Will the real Bemisia tabaci please stand up?

Since Panayiotis Gennadius first identified the whitefly, Aleyrodes tabaci in 1889, there have been numerous revisions of the taxonomy of what has since become one of the world’s most damaging insect pests. Most of the taxonomic revisions have been based on synonymising different species under the name Bemisia tabaci. It is now considered that there is sufficient biological, behavioural and molecular genetic data to support its being a cryptic species complex composed of at least 34 morphologically indistinguishable species. The first step in revising the taxonomy of this complex involves matching the A. tabaci collected in 1889 to one of the members of the species complex using molecular genetic data. To do this we extracted and then amplified a 496 bp fragment from the 39 end of the mitochondrial DNA cytochrome oxidase one (mtCOI) gene belonging to a single whitefly taken from Gennadius’ original 1889 collection. The sequence identity of this 123 year-old specimen enabled unambiguous assignment to a single haplotype known from 13 Mediterranean locations across Greece and Tunisia. This enabled us to unambiguously assign the Gennadius A. tabaci to the member of the B. tabaci cryptic species complex known as Mediterranean or as it is commonly, but erroneously referred to, as the ‘Q-biotype’. Mediterranean is therefore the real B. tabaci. This study demonstrates the importance of matching museum syntypes with known species to assist in the delimitation of cryptic species based on the organism’s biology and molecular genetic data. This study is the first step towards the reclassification of B. tabaci which is central to an improved understanding how best to manage this globally important agricultural and horticultural insect pest complex

On species delimitation, hybridization and population structure of cassava whitefly in Africa.

The Bemisia cassava whitefly complex includes species that cause severe crop damage through vectoring cassava viruses in eastern Africa. Currently, this whitefly complex is divided into species and subgroups (SG) based on very limited molecular markers that do not allow clear definition of species and population structure. Based on 14,358 genome-wide SNPs from 62 Bemisia cassava whitefly individuals belonging to sub-Saharan African species (SSA1, SSA2 and SSA4), and using a well-curated mtCOI gene database, we show clear incongruities in previous taxonomic approaches underpinned by effects from pseudogenes. We show that the SSA4 species is nested within SSA2, and that populations of the SSA1 species comprise well-defined south-eastern (Madagascar, Tanzania) and north-western (Nigeria, Democratic Republic of Congo, Burundi) putative sub-species. Signatures of allopatric incipient speciation, and the presence of a 'hybrid zone' separating the two putative sub-species were also detected. These findings provide insights into the evolution and molecular ecology of a highly cryptic hemipteran insect complex in African, and allow the systematic use of genomic data to be incorporated in the development of management strategies for this cassava pest

Vector-Virus Mutualism Accelerates Population Increase of an Invasive Whitefly

The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. This variation in relationships may affect the process of biological invasion and the displacement of indigenous species by invaders when the invasive and indigenous organisms occur with niche overlap but differ in the interactions. The notorious invasive B biotype of the whitefly complex Bemisia tabaci entered China in the late 1990s and is now the predominant or only biotype in many regions of the country. Tobacco curly shoot virus (TbCSV) and Tomato yellow leaf curl China virus (TYLCCNV) are two whitefly-transmitted begomoviruses that have become widespread recently in south China. We compared the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on healthy, TbCSV-infected and TYLCCNV-infected tobacco plants. Compared to its performance on healthy plants, the invasive B biotype increased its fecundity and longevity by 12 and 6 fold when feeding on TbCSV-infected plants, and by 18 and 7 fold when feeding on TYLCCNV-infected plants. Population density of the B biotype on TbCSV- and TYLCCNV-infected plants reached 2 and 13 times that on healthy plants respectively in 56 days. In contrast, the indigenous ZHJ1 performed similarly on healthy and virus-infected plants. Virus-infection status of the whiteflies per se of both biotypes showed limited effects on performance of vectors on cotton, a nonhost plant of the viruses. The indirect mutualism between the B biotype whitefly and these viruses via their host plants, and the apparent lack of such mutualism for the indigenous whitefly, may contribute to the ability of the B whitefly biotype to invade, the displacement of indigenous whiteflies, and the disease pandemics of the viruses associated with this vector

African ancestry of New World, Bemisia tabaci-whitefly species

Bemisia tabaci whitefly species are some of the world’s most devastating agricultural pests and plant-virus disease vectors. Elucidation of the phylogenetic relationships in the group is the basis for understanding their evolution, biogeography, gene-functions and development of novel control technologies. We report here the discovery of five new Sub-Saharan Africa (SSA) B. tabaci putative species, using the partial mitochondrial cytochrome oxidase 1 gene: SSA9, SSA10, SSA11, SSA12 and SSA13. Two of them, SSA10 and SSA11 clustered with the New World species and shared 84.8‒86.5% sequence identities. SSA10 and SSA11 provide new evidence for a close evolutionary link between the Old and New World species. Re-analysis of the evolutionary history of B. tabaci species group indicates that the new African species (SSA10 and SSA11) diverged from the New World clade c. 25 million years ago. The new putative species enable us to: (i) re-evaluate current models of B. tabaci evolution, (ii) recognise increased diversity within this cryptic species group and (iii) re-estimate divergence dates in evolutionary time

