Cassiterite U-Pb age in the Bawapin tin deposit, Tanintharyi Region, southern Myanmar

1.Objective Southeast Asia has a 3500 km tin metallogenic belt in the world,extending from southern Yunnan Province to Bangka,Indonesia.This region is also the world’s largest one regarding tin production,which accounts for 85%of historical tin production globally(Lehmann B,2021).Myanmar is one of the main tin producers within this region(33000 t in 2020)and has become the key supplier after China and Indonesia.Research on tin mineralization in Myanmar mostly focused on ore-related granites,for zircon geochronology,magma evolution,and tectonic settings(Mao W et al.,2020).

Geochronology and petrogeochemistry of Late Permian volcanic rocks in the B.Xiengnou area,Northwestern Laos:Petrogenesis and tectonic significance

The Nan Suture and Sukhothai Arc Terrane are products of the eastward subduction of the Paleotethyan Ocean during the Late Carboniferous to Triassic.However,their footprints in northwestern Laos are poorly constrained.New geochronological and geochemical data presented in this study demonstrate a Late Permian origin for the andesitic rocks in the B.Xiengnou area rather than Late Triassic.The breccia-bearing andesitic tuff in the B.On ultramafic complex yield a zircon U-Pb age of 260±1.4 Ma,geochemically displaying a MORB-like signature.The andesitic tuff in the B.Kiophoulan-B.Houayhak belt gave the U-Pb age of 254±1.3 Ma,with arc-like geochemical affinity.By combining geochronological and geochemical data from the Nan Suture and Sukhothai Arc Terrane,the authors suggest that the andesitic rocks in the B.On ultramafic complex formed in a back-arc basin background,which connected the Jinghong and Nan back-arc basin during the Permian;while the andesitic tuff in the B.Kiophoulan-B.Houayhak belt erupted in the Sukhothai continental arc setting.

Viral infection of tobacco plants improves performance of Bemisia tabaci but more so for an invasive than for an indigenous biotype of the whitefly

The ecological effects of plant-virus-vector interactions on invasion of alien plant viral vectors have been rarely investigated. We examined the transmission of Tomato yellow leaf curl China virus (TYLCCNV) by the invasive Q biotype and the indigenous ZHJ2 biotype of the whitefly Bemisia tabaci, a plant viral vector, as well as the influence of TYLCCNV-infection of plants on the performance of the two whitefly biotypes. Both whitefly biotypes were able to acquire viruses from infected plants and retained them in their bodies, but were unable to transmit them to either tobacco or tomato plants. However, when the Q biotype fed on tobacco plants infected with TYLCCNV, its fecundity and longevity were increased by 7- and 1-fold, respectively, compared to those of the Q biotype fed on uninfected tobacco plants. When the ZHJ2 biotype fed on virus-infected plants, its fecundity and longevity were increased by only 2- and 0.5-fold, respectively. These data show that the Q biotype acquired higher beneficial effects from TYLCCNV-infection of tobacco plants than the ZHJ2 biotype. Thus, the Q biotype whitefly may have advantages in its invasion and displacement of the indigenous ZHJ2 biotype.

The presence of six cryptic species of the whitefly Bemisia tabaci complex in China as revealed by crossing experiments

Recent phylogenetic analysis using mitochondrial cytochrome oxidase I （mtCOI） sequences ofBemisia tabaci worldwide indicates that the whitefly comprises at least 24 morphologically indistinguishable but genetically distinct cryptic species. While evidence of reproductive isolation has been reported for some of the putative species, more extensive crossing experiments are required to clarify the systematics of this species com- plex. In this study, we established laboratory cultures for six putative species ofB. tabaci collected in China. We conducted 22 inter-species crosses among the six putative species. The data and those reported previously were collated, and the combined dataset covered all the 30 possible inter-species crosses among the six putative species. Intra-species controls always produced female and male progeny and the proportions of females in the first gen- eration （F1） ranged from 56% to 70%. However, in inter-species crosses female progeny were rarely produced, and the few F1 females produced in four of the 30 inter-species crosses were either sterile or significantly weaker in viability. These results demonstrate a pattern of complete reproductive isolation among the six putative species and show that they are six cryptic species in the B. tabaci complex.

