocytes after the subsequent cycle (coefficient 1.59, CI 0.29–2.89, p-value = 0.017). Age, AFC, initial dose and type of gonadotropins did not predict the number of vitrified oocytes. None of the women developed moderate or severe OHSS.

Similarly, of 174 women who underwent their first OS cycle with a standard GnRH antagonist protocol, 133 women (76.4%) had the same protocol for their second cycle and 41 women (23.6%) an additional three-day course of GnRH antagonist pretreatment. According to GEE multivariate regression, this protocol modification did not result in more mature oocytes available for vitrification (coefficient –0.25, CI –1.86–1.36, p-value = 0.76).

Limitations, reasons for caution

These data should be interpreted with caution because of the retrospective design and limited sample. Although more oocytes were obtained with a long GnRH agonist protocol we have no data on livebirth in women returning to use their oocytes to support the choice for a specific OS protocol for POC.

Wider implications of the findings: Although oocyte yield in the context of POC is an important parameter that may be modulated by the choice of OS protocol, the ultimate outcome measure of a successful POC program is livebirth after oocyte vitrification. Future research of oocyte parameters reflecting oocyte quality is paramount.

Trial registration number

Not applicable

Combining QTL mapping with transcriptome and metabolome profiling reveals a possible role for ABA signaling in resistance against the cabbage whitefly in cabbage

Whiteflies are among the world's most significant agricultural pests and chemical insecticides are extensively used to reduce crop damage to acceptable levels. However, nearly all insecticides pose a threat to the environment and alternative control methods, such as breeding of crop varieties that are inherently insect-resistant, are needed. Previously, a strong source of plant-age dependent resistance to the cabbage whitefly (Aleyrodes proletella) has been identified in the modern white cabbage (Brassica oleracea var. capitata) variety Rivera. However, nothing is known about the molecular mechanisms or the genes involved in this resistance. In the present study, a multidisciplinary approach combining transcriptome and metabolome profiling with genetic mapping was used to identify the molecular players of whitefly resistance in cabbage. Transcriptome profiles of young (susceptible) and older (resistant) Rivera plants were analyzed using RNA sequencing. While many genes involved in general processes were differentially expressed between both ages, several defense-related processes were overrepresented in the transcriptome profile of older plants. Hormone measurements revealed that jasmonic acid (JA) levels decreased upon whitefly infestation at both plant ages. Interestingly, abscisic acid (ABA) levels showed contrasting effects in response to whitefly infestation: ABA levels were reduced in young plants but induced in older plants upon whitefly feeding. Auxin levels were significantly lower in older plants compared with young plants, independent of whitefly presence, while glucosinolate levels were higher. Additionally, whitefly performance was monitored in an F2 population derived from a cross between Rivera and the susceptible white cabbage variety Christmas Drumhead. Significant QTL intervals were mapped on chromosome 2 and 9 for oviposition rate and whitefly adult survival, respectively. Several genes that were higher expressed in older plants and located in the identified QTL intervals were orthologous to Arabidopsis genes that have been related to ABA signaling, suggesting a role for ABA in the regulation of resistance towards whiteflies. Our results show that combining different omics approaches is a useful strategy to identify candidate genes underlying insect resistance.

Identification of a drimenol synthase and drimenol oxidase from Persicaria hydropiper, involved in the biosynthesis of insect deterrent drimanes

The sesquiterpenoid polygodial, which belongs to the drimane family, has been shown to be an antifeedant for a number of herbivorous insects. It is presumed to be synthesized from farnesyl diphosphate via drimenol, subsequent C-12 hydroxylation and further oxidations at both C-11 and C-12 to form a dialdehyde. Here, we have identified a drimenol synthase (PhDS) and a cytochrome P450 drimenol oxidase (PhDOX1) from Persicaria hydropiper. Expression of PhDS in yeast and plants resulted in production of drimenol alone. Co-expression of PhDS with PhDOX1 in yeast yielded drimendiol, the 12-hydroxylation product of drimenol, as a major product, and cinnamolide. When PhDS and PhDOX1 were transiently expressed by agro-infiltration in Nicotiana benthamiana leaves, drimenol was almost completely converted into cinnamolide and several additional drimenol derivatives were observed. In vitro assays showed that PhDOX1 only catalyses the conversion from drimenol to drimendiol, and not the further oxidation into an aldehyde. In yeast and heterologous plant hosts, the C-12 position of drimendiol is therefore likely to be further oxidized by endogenous enzymes into an aldehyde and subsequently converted to cinnamolide, presumably by spontaneous hemiacetal formation with the C-11 hydroxyl group followed by oxidation. Purified cinnamolide was confirmed by NMR and shown to be deterrent with an effective deterrent dose (ED50 ) of about 200-400 μg g-1 fresh weight against both whiteflies and aphids. The putative additional physiological and biochemical requirements for polygodial biosynthesis and stable storage in plant tissues are discussed.

