Resistance mechanisms to plant viruses: an overview

To obtain virus-resistant host plants, a range of operational strategies can be followed nowadays. While for decades plant breeders have been able to introduce natural resistance genes in susceptible genotypes without knowing precisely what these resistance traits were, currently a growing number of (mostly) dominant resistance genes have been cloned and analyzed. This has led not only to a better understanding of the plant's natural defence systems, but also opened the way to use these genes beyond species borders. Besides using natural resistance traits, also several novel, "engineered" forms of virus resistance have been developed over the past 15 years. The first successes were obtained embarking from the principle of pathogen-derived resistance (PDR) by transforming host plants with viral genes or sequences with the purpose to block a specific step during virus multiplication in the plant. As an unforeseen spin-off of these investments, the phenomenon of post-translational gene silencing (PTGS) was discovered, which to date is by far the most successful way to engineer resistance. It is generally believed that PTGS reflects a natural defence system of the plant, and part of the hypothesized components required for PTGS have been identified. As counteracting strategy, and confirming PTGS to be a natural phenomenon, a considerable number of viruses have acquired gene functions by which they can suppress PTGS. In addition to PDR and PTGS, further strategies for engineered virus resistance have been explored, including the use of pokeweed antiviral protein (PAP), 2',5'-oligoadenylate synthetase and "plantibodies". This paper will give a brief overview of the major strategies that have become operational during the past 10 years.     

In situ localisation of beet necrotic yellow vein virus (BNYVV) in rootlets of susceptible and resistant beet plants

Summary Mechanisms of resistance to beet necrotic yellow vein virus (BNYVV) were studied by comparing the multiplication and distribution of BNYVV in root tissue of some beet accessions. Seedlings were infected either by soil containing resting spores ofPolymyxa betae with BNYVV, or by a viruliferous zoospore suspension. With both inoculation methods high virus concentrations were obtained in rootlets of the susceptible cultivar Regina. Using infested soil, low virus concentrations were found in the partially resistant cultivar Rima and in the resistant accessions Holly and WB42. When a zoospore suspension was used, similar virus concentrations occurred in Rima and Holly as in Regina, while a low virus concentration was found in WB42. By in situ localisation studies, using immunogold-silver labelling, virus was detected in Regina after infection by soil or a zoospore suspension, but it could only be detected in the resistant accessions after infection by a zoospore suspension. In rootlets of Regina, Rima and Holly, virus was found in the epidermis, cortex parenchyma, endodermis, and interstitial parenchyma, but in general not inside the vascular tissue. In WB42 the virus, occurring in small aggregates, seemed to be restricted to the epidermis and some cortex parenchyma cells. Comparing both the multiplication and distribution of BNYVV in rootlets of the accessions studied, it is concluded that the virus resistance mechanism in Rima and Holly is different from that in WB42.     

Molecular cloning and sequence analysis of the 3′-terminal region of iris severe mosaic virus RNA

Summary Sequence analysis of iris severe mosaic potyvirus genomic RNA revealed an unusual E/G cleavage site between the deduced large nuclear-inclusion protein and coat protein sequences. The latter showed an N-terminus of only 15 amino acids. The 3 non-translated region of the viral RNA was 340 nucleotides long.     

Lesbian,Gay, Bisexual,and Transgender (LGBT) Service Members: Life After Don’t Ask,Don’t Tell

Lesbian, gay, and bisexual service members can serve openly in the military with the repeal of the Don’t Ask, Don’t Tell policy. The fate of transgender service members remains uncertain as the policy preventing them from serving in the military remains under review. The health care needs of these populations remain for the most part unknown, with total acceptance and integration in the military yet to be achieved. In this paper, we review the literature on the health care needs of lesbian, gay, bisexual, and transgender (LGBT) service members, relying heavily on what is known about LGBT civilian and veteran populations. Significant research gaps about the health care needs of LGBT service members are identified, along with recommendations for closing those gaps. In addition, recommendations for improving LGBT acceptance and integration within the military are provided.     