Genome-wide identification and characterization of HSP gene superfamily in whitefly (Bemisia tabacl)and expression profiling analysis under temperature stress

Heat shock proteins (HSP)are essential molecular chaperones that play important roles in the stress stimulation of insects.Bemisia tabaci,a phloem feeder and invasive species,can cause extensive crop damage through direct feeding and transmission of plant viruses.Here we employed comprehensive genomics approaches to identity HSP superfamily members in the Middle East Asia Minor 1 whitefly genome.In total,we identified 26 Hsp genes,including three Hsp90,17 Hsp70,one Hsp60 and five sHSP (small heat shock protein)genes.The HSP gene superfamily of whitefly is expanded compared with the other five insects surveyed here.The gene structures among the same families are relatively conserved.Meanwhile,the motif compositions and secondary structures of BtHsp proteins were predicted.In addition,quantitative polymerase chain reaction analysis showed that the expression patterns of BtHsp gene superfamily were diverse across different tissues of whiteflies.Most Hsp genes were induced or repressed by thermal stress (40℃)and cold treatment (4℃)in whitefly.Silencing the expression of BtHsp70-6 significantly decreased the survival rate of whitefly under 45℃.All the results showed the Hsps conferred thermo-tolerance or cold-tolerance to whiteflies that protect them from being affected by detrimental temperature conditions.Our observations highlighted the molecular evolutionary properties and the response mechanism to temperature assaults of Hsp genes in whitefly.

Diversity of secondary endosymbionts among different putative species of the whitefly Bemisia tabaci

Endosymbionts are important components of arthropod biology. The white- fly Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） is a cryptic species complex composed of 〉28 putative species. In addition to the primary endosymbiont Portiera aley- rodidarum, six secondary endosymbionts （S-endosymbionts）, Hamiltonella, Rickettsia, Wolbachia, Cardinium, Arsenophonus and Fritschea, have been identified in B. tabaci thus far. Here, we tested five of the six S-endosymbiont lineages （excluding Fritschea） from 340 whitely individuals representing six putative species from China. Harniltonella was detected only in the two exotic invaders, Middle East-Asia Minor 1 （MEAM 1） and Mediter- ranean （MED）. Rickettsia was absent in Asia II 1 and MED, scarce in Asia II 3 （13%）, but abundant in Asia II 7 （63.2%）, China 1 （84.7%） and MEAM1 （100%）. Wolbachia, Cardinium and Arsenophonus were absent in the invasive MEAM1 and MED but mostly abundant in the native putative species. Furthermore, phylogenetic analyses revealed that some S-endosymbionts have several clades and different B. tabaci putative species can harbor different clades of a given S-endosymbiont, demonstrating further the complexity of S-endosymbionts in B. tabaci. All together, our results demonstrate the variation and diversity of S-endosymbionts in different putative species ofB. tabaci, especially between invasive and native whiteflies.

Crossing experiments and behavioral observations reveal reproductive incompatibility among three putative species of the whitefly Bemisia tabaci

The whitefly Bemisia tabaci has a global distribution and extensive genetic diversity. Recent phylogenetic analyses as well as crossing experiments suggest that B. tabaci is a complex composed of 〉 20 cryptic species, but more crossing studies are required to examine the reproductive compatibility among the putative species and thus further clarify the systematics of this species complex. We conducted crossing experiments and behavioral observations to investigate the reproductive compatibility between the Mediterranean, Asia II 3, and Asia II 1 putative species ofB. tabaci collected from Zhejiang, China. Female progeny were never produced in inter-species crosses, demonstrating a lack of egg fertilization; while 55%-75% females were produced in all the intra-species treatments. Continuous behavioral observations showed that frequent courtship events occurred in both intra-species treatments and inter-putative species crosses. However, copulation events occurred only in the three intra-species treatments with one exception： that one copulation event occurred between Asia II 3 and Mediterranean in the crosses where two cohorts of females and males of different putative species were enclosed together in a small arena but were not allowed access to their intra-specific mates for a long period of time. These data demonstrated complete reproductive isolation between the Mediterranean, Asia II 3, and Asia II 1 putative species, and further showed that the isolation is due to lack of copulation. Demonstration of reproductive isolation between the Mediterranean and two indigenous putative species from China provides further evidence for the existence of cryptic species within the B. tabaci complex.

