Candidatus Portiera Research Articles

Effects of Cadmium Stress on Bacterial and Fungal Communities in the Whitefly Bemisia tabaci.

Heavy metal contamination is among the most prominent environmental problems in China, posing serious threats to both ecosystem and human health. Among the diverse heavy metal contaminants, cadmium is the most serious. The whitefly Bemisia tabaci is a cosmopolitan pest capable of causing severe damage to a broad range of agricultural crops, especially vegetables. At present, little is known about the effects of cadmium stress on B. tabaci, including on its bacterial and fungal communities. In the current study, we investigated the effects of cadmium on bacterial and fungal communities in whiteflies. Meta-barcode sequencing of the 16S rRNA gene revealed that the whitefly bacterial community contained 264 operational taxonomic units (OTUs) belonging to 201 known genera and 245 known species. The top five most frequent bacterial genera were Rickettsia, Rhodococcus, Candidatus Portiera, Candidatus Hamiltonella, and Achromobacter. Meta-barcode sequencing of the fungal ITS locus revealed that the whitefly fungal community contained 357 OTUs belonging to 187 known genera and 248 known species. The top five most frequent fungal genera were Wallemia, unclassified_f_Dipodascaceae, Apiotrichum, Penicillium, and unclassified_o_Saccharomycetales. Cadmium exposure reduced the fungal OTU richness but increased the bacterial Shannon and Simpson diversity indices in whiteflies. In addition, upon exposure to cadmium, the microbial community composition in whiteflies changed significantly, with increased prevalence of the bacterial genera Rhodococcus and Exiguobacterium and fungal genus Wallemia. Our results indicate that the whitefly microbiota likely contributed to their adaptation and resistance to cadmium and suggested that whiteflies may contain microbes that could help remediate cadmium contamination in natural environments and agricultural fields.

First Report of Aleurocanthus spiniferus on Ailanthus altissima: Profiling of the Insect Microbiome and MicroRNAs.

We report the first occurrence of the orange spiny whitefly (Aleurocanthus spiniferus; OSW) on the tree of heaven (Ailanthus altissima) in Bari, Apulia region, Italy. After our first observation in 2016, the infestation recurred regularly during the following years and expanded to the neighboring trees. Since then, we have also found the insect on numerous patches of the tree of heaven and other plant species in the Bari province. Nevertheless, the tree of heaven was not particularly threatened by the insect, so that a possible contribution by OSW for the control of such an invasive plant cannot be hypothesized hitherto. This work was also aimed at profiling the microbiome of OSW feeding on A. altissima. For this purpose, we used the denaturing gradient gel electrophoresis (DGGE) and the deep sequencing of small RNAs (sRNAs). Both techniques unveiled the presence of “Candidatus Portiera” (primary endosymbiont), Wolbachia sp. and Rickettsia sp., endosymbionts already reported for other Aleyrodidae. Deep sequencing data were analyzed by four computational pipelines in order to understand the reliability of the detection of fungi, bacteria, and viruses: Kraken, Kaiju, Velvet, and VelvetOptimiser. Some contigs assembled by Velvet or VelvetOptimiser were associated with insects, but not necessarily in the Aleurocanthus genus or Aleyrodidae family, suggesting the non-specificity of sRNAs or possible traces of parasitoids in the sample (e.g., Eretmocerus sp.). Finally, deep sequencing data were used to describe the microtranscriptome of OSW: 56 canonical and at least four high-confidence novel microRNAs (miRNAs) were identified. The overall miRNA abundance in OSW was in agreement with previous works on Bemisia tabaci, and bantam-3p, miR-276a-3p, miR-317-3p, miR-750-3p, and mir-8-3p were the most represented miRNAs.

Analysis of the bacterial communities and endosymbionts of natural populations of Bemisia tabaci in several crop fields from Mexico semi-arid zone

Bemisia tabaci (Aleyrodidae family) is an insect vector of plant viruses that affects a wide variety of crops around the world. In the following study, we analyzed the variation in the bacterial communities associated with natural populations of B. tabaci (MEAM1) of four different crops from six regions from Mexico semi-arid zone (Baja California Sur). PCR was used to amplify the mitochondrial cytochrome oxidase I gene (mtCOI), and then to carry out the phylogenetic analysis for genetic identification of the isolated B. tabaci. Next generation sequencing coupled with 16S metagenomic analysis was applied in order to characterize B. tabaci inner microbial community. Finally, bacterial obligate symbiont and facultative symbiont were confirmed by PCR amplification and by phylogenetic analysis. Ours results pointed toward that B. tabaci MEAM1 inner bacterial communities were predominantly structured by Proteobacteria phylum. Moreover, the most represented endosymbionts were the obligate endosymbiont from the genus “Candidatus Portiera”, as well as two facultative symbionts belonging to genera Rickettsia and Hamiltonella; both obligate and facultative endosymbionts were present for all samples, and their relative abundance varied was crop-independent. Geographic localization and insect diet play a central role to maintain bacterial community structure of the B. tabaci MEAM1 whitefly at phylum taxonomic level. Agricultural practices were a factor that affected samples of bacterial community structure similarities, reflected in samples clustering. Host plants that are part of B. tabaci diet did not influence directly, in spite of sap nutrient differences, into obligate and facultative endosymbionts relative abundance.

Fluorescence in situ hybridization analysis of endosymbiont genera reveals novel infection patterns in a tomato-infesting Bemisia tabaci population from Brazil

The Bemisia tabaci cryptic species complex harbors a diversified flora of primary and secondary endosymbionts, which plays crucial roles in many aspects of the insect biology. The endosymbiont infection pattern is dependent upon many factors, including host plant and geographic origin. In Brazil, the invasion of B. tabaci Middle East-Asia Minor-1 (MEAM 1) populations was observed in tomato (Solanum lycopersicum L.) fields in the 1990s, which was followed by severe begomovirus epidemics. Here we confirmed the vertical transmission of “Candidatus Portiera” and the localization of secondary endosymbionts in distinct B. tabaci developmental stages. Hamiltonella defensa was detected in bacteriocytes but also scattered in the leg muscles as well as in the male heads. Wolbachia-specific signals were found in eggs, nymphs, male adults, and female gonads in predominant association with bacteriocytes. These results were somewhat surprising since Wolbachia infection is rarely found in MEAM 1 populations from the Old World. Our results reinforce the notion that endosymbiont infection pattern may vary according to the insect population, gender, developmental stage, and geographic origin. This characterization will provide tools to study the endosymbiont function in the transmission ability/efficiency of a complex of tomato-infecting bipartite begomoviruses by B. tabaci under Neotropical conditions.