Relationship between O2 delivery and O2 consumption in the adult respiratory distress syndrome

We evaluated the relationship between O2 delivery and oxygen consumption (VO2) in ten patients with the adult respiratory distress syndrome (ARDS) over the course of their illness (mean 7 +/- 5 days) while they were receiving positive mechanical ventilation with varying levels of positive end-expiratory pressure (PEEP). Mean values and standard deviations for O2 delivery and VO2 were 15.2 +/- 4.8 ml/min/kg and 4.1 +/- 1.2 ml/min/kg, respectively. In our ten patients, below an O2 delivery of 21 ml/min/kg, VO2 was linearly related to O2 delivery (VO2 = 0.32 X O2 delivery--0.53, n = 83, r = 0.76). However, at an O2 delivery rate higher than 21 ml/min/kg, there was no correlation between VO2 and O2 delivery. Mixed venous O2 content (CvO2) and arteriovenous oxygen content difference (C(a-v)O2) did not correlate with O2 delivery, nor was there a significant correlation between cardiac output (Qt) and mixed venous O2 tension (PvO2) or saturation (SvO2). We conclude that in patients with ARDS on mechanical ventilation with PEEP, VO2 and O2 delivery are linearly related except at high levels of O2 delivery. PvO2 and (C(a-v)O2) do not correlate with O2 delivery and are not sensitive indicators of tissue oxygenation in ARDS.     