Transgenic plants expressing the AalT/GNA fusion protein show increased resistance and toxicity to both chewing and sucking pests

The adoption of pest-resistant transgenic plants to reduce yield losses and de- crease pesticide use has been successful. To achieve the goal of controlling both chewing and sucking pests in a given transgenic plant, we generated transgenic tobacco, Arabidopsis, and rice plants expressing the fusion protein, AalT/GNA, in which an insecticidal scor- pion venom neurotoxin （Androctonus australis toxin, AalT） is fused to snowdrop lectin （Galanthus nivalis agglutinin, GNA）. Compared with transgenic tobacco and Arabidop- sis plants expressing AaIT or GNA, transgenic plants expressing AalT/GNA exhibited increased resistance and toxicity to one chewing pest, the cotton bollworm, Helicoverpa armigera. Transgenic tobacco and rice plants expressing AalT/GNA showed increased resistance and toxicity to two sucking pests, the whitefly, Bemisia tabaci, and the rice brown planthopper, Nilaparvata lugens, respectively. Moreover, in the field, transgenic rice plants expressing AalT/GNA exhibited a significant improvement in grain yield when infested with N. lugens. This study shows that expressing the AalT/GNA fusion protein in transgenic plants can be a useful approach for controlling pests, particularly sucking pests which are not susceptible to the toxin in Bt crops.

Gene expression profiling of the whitefly （Bemisia tabaci） Middle East- Asia Minor 1 feeding on healthy and Tomato yellow leaf curl China virus-infected tobacco

Begomoviruses are exclusively transmitted by whitefly （Bemisia tabaci） in a circulative, non-propagative manner. The influences of begomoviruses on whitefly vector are complex with both direct and indirect effects. However, the molecular mechanisms underlying these effects are poorly understood and the transcriptional profiles of whitefly on healthy and virus-infected plants have not yet been studied. Using suppression subtractive hybridization, we investigated the differentially expressed genes in whitefly Middle East - Asia Minor 1 feeding on healthy and Tomato yellow leaf curl China virus （TYLCCNV） infected tobacco. From the forward cDNA library, 124 differentially expressed expression sequence tags （ESTs） were obtained which represent up-regulated genes in the whiteflies feeding on the infected tobacco. From the reverse library, 112 ESTs were isolated which represent down-regulated genes. Among the up-regulated genes, we identified several genes that are probably involved in direct interaction between whitefly and TYLCCN~, including a 26/29-kDa proteinase that appears to participate in the elimination of foreign proteins, heparan sulfate proteoglycan which mediates the entry of several viruses into host cells and two genes of Rickettsia-a secondary endosymbiotic bacterium of whitefly. In addition, we identified a number of genes involved in metabolism, transcription and translation which might be the result of indirect effects of TYLCCNV on the whitefly via host plants. Collectively, our results suggest that TYLCCNV-infected tobacco changes the gene expression profiles of whitefly via both direct and indirect interactions. This study revealed a number of genes involved in whitefly-TYLCCNV-tobacco interactions and provided useful information for future study on this complex system.

Temporal changes of symbiont density and host fitness after rifampicin treatment in a whitefly of the Bemisia tabaci species complex

Microbial symbionts are essential or important partners to phloem-feeding insects. Antibiotics have been used to selectively eliminate symbionts from their host insects and establish host lines with or without certain symbionts for investigating functions of the symbionts. In this study, using the antibiotic rifampicin we attempted to selectively eliminate certain symbionts from a population of the Middle East-Asia Minor 1 whitefly of the Bemisia tabaci species complex, which harbors the primary symbiont ＂Candidatus Portiera aleyrodidarum＂ and two secondary symbionts ＂Candidatus Hamiltonella defensa＂ and Rickettsia. Neither the primary nor the secondary symbionts were completely depleted in the adults （F0） that fed for 48 h on a diet treated with rifampicin at concentrations of 1 100/zg/mL. However, both the primary and secondary symbionts were nearly completely depleted in the offspring （F 1） of the rifampicin-treated adults. Although the F1 adults produced some eggs （F2）, most of the eggs failed to hatch and none of them reached the second instar, and consequently the rifampicin-treated whitefly colony vanished at the F2 generation. Interestingly, quantitative polymerase chain reaction assays showed that in the rifampicin-treated whiteflies, the density of the primary symbiont was reduced at an obviously slower pace than the secondary symbionts. Mating experiments between rifampicin-treated and untreated adults demonstrated that the negative effects ofrifampicin on host fitness were expressed when the females were treated by the antibiotic, and whether males were treated or not by the antibiotic had little contribution to the negative effects. These observations indicate that with this whitefly population it is not feasible to selectively eliminate the secondary symbionts using rifampicin without affecting the primary symbiont and establish host lines for experimental studies. However, the extinction of the whitefly colony at the second generation after rifampicin treatment indicates the potential of the antibiotic as a control agent of the whitefly pest.