Effect of prior drought and pathogen stress on Arabidopsis transcriptome changes to caterpillar herbivory

In nature, plants are exposed to biotic and abiotic stresses that often occur simultaneously. Therefore, plant responses to combinations of stresses are most representative of how plants respond to stresses. We used RNAseq to assess temporal changes in the transcriptome of Arabidopsis thaliana to herbivory by Pieris rapae caterpillars, either alone or in combination with prior exposure to drought or infection with the necrotrophic fungus Botrytis cinerea. Pre-exposure to drought stress or Botrytis infection resulted in a significantly different timing of the caterpillar-induced transcriptional changes. Additionally, the combination of drought and P. rapae induced an extensive downregulation of A. thaliana genes involved in defence against pathogens. Despite a more substantial growth reduction observed for plants exposed to drought plus P. rapae feeding compared with P. rapae feeding alone, this did not affect weight increase of this specialist caterpillar. Plants respond to combined stresses with phenotypic and transcriptional changes that differ from the single stress situation. The effect of a previous exposure to drought or B. cinerea infection on transcriptional changes to caterpillars is largely overridden by the stress imposed by caterpillars, indicating that plants shift their response to the most recent stress applied.

Resistance to sap-sucking insects in modern-day agriculture

Plants and herbivores have co-evolved in their natural habitats for about 350 million years, but since the domestication of crops, plant resistance against insects has taken a different turn. With the onset of monoculture-driven modern agriculture, selective pressure on insects to overcome resistances has dramatically increased. Therefore plant breeders have resorted to high-tech tools to continuously create new insect-resistant crops. Efforts in the past 30 years have resulted in elucidation of mechanisms of many effective plant defenses against insect herbivores. Here, we critically appraise these efforts and - with a focus on sap-sucking insects - discuss how these findings have contributed to herbivore-resistant crops. Moreover, in this review we try to assess where future challenges and opportunities lay ahead. Of particular importance will be a mandatory reduction in systemic pesticide usage and thus a greater reliance on alternative methods, such as improved plant genetics for plant resistance to insect herbivores.

Engineering of benzylglucosinolate in tobacco provides proof-of-concept for dead-end trap crops genetically modified to attract Plutella xylostella (diamondback moth)

Glucosinolates are biologically active natural products characteristic of crucifers, including oilseed rape, cabbage vegetables and the model plant Arabidopsis thaliana. Crucifer-specialist insect herbivores, like the economically important pest Plutella xylostella (diamondback moth), frequently use glucosinolates as oviposition stimuli. This suggests that the transfer of a glucosinolate biosynthetic pathway to a non-crucifer would stimulate oviposition on an otherwise non-attractive plant. Here, we demonstrate that stable genetic transfer of the six-step benzylglucosinolate pathway from A. thaliana to Nicotiana tabacum (tobacco) results in the production of benzylglucosinolate without causing morphological alterations. Benzylglucosinolate-producing tobacco plants were more attractive for oviposition by female P. xylostella moths than wild-type tobacco plants. As newly hatched P. xylostella larvae were unable to survive on tobacco, these results represent a proof-of-concept strategy for rendering non-host plants attractive for oviposition by specialist herbivores with the long-term goal of generating efficient dead-end trap crops for agriculturally important pests.