Functional Inequality in Latin America: News from the Twentieth Century

We report on a novel approach for the measurement of gas adsorption in microporous solids using X-ray computed tomography (CT) that we refer to as digital adsorption. Similar to conventional macroscopic methods, the proposed protocol combines observations with an inert and an adsorbing gas to produce equilibrium isotherms in terms of the truly measurable quantity in an adsorption experiment, namely the surface excess. Most significantly, X-ray CT allows probing the adsorption process in three dimensions, so as to build spatially-resolved adsorption isotherms with a resolution of approximately 10 mm3 within a fixed-bed column. Experiments have been carried out at 25 C and in the pressure range 1-30bar using CO2 on activated carbon, zeolite 13X and glass beads (as control material), and results are validated against literature data. A scaling approach was applied to analyze the whole population of measured adsorption isotherms (~7600), leading to single universal adsorption isotherm curves that are descriptive of all voxels for a given adsorbate-adsorbent system. By analyzing the adsorption heterogeneity at multiple length scales (1 mm3 to 1 cm3), packing heterogeneity was identified as the main contributor for the larger spatial variability in the adsorbed amount observed for the activated carbon rods as compared to zeolite pellets. We also show that this technique is readily applicable to a large spectrum of commercial porous solids, and that it can be further extended to weakly adsorbing materials with appropriate protocols that reduce measurement uncertainties. As such, the obtained results prove the feasibility of digital adsorption and highlight substantial opportunities for its wider use in the field of adsorptive characterization of porous solids

Tomato Pathogenesis-related Protein Genes are Expressed in Response to Trialeurodes vaporariorum and Bemisia tabaci Biotype B Feeding

The temporal and spatial expression of tomato wound- and defense-response genes to Bemisia tabaci biotype B (the silverleaf whitefly) and Trialeurodes vaporariorum (the greenhouse whitefly) feeding were characterized. Both species of whiteflies evoked similar changes in tomato gene expression. The levels of RNAs for the methyl jasmonic acid (MeJA)- or ethylene-regulated genes that encode the basic β-1,3-glucanase (GluB), basic chitinase (Chi9), and Pathogenesis-related protein-1 (PR-1) were monitored. GluB and Chi9 RNAs were abundant in infested leaves from the time nymphs initiated feeding (day 5). In addition, GluB RNAs accumulated in apical non-infested leaves. PR-1 RNAs also accumulated after whitefly feeding. In contrast, the ethylene- and salicylic acid (SA)-regulated Chi3 and PR-4 genes had RNAs that accumulated at low levels and GluAC RNAs that were undetectable in whitefly-infested tomato leaves. The changes in Phenylalanine ammonia lyase5 (PAL5) were variable; in some, but not all infestations, PAL5 RNAs increased in response to whitefly feeding. PAL5 RNA levels increased in response to MeJA, ethylene, and abscisic acid, and declined in response to SA. Transcripts from the wound-response genes, leucine aminopeptidase (LapA1) and proteinase inhibitor 2 (pin2), were not detected following whitefly feeding. Furthermore, whitefly infestation of transgenic LapA1:GUS tomato plants showed that whitefly feeding did not activate the LapA1 promoter, although crushing of the leaf lamina increased GUS activity up to 40 fold. These studies indicate that tomato plants perceive B. tabaci and T. vaporariorum in a manner similar to baterical pathogens and distinct from tissue-damaging insects

Expression Profiling of FSHD-1 and FSHD-2 Cells during Myogenic Differentiation Evidences Common and Distinctive Gene Dysregulation Patterns

BACKGROUND: Determine global gene dysregulation affecting 4q-linked (FSHD-1) and non 4q-linked (FSHD-2) cells during early stages of myogenic differentiation. This approach has been never applied to FSHD pathogenesis. METHODOLOGY/PRINCIPAL FINDINGS: By in vitro differentiation of FSHD-1 and FSHD-2 myoblasts and gene chip analysis we derived that gene expression profile is altered only in FSHD-1 myoblasts and FSHD-2 myotubes. The changes seen in FSHD-1 regarded a general defect in cell cycle progression, probably due to the upregulation of myogenic markers PAX3 and MYOD1, and a deficit of factors (SUV39H1 and HMGB2) involved in D4Z4 chromatin conformation. On the other hand, FSHD-2 mytubes were characterized by a general defect in RNA metabolism, protein synthesis and degradation and, to a lesser extent, in cell cycle. Common dysregulations regarded genes involved in response to oxidative stress and in sterol biosynthetic process. Interestingly, our results also suggest that miRNAs might be implied in both FSHD-1 and FSHD-2 gene dysregulation. Finally, in both cell differentiation systems, we did not observe a gradient of altered gene expression throughout the 4q35 chromosome. CONCLUSIONS/SIGNIFICANCE: FSHD-1 and FSHD-2 cells showed, in different steps of myogenic differentiation, a global deregulation of gene expression rather than an alteration of expression of 4q35 specific genes. In general, FSHD-1 and FSHD-2 global gene deregulation interested common and distinctive biological processes. In this regard, defects of cell cycle progression (FSHD-1 and to a lesser extent FSHD-2), protein synthesis and degradation (FSHD-2), response to oxidative stress (FSHD-1 and FSHD-2), and cholesterol homeostasis (FSHD-1 and FSHD-2) may in general impair a correct myogenesis. Taken together our results recapitulate previously reported defects of FSHD-1, and add new insights into the gene deregulation characterizing both FSHD-1 and FSHD-2, in which miRNAs may play a role