Cyberbullying Perpetration and Victimization Among Middle-School Students

Objectives. We examined correlations between gender, race, sexual identity, and technology use, and patterns of cyberbullying experiences and behaviors among middle-school students.Methods. We collected a probability sample of 1285 students alongside the 2012 Youth Risk Behavior Survey in Los Angeles Unified School District middle schools. We used logistic regressions to assess the correlates of being a cyberbully perpetrator, victim, and perpetrator–victim (i.e., bidirectional cyberbullying behavior).Results. In this sample, 6.6% reported being a cyberbully victim, 5.0% reported being a perpetrator, and 4.3% reported being a perpetrator–victim. Cyberbullying behavior frequently occurred on Facebook or via text messaging. Cyberbully perpetrators, victims, and perpetrators–victims all were more likely to report using the Internet for at least 3 hours per day. Sexual-minority students and students who texted at least 50 times per day were more likely to report cyberbullying victimization. Girls were more likely to report being perpetrators–victims.Conclusions. Cyberbullying interventions should account for gender and sexual identity, as well as the possible benefits of educational interventions for intensive Internet users and frequent texters.Cyberbullying is the “willful and repeated harm inflicted [on another] through the use of computers, cell phones, or other electronic devices.”1^(p5) Among 6th- through 10th-grade students nationally, 4% reported being cyberbullying perpetrators, 5% reported being a victim of cyberbullying, and 5% reported being perpetrators–victims (meaning that they have both perpetrated and been victimized by cyberbullying) during the previous 2 months.2 Among middle-school students in the southeastern and northwestern United States, a nonprobability sample of 3767 students by Kowalski and Limber3 found that 11% reported being a victim of cyberbullying, 4% were cyberbullying perpetrators, and 7% were perpetrators–victims during the previous 2 months. Cyberbullying may be more insidious than traditional bullying, because cyberbullying can quickly reach wide audiences (e.g., e-mails sent to an entire school), can be perpetrated anonymously, and is not bound to in-person interactions.4,5 Although cyberbullying has garnered widespread media attention, to our knowledge, no previous study has explored correlates of cyberbullying with a representative probability sample in an urban middle-school sample.Cyberbullying is associated with a host of health and behavioral health consequences. Research has suggested that cyberbullying may have a greater effect on depression and suicidal ideation than traditional offline bullying.6 Both perpetration and victimization are associated with mental health consequences, including lower self-esteem,7 recent depressive symptoms,5,8,9 and suicidal ideation.5,8,10 Cyberbullying perpetrators are more likely to have problems with their behavior, peer relationships, and emotions, and are less likely to be prosocial than their peers who are neither cyberbullying perpetrators nor victims of cyberbullying.11 Specifically, female cyberbullying perpetrators express greater anxiety and depression than their female peers who are not cyberbullying perpetrators.12 Cyberbullying victimization is also strongly associated with substance use, violent behavior, and risky sexual behavior among high-school students.10Cyberbullying disproportionately affects youths who are already vulnerable to mental health and behavioral health disparities, including members of sexual minorities (i.e., gay, lesbian, bisexual), girls, and racial and ethnic minorities. More than half of sexual-minority middle- and high-school students nationally report being a cyberbully victim during the previous year, with almost one fifth reporting often or frequent victimization.13 Female students are significantly more likely to be cyberbully perpetrators–victims than their male peers.9,14 Studies have reported that male students are significantly more likely to be cyberbullying perpetrators2,15 and significantly less likely to be cyberbully victims.2,6,9 Middle-school boys are more likely to cyberbully others because of their race, sexual identity, or both.16 African American students are more likely to be cyberbully perpetrators and Hispanic students are more likely to be cyberbully perpetrators–victims than their White peers.2Cyberbullying may occur across a variety of technology platforms, and the specific qualities of each platform may affect how cyberbullying is perpetrated and experienced. Earlier studies suggested that instant messaging, chat rooms, and message boards were the most common mediums for middle-school students who experienced cyberbullying.3,17 More recently, youths have migrated to social media platforms such as Facebook,18–20 necessitating an examination of cyberbullying across more contemporary and emerging platforms for youth interaction.More frequent use of technology has also been associated with cyberbullying. Students who use the Internet for at least 3 hours per day and those who use instant messaging and Web cams are significantly more likely to have been cyberbully victims at least 7 times during the previous year.17 Frequent Internet users are significantly more likely to be cyberbully perpetrators, victims, and perpetrators–victims.14Research has shown that even though cyberbullying takes place in a virtual space, most cyberbullying perpetrators know their victims and vice versa. Moreover, 73% of victims reported being “pretty sure” or “totally sure” about the identity of their cyberbully, with 51% of cyberbullying perpetrators identified as a classmate, 43% as someone who they only knew online, and 20% as an in-person, nonclassmate relation.17 Cyberbullying perpetrators of middle-school victims were most often a classmate or a stranger; cyberbullying perpetrators most often reported that they cyberbullied classmates, friends, and strangers.3This study expanded previous work with high-school samples2 and nonprobability samples of middle-school students3,17 to explore the role of sexual identity, gender, race, and technology use patterns in a random sample of urban middle-school students in Los Angeles County, California. The study focused on demographic characteristics including sexual identity, patterns of technology use (i.e., frequency of Internet use, texting, parental rules regarding Internet use), and platforms on which middle-school students experience cyberbullying (i.e., Facebook, Twitter, e-mail, text messaging) to inform interventions to disrupt this maladaptive behavior and help protect early adolescents from the consequences of cyberbullying.     

General and Ethnic-Biased Bullying Among Latino Students: Exploring Risks of Depression,Suicidal Ideation,and Substance Use

Using a cross-sectional sample of 534 Latino students from middle and high schools in a large North Carolina school district, we examined the relation of general and ethnic-biased bullying to depression and the indirect pathways through depression to suicidal ideation and substance use outcomes. A structural equation model tested the direct and indirect paths. The final model fit was excellent, χ²(90)?=?127.6, p?=?.0056, RMSEA?=?0.028, CFI?=?0.974, TLI?=?0.961. Ethnic-biased and verbal or relational bullying had a direct effect on depression, but general and physical bullying did not. Indirect effects through depression were found for ethnic-biased and verbal or relational bullying in relation to suicidal ideation, alcohol, and illicit drug use. Child nativity was marginally associated with ethnic-biased bullying, indicating foreign-born students may experience greater ethnic-biased bullying. Implications for future research and bullying prevention are discussed.