Non-protein amino acids in plant defense against insect herbivores: representative cases and opportunities for further functional analysis

Chemical defense against herbivores is of utmost importance for plants. Primary and secondary metabolites, including non-protein amino acids, have been implicated in plant defense against insect pests. High levels of non-protein amino acids have been identified in certain plant families, including legumes and grasses, where they have been associated with resistance to insect herbivory. Non-protein amino acids can have direct toxic effects via several mechanisms, including misincorporation into proteins, obstruction of primary metabolism, and mimicking and interfering with insect neurological processes. Additionally, certain non-protein amino acids allow nitrogen to be stored in a form that is metabolically inaccessible to herbivores and, in some cases, may act as signals for further plant defense responses. Specialized insect herbivores often possess specific mechanisms to avoid or detoxify non-protein amino acids from their host plants. Although hundreds of non-protein amino acids have been found in nature, biosynthetic pathways and defensive functions have been elucidated in only a few cases. Next-generation sequencing technologies and the development of additional plant and insect model species will facilitate further research on the production of non-protein amino acids, a widespread but relatively uninvestigated plant defense mechanism.

Volatile communication in plant-aphid interactions

Volatile communication plays an important role in mediating the interactions between plants, aphids, and other organisms in the environment. In response to aphid infestation, many plants initiate indirect defenses through the release of volatiles that attract ladybugs, parasitoid wasps, and other aphid-consuming predators. Aphid-induced volatile release in the model plant Arabidopsis thaliana requires the jasmonate signaling pathway. Volatile release is also induced by infection with aphid-transmitted viruses. Consistent with mathematical models of optimal transmission, viruses that are acquired rapidly by aphids induce volatile release to attract migratory aphids, but discourage long-term aphid feeding. Although the ecology of these interactions is well-studied, further research is needed to identify the molecular basis of aphid-induced and virus-induced changes in plant volatile release.

Immunity and other defenses in pea aphids, Acyrthosiphon pisum

BACKGROUND

Recent genomic analyses of arthropod defense mechanisms suggest conservation of key elements underlying responses to pathogens, parasites and stresses. At the center of pathogen-induced immune responses are signaling pathways triggered by the recognition of fungal, bacterial and viral signatures. These pathways result in the production of response molecules, such as antimicrobial peptides and lysozymes, which degrade or destroy invaders. Using the recently sequenced genome of the pea aphid (Acyrthosiphon pisum), we conducted the first extensive annotation of the immune and stress gene repertoire of a hemipterous insect, which is phylogenetically distantly related to previously characterized insects models.

RESULTS

Strikingly, pea aphids appear to be missing genes present in insect genomes characterized to date and thought critical for recognition, signaling and killing of microbes. In line with results of gene annotation, experimental analyses designed to characterize immune response through the isolation of RNA transcripts and proteins from immune-challenged pea aphids uncovered few immune-related products. Gene expression studies, however, indicated some expression of immune and stress-related genes.

CONCLUSIONS

The absence of genes suspected to be essential for the insect immune response suggests that the traditional view of insect immunity may not be as broadly applicable as once thought. The limitations of the aphid immune system may be representative of a broad range of insects, or may be aphid specific. We suggest that several aspects of the aphid life style, such as their association with microbial symbionts, could facilitate survival without strong immune protection.

Autogenous femoral head as grafting material for mandibular augmentation

Bone grafting is commonly used for augmentation of the atrophic edentulous maxilla and mandible. Although bone substitutes and allogeneic frozen bone grafts have been applied successfully, fresh autogenous bone grafts remain the 'gold standard' in maxillofacial reconstructive surgery. A disadvantage of harvesting autogenous bone is the resulting donor-site morbidity. The authors present a case in which an autogenous femoral head, which was removed because of a prosthetic hip replacement, was used for augmentation of the extreme atrophic mandible. Using this procedure avoids donor-site morbidity.

[A sudden redness and swelling of the face]

Two patients were referred to a department of oral and maxillofacial surgery with a redness and swelling of the face which had suddenly developed together with a mild illness. The diagnosis of erysipelas was made clinically. This skin infection is generally caused by betahaemolytic streptococci group-A. Treatment is generally in the first instance medicinal. The drugs of choice for treating erysipelas in the vast majority of cases are narrow-spectrum penicillins.