Sequencing and comparison of the Rickettsia genomes from the whitefly Bemisia tabaci Middle East Asia Minor I

The whitefly, Bemisia tabaci, harbors the primary symbiont ＇Candidatus Portiera aleyrodidarum＇ and a variety of secondary symbionts. Among these secondary symbionts, Rickettsia is the only one that can be detected both inside and outside the bacteriomes. Infection with Rickettsia has been reported to influence several aspects of the whitefly biology, such as fitness, sex ratio, virus transmission and resistance to pesticides. However, mechanisms underlying these differences remain unclear, largely due to the lack of genomic information of Rickettsia. In this study, we sequenced the genome of two Rickettsia strains isolated from the Middle East Asia Minor 1 （MEAM1） species of the B. tabaci complex in China and Israel. Both Rickettsia genomes were of high coding den- sity and AT-rich, containing more than 1000 coding sequences, much larger than that of the coexisted primary symbiont, Portiera. Moreover, the two Rickettsia strains isolated from China and Israel shared most of the genes with 100% identity and only nine genes showed sequence differences. The phylogenetic analysis using orthologs shared in the genus, inferred the proximity of Rickettsia in MEAM1 and Rickettsia bellii. Functional analysis revealed that Rickettsia was unable to synthesize amino acids required for complementing the whitefly nutrition. Besides, a type IV secretion system and a number of virulence- related genes were detected in the Rickettsia genome. The presence of virulence-related genes might benefit the symbiotic life of the bacteria, and hint on potential effects of Rickettsia on whiteflies. The genome sequences of Rickettsia provided a basis for further understanding the function of Rickettsia in whiteflies.

Progress in improving thermodynamics and kinetics of new hydrogen storage materials

Hydrogen storage material has been much developed recently because of its potential for proton exchange membrane （PEM） fuel cell applications. A successful solid-state reversible storage material should meet the requirements of high storage capacity, suitable thermodynamic properties, and fast adsorption and desorption kinetics. Complex hydrides, including boron hydride and alanate, ammonia borane, metal organic frameworks （MOFs）, covalent organic frameworks （COFs） and zeolitic imidazolate frameworks （ZIFs）, are remarkable hydrogen storage materials because of their advantages of high energy density and safety. This feature article focuses mainly on the thermodynamics and kinetics of these hydrogen storage materials in the past few years.

Cloning of a putative extracellular Cu/Zn superoxide dismutase and functional differences of superoxide dismutases in invasive and indigenous whiteflies

Superoxide dismutases （SODs） are a group of important antioxidant defense enzymes. In this study, a putative extracellular Cu/Zn superoxide dismutase （ecCuZnSOD） complementary DNA was cloned and characterized from the whitefly, Bemisia tabaci. Quantitative polymerase chain reaction analysis showed that the expression level of BtecCuZnSOD was more than 10-fold higher in the invasive Middle East Asia Minor 1 （MEAM1） than in the native Asia II 3 species of the B. tabaci species complex. After exposure to low temperature （4 ℃）, the expression of Bt-ecCuZnSOD gene was significantly up-regulated in MEAM1 but not in Asia II 3. Furthermore, the expression level ofB. tabaci intracellular CuZnSOD （Bt-icCuZnSOD）, Bt-ecCuZnSOD and mitochondrial MnSOD （Bt-mMnSOD） was compared after transferring MEAM1 and Asia II 3 whiteflies from favorable （cotton） to unfavorable host plants （tobacco）. On cotton, both CuZnSOD genes were expressed at a higher level in MEAM1 compared with Asia II 3. Interestingly, after transferring onto tobacco, the expression of Bt-ecCuZnSOD was significantly induced in Asia II 3 but not in MEAM1. On the other hand, while Bt-mMnSOD was expressed equally in both species on cotton, Bt-mMnSOD messenger RNA was up-regulated in MEAM 1 on tobacco. Consistently, enzymatic activity assays of CuZnSOD and MnSOD demonstrated that CuZnSOD might play an important protective role against oxidative stress in Asia II 3, whereas MnSOD activation was critical for MEAM1 whiteflies during host adaptation. Taken together, our results suggest that the successful invasion ofMEAM 1 is correlated with its constitutive high activity of CuZnSOD and inducible expression of MnSOD under stress conditions.

