Co-infection and localization of secondary symbionts in two whitefly species

<p>Abstract</p> <p>Background</p> <p>Whiteflies are cosmopolitan phloem-feeding pests that cause serious damage to many crops worldwide due to direct feeding and vectoring of many plant viruses. The sweetpotato whitefly <it>Bemisia tabaci </it>(Gennadius) and the greenhouse whitefly <it>Trialeurodes vaporariorum </it>(Westwood) are two of the most widespread and damaging whitefly species. To complete their unbalanced diet, whiteflies harbor the obligatory bacterium <it>Portiera aleyrodidarum. B. tabaci </it>further harbors a diverse array of secondary symbionts, including <it>Hamiltonella, Arsenophonus, Cardinium, Wolbachia, Rickettsia </it>and <it>Fritschea</it>. <it>T. vaporariorum </it>is only known to harbor <it>P. aleyrodidarum </it>and <it>Arsenophonus</it>. We conducted a study to survey the distribution of whitefly species in Croatia, their infection status by secondary symbionts, and the spatial distribution of these symbionts in the developmental stages of the two whitefly species.</p> <p>Results</p> <p><it>T. vaporariorum </it>was found to be the predominant whitefly species across Croatia, while only the Q biotype of <it>B. tabaci </it>was found across the coastal part of the country. <it>Arsenophonus </it>and <it>Hamiltonella </it>were detected in collected <it>T. vaporariorum </it>populations, however, not all populations harbored both symbionts, and both symbionts showed 100% infection rate in some of the populations. Only the Q biotype of <it>B. tabaci </it>was found in the populations tested and they harbored <it>Hamiltonella</it>, <it>Rickettsia, Wolbachia </it>and <it>Cardinium</it>, while <it>Arsenophonus </it>and <it>Fritschea </it>were not detected in any <it>B. tabaci </it>populations. None of the detected symbionts appeared in all populations tested, and multiple infections were detected in some of the populations. All endosymbionts tested were localized inside the bacteriocyte in both species, but only <it>Rickettsia </it>and <it>Cardinium </it>in <it>B. tabaci </it>showed additional localization outside the bacteriocyte.</p> <p>Conclusions</p> <p>Our study revealed unique co-infection patterns by secondary symbionts in <it>B. tabaci </it>and <it>T. vaporariorum</it>. Co-sharing of the bacteriocyte by the primary and different secondary symbionts is maintained through vertical transmission via the egg, and is unique to whiteflies. This system provides opportunities to study interactions among symbionts that co-inhabit the same cell in the same host: these can be cooperative or antagonistic, may affect the symbiotic contents over time, and may also affect the host by competing with the primary symbiont for space and resources.</p

An Intranuclear Sodalis-Like Symbiont and Spiroplasma Coinfect the Carrot Psyllid, Bactericera trigonica (Hemiptera, Psylloidea)

Endosymbionts harbored inside insects play critical roles in the biology of their insect host and can influence the transmission of pathogens by insect vectors. Bactericera trigonica infests umbelliferous plants and transmits the bacterial plant pathogen Candidatus Liberibacter solanacearum (CLso), causing carrot yellows disease. To characterize the bacterial diversity of B. trigonica, as a first step, we used PCR-restriction fragment length polymorphism (PCR-RFLP) and denaturing gradient gel electrophoresis (DGGE) analyses of 16S rDNA to identify Sodalis and Spiroplasma endosymbionts. The prevalence of both symbionts in field-collected psyllid populations was determined: Sodalis was detected in 100% of field populations, while Spiroplasma was present in 82.5% of individuals. Phylogenetic analysis using 16S rDNA revealed that Sodalis infecting B. trigonica was more closely related to symbionts infecting weevils, stink bugs and tsetse flies than to those from psyllid species. Using fluorescent in situ hybridization and immunostaining, Sodalis was found to be localized inside the nuclei of the midgut cells and bacteriocytes. Spiroplasma was restricted to the cytoplasm of the midgut cells. We further show that a recently reported Bactericera trigonica densovirus (BtDNV), a densovirus infecting B. trigonica was detected in 100% of psyllids and has reduced titers inside CLso-infected psyllids by more than two-fold compared to CLso uninfected psyllids. The findings of this study will help to increase our understanding of psyllid–endosymbiont interactions

Plant-Mediated Silencing of the Whitefly Bemisia tabaci Cyclophilin B and Heat Shock Protein 70 Impairs Insect Development and Virus Transmission