Indole-3-acetonitrile production from indole glucosinolates deters oviposition by Pieris rapae

Like many crucifer-specialist herbivores, Pieris rapae uses the presence of glucosinolates as a signal for oviposition and larval feeding. Arabidopsis thaliana glucosinolate-related mutants provide a unique resource for studying the in vivo role of these compounds in affecting P. rapae oviposition. Low indole glucosinolate cyp79B2 cyp79B3 mutants received fewer eggs than wild type, confirming prior research showing that indole glucosinolates are an important oviposition cue. Transgenic plants overexpressing epithiospecifier protein, which shifts glucosinolate breakdown toward nitrile formation, are less attractive to ovipositing P. rapae females. Exogenous application of indol-3-ylmethylglucosinolate breakdown products to cyp79B2 cyp79B3 mutants showed that oviposition was increased by indole-3-carbinol and decreased by indole-3-acetonitrile (IAN). P. rapae larvae tolerate a cruciferous diet by using a gut enzyme to redirect glucosinolate breakdown toward less toxic nitriles, including IAN, rather than isothiocyanates. The presence of IAN in larval regurgitant contributes to reduced oviposition by adult females on larvae-infested plants. Therefore, production of nitriles via epithiospecifier protein in cruciferous plants, which makes the plants more sensitive to generalist herbivores, may be a counter-adaptive mechanism for reducing oviposition by P. rapae and perhaps other crucifer-specialist insects.

Genomic resources for Myzus persicae: EST sequencing, SNP identification, and microarray design

Background

The green peach aphid, Myzus persicae (Sulzer), is a world-wide insect pest capable of infesting more than 40 plant families, including many crop species. However, despite the significant damage inflicted by M. persicae in agricultural systems through direct feeding damage and by its ability to transmit plant viruses, limited genomic information is available for this species.

Results

Sequencing of 16 M. persicae cDNA libraries generated 26,669 expressed sequence tags (ESTs). Aphids for library construction were raised on Arabidopsis thaliana, Nicotiana benthamiana, Brassica oleracea, B. napus, and Physalis floridana (with and without Potato leafroll virus infection). The M. persicae cDNA libraries include ones made from sexual and asexual whole aphids, guts, heads, and salivary glands. In silico comparison of cDNA libraries identified aphid genes with tissue-specific expression patterns, and gene expression that is induced by feeding on Nicotiana benthamiana. Furthermore, 2423 genes that are novel to science and potentially aphid-specific were identified. Comparison of cDNA data from three aphid lineages identified single nucleotide polymorphisms that can be used as genetic markers and, in some cases, may represent functional differences in the protein products. In particular, non-conservative amino acid substitutions in a highly expressed gut protease may be of adaptive significance for M. persicae feeding on different host plants. The Agilent eArray platform was used to design an M. persicae oligonucleotide microarray representing over 10,000 unique genes.

Conclusion

New genomic resources have been developed for M. persicae, an agriculturally important insect pest. These include previously unknown sequence data, a collection of expressed genes, molecular markers, and a DNA microarray that can be used to study aphid gene expression. These resources will help elucidate the adaptations that allow M. persicae to develop compatible interactions with its host plants, complementing ongoing work illuminating plant molecular responses to phloem-feeding insects.

Biochemistry and molecular biology of Arabidopsis-aphid interactions

To ensure their survival in natural habitats, plants must recognize and respond to a wide variety of insect herbivores. Aphids and other Hemiptera pose a particular challenge, because they cause relatively little direct tissue damage when inserting their slender stylets intercellularly to feed from the phloem sieve elements. Plant responses to this unusual feeding strategy almost certainly include recognition of aphid salivary components and the induction of phloem-specific defenses. Due to the excellent genetic and genomic resources that are available for Arabidopsis thaliana (Arabidopsis), this plant was chosen as a model system to study the metabolic and transcriptional responses to infestation by two aphids, Myzus persicae (green peach aphid, a broad generalist) and Brevicoryne brassicae (cabbage aphid, a crucifer-feeding specialist). Future research on Arabidopsis-aphid interactions will lead to the identification of aphid-specific elicitors, components of the defense-signaling pathway, and additional metabolic responses that are induced by aphid infestation.

RASSF6 is a novel member of the RASSF family of tumor suppressors

RASSF family proteins are tumor suppressors that are frequently downregulated during the development of human cancer. The best-characterized member of the family is RASSF1A, which is downregulated by promoter methylation in 40-90% of primary human tumors. We now identify and characterize a novel member of the RASSF family, RASSF6. Like the other family members, RASSF6 possesses a Ras Association domain and binds activated Ras. Exogenous expression of RASSF6 promoted apoptosis, synergized with activated K-Ras to induce cell death and inhibited the survival of specific tumor cell lines. Suppression of RASSF6 enhanced the tumorigenic phenotype of a human lung tumor cell line. Furthermore, RASSF6 is often downregulated in primary human tumors. RASSF6 shares some similar overall properties as other RASSF proteins. However, there are significant differences in biological activity between RASSF6 and other family members including a discrete tissue expression profile, cell killing specificity and impact on signaling pathways. Moreover, RASSF6 may play a role in dictating the degree of inflammatory response to the respiratory syncytial virus. Thus, RASSF6 is a novel RASSF family member that demonstrates the properties of a Ras effector and tumor suppressor but exhibits biological properties that are unique and distinct from those of other family members.

Radiological sacroiliitis, a hallmark of spondylitis, is linked with CARD15 gene polymorphisms in patients with Crohn's disease

BACKGROUND

Sacroiliitis is a common extraintestinal manifestation of Crohn's disease but its association with the HLA-B27 phenotype is less evident. Polymorphisms in the CARD15 gene have been linked to higher susceptibility for Crohn's disease. In particular, associations have been found with ileal and fibrostenosing disease, young age at onset of disease, and familial cases.

OBJECTIVES

To investigate whether the presence of sacroiliitis in patients with Crohn's disease is linked to the carriage of CARD15 polymorphisms.

METHODS

102 consecutive patients with Crohn's disease were clinically evaluated by a rheumatologist. Radiographs of the sacroiliac joints were taken and assessed blindly by two investigators. The RFLP-PCR technique was used to genotype all patients for three single nucleotide polymorphisms (SNP) in the CARD15 gene. Every SNP was verified by direct sequencing. The HLA-B27 phenotype was determined.

RESULTS

Radiological evidence of sacroiliitis with or without ankylosing spondylitis was found in 23 patients (23%), of whom only three were HLA-B27 positive. In contrast, 78% of patients with sacroiliitis carried a CARD15 variant v 48% of those without sacroiliitis (p = 0.01; odds ratio 3.8 (95% confidence interval, 1.3 to 11.5)). Multivariate analysis (logistic regression) showed that the association between sacroiliitis and CARD15 polymorphisms was independent of other CARD15 related phenotypes (ileal and fibrostenosing disease, young age at onset of disease, familial Crohn's disease) (p = 0.039).

CONCLUSIONS

CARD15 variants were identified as genetic predictors of Crohn's disease related sacroiliitis. An association was demonstrated between these polymorphisms and an extraintestinal manifestation of Crohn's disease.

[A cystic lesion in the mandibular angle]

A 27-year-old male patient was referred by his dentist to a department of Oral and Maxillofacial Surgery, because of a radiolucent lesion in the mandibular angle. There were no clinical signs or symptoms. The orthopantomogram showed a sharp, demarcated, oval (1.5 x 2.5 cm), unilocular radiolucency caudal of the mandibular canal. Additional radiographic evaluation (CT scan, sialogram) revealed an oval depression in the lingual cortex of the mandible filled with salivary gland tissue. The diagnosis Stafne defect was made. At radiographic follow-up after 1 year, no progression of the lesion was seen. Treatment is not needed.