The whitefly B. tabaci is a global pest and transmits extremely important plant viruses especially begomoviruses, that cause substantial crop losses. B. tabaci is one of the top invasive species worldwide and have developed resistance to all major pesticide classes. One of the promising alternative ways for controlling this pest is studying its genetic makeup for identifying specific target proteins which are critical for its development and ability to transmit viruses. Tomato yellow leaf curl virus (TYLCV) is the most economically important and well-studied begomovirus transmitted by B. tabaci, in a persistent-circulative manner. Recently, we reported that B. tabaci Cyclophilin B (CypB) and heat shock protein 70 proteins (hsp70) interact and co-localize with TYLCV in the whitefly midgut, on the virus transmission pathway, and that both proteins have a significant role in virus transmission. Here, we extended the previous work and used the Tobacco rattle virus (TRV) plant-mediated RNA silencing system for knocking down both genes and testing the effect of their silencing on whitefly viability and virus transmission. Portions of these two genes were cloned into TRV constructs and tomato plants were infected and used for whitefly feeding and transmission experiments. Following whitefly feeding on TRV-plants, the expression levels of cypB and hsp70 in adult B. tabaci significantly decreased over 72 h feeding period. The knockdown in the expression of both genes was further shown in the first generation of silenced whiteflies, where phenotypic abnormalities in the adult, wing, nymph and bacteriosomes development and structure were observed. Additionally, high mortality rates that reached more than 80% among nymphs and adults were obtained. Finally, silenced whitefly adults with both genes showed decreased ability to transmit TYLCV under lab conditions. Our results suggest that plant-mediated silencing of both cypB and hsp70 have profound effects on whitefly development and its ability to transmit TYLCV

Invasive insect species importance and possible pathways of their spreading in Serbia

Invasive insect species are alien species that have significant impact on biodiversity of certain area or specific country, and also can cause severe damage to cultivated plants. Many insects spread actively, but very often benefit from human activities and use transport of trades and passengers to travel all around the globe. Directions and stopover of these stowaways are usually unpredictable hence the importance of insect monitoring and investigation of their spreading pathways are of great importance for the country, and even for the whole potentially endangered region. One of the currently most important Hemipteran species, recorded for the first time in 2015 in Serbia, is Brown Marmorated Stink Bug, Halyomorpha halys Stål (Pentatomidae). The species has been monitored for five consecutive years and nowadays it is considered as well established in the country. On the other side, another cosmopolitan Hemipteran species, in Serbia known as tobacco white fly, Bemisia tabaci (Gennadius) (Aleyrodidae) was recorded on the territory of Serbia in 2016 and 2017, but since then specimens of this species have not been recorded neither outside nor in green houses during regular monitoring, why it is considered as not established

Mating behaviour, life history and adaptation to insecticides determine species exclusion between whiteflies

Summary 1. Negative interspecific interactions, such as resource competition or reproductive interference, can lead to the displacement of species (species exclusion). 2. Here, we investigated the effect of life history, mating behaviour and adaptation to insecticides on species exclusion between cryptic whitefly species that make up the Bemisia tabaci species complex. We conducted population cage experiments independently in China, Australia, the United States and Israel to observe patterns of species exclusion between an invasive species commonly referred to as the B biotype and three other species commonly known as biotypes ZHJ1, AN and Q. 3. Although experimental conditions and species varied between regions, we were able to predict the observed patterns of exclusion in each region using a stochastic model that incorporated data on development time, mating behaviour and resistance to insecticides. 4. Between-species variation in mating behaviour was a more significant factor affecting species exclusion than variation in development time. Specifically, the ability of B to copulate more effectively than other species resulted in a faster rate of population increase for B, as well as a reduced rate of population growth for other species, leading to species exclusion. The greater ability of B to evolve resistance to insecticides also contributed to exclusion of other species in some cases. 5. Results indicate that an integrative analysis of the consequences of variation in life-history traits, mating behaviours and adaption to insecticides could provide a robust framework for predicting species exclusion following whitefly invasions

First report of Trichogramma danausicida and Trichogramma cacaeciae reared from Thaumatotibia leucotreta eggs in Israel

The egg parasitpoids Trichogramma danausicida (Nagaraja) and Trichogramma cacaeciae (Marchal) (Hymenoptera: Trichogrammatidae), are reported for the first time in Israel. Moreover, our discovery of T. danausicida is the first report of this parasitoid species outside of India. The occurrence of those trichogrammatids was first discovered and documented in May 2016 during a survey of egg parasitoids of the False codling moth Thaumatotibia leucotreta (Lepidoptera: Tortricidae). The field survey was conducted on castor bean fruits (Ricinus communis) in the Israeli central coastal plain. The identity of the parasitoids was revealed by means of sequencing a portion of the cytochrome oxidase I gene (COI) of the studied parasitoids