Differential expression of the early lung cancer detection marker, heterogeneous nuclear ribonucleoprotein-A2/B1 (hnRNP-A2/B1) in normal breast and neoplastic breast cancer

Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP-A2/B1) is highly expressed during critical stages of lung development and carcinogenesis. To determine if the expression of hnRNP-A2/B1 is an informative biomarker in breast carcinogenesis, we analyzed hnRNP-A2/B1 overexpression by immunohistochemistry in archived specimens. Expression was detected in 48/85 (56.5%) primary invasive breast cancers and 7/72 (9.7%) specimens of normal breast tissue. Northern analysis of breast cancer cells also demonstrated higher level of hnRNP-A2/B1 expression compared to normal or transformed breast cells. Expression of hnRNP-A2/B1 in breast cancer cells was decreased by exposure to retinoids coordinately with decreased cell growth. These results warrant further evaluation of hnRNP-A2/B1 as a marker of breast carcinogenesis.

Ras uses the novel tumor suppressor RASSF1 as an effector to mediate apoptosis

Although activated Ras proteins are usually associated with driving growth and transformation, they may also induce senescence, apoptosis, and terminal differentiation. The subversion of these anti-neoplastic effects during Ras-dependent tumor development may be as important as the acquisition of the pro-neoplastic effects. None of the currently identified potential Ras effector proteins can satisfactorily explain the apoptotic action of Ras. Consequently, we have sought to identify novel Ras effectors that may be responsible for apoptosis induction. By examining the EST data base, we identified a potential Ras association domain in the tumor suppressor RASSF1. We now show that RASSF1 binds Ras in a GTP-dependent manner, both in vivo and directly in vitro. Moreover, activated Ras enhances and dominant negative Ras inhibits the cell death induced by transient transfection of RASSF1 into 293-T cells. This cell death appears to be apoptotic in nature, as RASSF1-transfected 293-T cells exhibit membrane blebbing and can be rescued by the addition of a caspase inhibitor. Thus, the RASSF1 tumor suppressor may serve as a novel Ras effector that mediates the apoptotic effects of oncogenic Ras.

Relationship of arachidonic acid metabolizing enzyme expression in epithelial cancer cell lines to the growth effect of selective biochemical inhibitors

Arachidonic acid (AA) metabolizing enzymes are emerging as significant mediators of growth stimulation for epithelial cells. The relative contribution of the various family members of AA metabolizing enzymes to epithelial cancer cell growth is not known. To study this question, we first analyzed a series of epithelial cancer cells to establish the relative frequency of expression for the various enzymes. We analyzed the expression of five AA metabolizing enzymes as well as 5-lipoxygenase activating protein (FLAP) in a panel of human epithelial cancer cell lines (n = 20) using reverse transcription-PCR. From this analysis, we found that cyclooxygenase-1 (COX-1), 5-lipoxygenase (5-LOX), and FLAP were universally expressed in all cancer cell lines tested. For the remaining enzymes, the expression of COX-2, 12-LOX, and 15-LOX varied among cell lines, 60, 35, and 90%, respectively. Although the pattern of expression varied among the different cell types, all of the enzymes were expressed in all major cancer histologies. Using a panel of selective biochemical AA metabolizing enzyme inhibitors, we then evaluated the effect of these agents on cell lines with known expression status for the AA metabolizing enzymes. For the enzymes that were not universally expressed, growth inhibition by selective biochemical inhibitors did not closely correlate with the expression status of specific enzymes (P > 0.05). For the universally expressed enzymes, the LOX inhibitors were more potent growth inhibitors than the COX inhibitors. The frequent expression of the AA metabolizing enzymes suggests that AA metabolism pathway may be modulated in response to xenobiotic exposure during carcinogenesis. Although establishing a priori AA metabolizing enzyme status was not consistently informative about what AA metabolizing enzyme inhibition would be most growth inhibitory, the frequent inhibition of many epithelial cancers by these biochemical inhibitors opens a new avenue for cancer therapy and intervention in carcinogenesis.

Phenotypic and functional characterization of a panel of cytotoxic murine NK cell clones that are heterogeneous in their enhancement of Ig secretion in vitro

NK cells not only function as cytotoxic effector cells, but also have immunoregulatory roles including the enhancement of Ig secretion. To have a stable and uniform population of NK cells to study their role in Ig secretion, we generated murine NK clones. Thus, culture of splenocytes from mice that were homozygous for a mutation in the p53 tumor suppressor gene (p53-KO) with IL-2 and poly(IC) resulted in a long-term NK line, from which four stable clones were derived. This approach also yielded a long-term NK line from splenocytes of normal C57BL/6 mice. Identification of the clones as members of the NK lineage was based on large granular morphology, expression of NK-TR and absence of TCR gene rearrangement. Flow cytometry revealed that all clones expressed IL-2R alpha and beta, chains and B220, but no CD3, NK1.1, DX5 or Ly-49. RT-PCR analysis showed heterogeneity in NK1.1 gene expression, and demonstrated expression of perforin and several granzymes in all clones. Three out of four clones lysed YAC-1, but not P815 target cells, corresponding to a pattern of NK specificity. All NK clones enhanced Ig secretion in an in vitro model for T cell-independent type 2 antigens, albeit to varying degrees. We found no correlation between the degree of helper activity of the NK clones and the level of their cytotoxic activity on YAC-1 targets. Thus, we established murine NK clones, and show that they mediate both cytotoxicity and enhancement of Ig secretion.

Peptide-amidating enzymes are expressed in the stellate epithelial cells of the thymic medulla

C-terminal amidation is a post-translational processing step necessary to convey biological activity to a large number of regulatory peptides. In this study we have demonstrated that the peptidyl-glycine alpha-amidating monooxygenase enzyme complex (PAM) responsible for this activity is located in the medullary stellate epithelial cells of the thymus and in cultured epithelial cells bearing a medullary phenotype, using Northern blot, immunocytochemistry, in situ hybridization, and enzyme assays. Immunocytochemical localization revealed a granular pattern in the cytoplasm of the stellate cells, which were also positive for cytokeratins and a B-lymphocyte-associated antigen. The presence of PAM activity in medium conditioned by thymic epithelial cell lines suggests that PAM is a secreted product of these cells. Among the four epithelial cell lines examined, there was a direct correlation between PAM activity and content of oxytocin, an amidated peptide. Taken together, these data provide convincing evidence that thymic epithelial cells have the capacity to generate amidated peptides that may influence T-cell differentiation and suggest that the amidating enzymes could play an important role in the regulation of thymic physiology.

Purification and characterization of a protein that permits early detection of lung cancer. Identification of heterogeneous nuclear ribonucleoprotein-A2/B1 as the antigen for monoclonal antibody 703D4

We have reported that a mouse monoclonal antibody 703D4, detects lung cancer 2 years earlier than routine chest x-ray or cytomorphology. We purified the 703D4 antigen to elucidate its role in early lung cancer biology, using Western blot detection after SDS-polyacrylamide gel electrophoresis. Purification steps included anion exchange chromatography, preparative isoelectric focusing, polymer-based C18-like, and analytical C4 reverse phase high performance liquid chromatography. After 25-50,000-fold purification, the principal immunostaining protein was > 95% pure by Coomassie staining. The NH2 terminus was blocked, so CNBr digestion was used to generate internal peptides. Three sequences, including one across a site of alternate exon splicing, all identified a single protein, heterogeneous nuclear ribonucleoprotein-A2 (hnRNP-A2). A minor co-purifying immunoreactive protein resolved at the final C4 high performance liquid chromatography step is the splice variant hnRNP-B1. Northern analysis of RNA from primary normal bronchial epithelial cells demonstrated a low level of hnRNP-A2/B1 expression, consistent with immunohistochemical staining of clinical samples, and increased hnRNP-A2/B1 expression was found in lung cancer cells. hnRNP-A2/B1 expression is under proliferation-dependent control in normal bronchial epithelial cell primary cultures, but not in SV40-transformed bronchial epithelial cells or tumor cell lines. With our clinical data, this information suggests that hnRNP-A2/B1 is an early marker of lung epithelial transformation and carcinogenesis.

Growth control of lung cancer by interruption of 5-lipoxygenase-mediated growth factor signaling

Signal transduction pathways shared by different autocrine growth factors may provide an efficient approach to accomplish clinically significant control of lung cancer growth. In this study, we demonstrate that two autocrine growth factors activate 5-lipoxygenase action of the arachidonic acid metabolic pathway in lung cancer cell lines. Both growth factors increased the production of 5(S)-hydrooxyeicosa-6E,8Z,11Z,14Z-tetraeno ic acid (5-HETE), a major early 5-lipoxygenase metabolic product. Exogenously added 5-HETE stimulated lung cancer cell growth in vitro. Inhibition of 5-lipoxygenase metabolism by selective antagonists resulted in significant growth reduction for a number of lung cancer cell lines. Primary clinical specimens and lung cancer cell lines express the message for the 5-lipoxygenase enzymes responsible for the generation of active metabolites. In vivo evaluation demonstrated that interruption of 5-lipoxygenase signaling resulted in enhanced levels of programmed cell death. These findings demonstrate that 5-lipoxygenase activation is involved with growth factor-mediated growth stimulation for lung cancer cell lines. Pharmacological intervention with lipoxygenase inhibitors may be an important new clinical strategy to regulate growth factor-dependent stages of lung carcinogenesis.

Expression in human lung cancer cell lines of genes of prohormone processing and the neuroendocrine phenotype

Lung tumor cells and cell lines, principally the histologically classified small cell lung cancer, are characterized by the expression of neuroendocrine (NE) features including AADC (aromatic amino acid decarboxylase, previously called DOPA decarboxylase) and the production of many peptide hormones. The general mechanisms by which most aspects of the NE phenotype affect the clinical behavior of lung tumor cells are unknown, but it is well recognized that peptide hormones can have systemic effects (paraneoplastic syndromes) and several have been shown to be autocrine growth factors for cancer cells. In order to determine the relationship between expression of different aspects of the NE phenotype in lung cancer cell lines, we have compared expression of a gene required for biosynthesis of some active peptide hormones (PAM, peptidylglycine alpha-amidating monooxygenase) to the gene for AADC in 32 lung cancer cell lines. Expression of these genes was quantified by both steady state Northern blot analysis and radiochemical enzymatic activity measurements. To ensure a range of expression of NE markers, non-small cell lung cancer (NSCLC) cell lines were chosen to include several which had previously been shown to express NE markers, and several small cell lung cancer (SCLC) cell lines with previous low levels of AADC were included. PAM enzyme activity and Northern blot analysis showed a two to three log variation in levels of expression in both the small cell and non-small cell lines. A smaller range was found for AADC expression. Using the highly sensitive PAM enzyme assays, all cell lines were found to express detectable PAM. PAM activities were secreted into the growth medium of all cell lines. There was no simple correlation apparent between AADC and PAM gene expression in the lung cancer cell lines. However, classic small cell lines demonstrated high levels of expression of both PAM and AADC genes, as did the carcinoid subset of the NSCLC lines. NSCLC lines expressed levels of PAM mRNA and enzyme activities equivalent to those of SCLC but had infrequent expression of AADC (principally only carcinoid NSCLC expressed AADC). These data demonstrate that separate aspects of the NE phenotype can be differentially expressed in lung cancer histological sub-types. Expression of PAM enzymes in all sub-types of lung cancer suggests that peptide prohormone activation may be a common mechanism for autocrine growth stimulation even in non-Ne NSCLC cell lines, or may reflect maintenance in cell lines of a common pathway of lung tumor promotion.

Human peptidylglycine alpha-amidating monooxygenase transcripts derived by alternative mRNA splicing of an unreported exon

We are characterizing the alternatively spliced human peptidylglycine alpha-amidating monooxygenase (hPAM)-encoding mRNA transcripts expressed by human cells. Reverse transcription coupled to the polymerase chain reaction (RT-PCR) has been used to identify four alternatively spliced variants that differ in the region joining the two catalytic domains. Two of the transcripts represent previously reported splice variants differentiated by the presence (hPAM-A) or absence (hPAM-B) of a 321-nucleotide (nt) linker (optional exon A) which in the rat produce functionally distinct enzymes. Different mRNAs represent two splice variants, hPAM-C and hPAM-D, that show the presence of an exon unreported for PAM in any other species. This new exon, designated exon C, is 54 nt in length, encodes an 18-amino-acid (aa) peptide containing a conserved dibasic aa endoproteolytic processing motif, and is located 3' of exon A in human genomic DNA. We propose that cell-specific regulation of mRNA splicing would provide a mechanism for control of prohormone activation by these variants of the PAM enzyme.