Different headspace profiles in wild crucifer species in response to Plutella xylostella herbivory and exogenous jasmonic acid application

Although exogenous treatment of plants withjasmonic acid （JA） may result in induced responses similar to plant defences induced by herbivory, few studies have compared the details of insect herbivory and JA-mimicked responses. We compared volatiles of two crucifer species, Cardamine impatiens and Lepidium virginicum, in response to Plutella xylostella larval feeding and exogenous application of JA, over the entire period of time when induced changes were detectable. Significant differences in the composition and timing of volatiles occurred between herbivory and JA treatments in both plants. The quantity ofnitrile and isothiocyanate released in response to herbivory was significantly larger than that upon JA treatment. In each of the two plant species, most volatile components were emitted immediately upon larval feeding and their quantity dropped rapidly once feeding ceased. In contrast, the emission of volatiles in response to JA treatment lasted for a longer period of time, and the maximum emission rate was recorded 2 and 3 days after JA treatment in L. virginicum and C. impatiens respectively. These findings are discussed in the context of signal-transduction pathways and mechanisms involved in induced emissions of plant volatiles, as well as induced defences mediated by plant volatiles.

Impact of a novel Rickettsia symbiont on the life history and virus transmission capacity of its host whitefly(Bemisia tabaci)

Rickettsia consists of some of the most prevalent symbionts of insects and often plays a significant role in the biology of its hosts.Recently,a maternally inherited Torix group Rickettsia,provisionally named as RiTBt,was recorded in a species of notorious pest whitefly,tentatively named as Asia II 1,from the Bemisia tabaci complex.The role of this Rickettsia in the biology of its host is unknown.Here we investigated the impact of RiTBt on the performance and virus transmission capacity of Asia II 1.RiTBt did not significantly affect the life history parameters of the whitefly when the host insect was reared on tobacco,tomato,and cotton,three host plants with relatively low,medium and high suitability to the whitefly.Intriguingly,RiTBt slightly enhanced whitefly transmission of cotton leaf curl Multan virus(CLCuMuV),a virus that is transmitted by the whitefly in the field and has caused extensive damage to cotton production.Specifically,compared with whiteflies without RiTBt,following a 48 h virus acquisition whiteflies with RiTBt had higher titer of virus and showed higher efficiency of virus transmission.A rickettsial secretory protein BtR242 was identified as a putative virus-binding protein,and was observed to interact with the coat protein of CLCuMuV in vitro.Viral infection of the whitefly downregulated gene transcript levels of the BtR242 gene.These observations indicate that RiTBt has limited impact on the biology of the Asia II 1 whitefly,and whether this symbiont has functions in the biology of other host whiteflies warrants future investigation.

Further insight into reproductive incompatibility between putative cryptic species of the Bemisia tabaci whitefly complex

The whitefly Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae）, with its global distribution and extensive genetic diversity, is now known to be a complex of over 35 cryptic species. However, a satisfactory resolution of the systematics of this species complex is yet to be achieved. Here, we designed experiments to examine reproductive compatibility among species with different levels of mitochondrial cytochrome oxidase I （mtCOI） divergence. The data show that putative species with mtCOI divergence of 〉 8% between them consistently exhibited complete reproductive isolation. However, two of the putative species, Asia II 9 and Asia II 3, with mtCOI divergence of 4.47% between them, exhibited near complete reproductive compatibility in one direction of their cross, and partial reproductive compatibility in the other direction. Together with some recent reports on this topic from the literature, our data indicates that, while divergence in the mtCOI sequences provides a valid molecular marker for species delimitation in most clades, more genetic markers and more sophisticated molecular phylogeny will be required to achieve adequate delimitation of all species in this whitefly complex. While many attempts have been made to examine the reproductive compatibility among genetic groups of the B. tabaci complex, our study represents the first effort to conduct crossing experiments with putative species that were chosen with considerations of their genetic divergence. In light of the new data, we discuss the best strategy and protocols to conduct further molecular phylogenetic analysis and crossing trials, in order to reveal the overall pattern of reproductive incompatibility among species of this whitefly complex.

Genomic and transcriptomic analyses reveal metabolic complementarity between whiteflies and their symbionts

Nutritional mutualism between insects and symbiotic bacteria is widespread.The various sap-feeding whitefly species within the Bemisia tabaci complex associate with the same obligate symbiont(Portiera)and multiple secondary symbionts.It is often assumed that some of the symbionts residing in the whiteflies play crucial roles in the nutritional physiology of their insect hosts.Although effort has been made to understand the functions of the whitefly symbionts,the metabolic complementarity offered by these symbionts to the hosts is not yet well understood.We examined two secondary symbionts,Arsenophonus and Wolbachia,in two species of the B.tabaci whitefly complex,provisionally named as Asia II 3 and China 1.Genomic sequence analyses revealed that Arsenophonus and Wolbachia retained genes responsible for the biosynthesis of B vitamins.We then conducted transcriptomic surveys of the bacteriomes in these two species of whiteflies together with that in another species named MED of this whitefly complex previously reported.The analyses indicated that several key genes in B vitamin syntheses from the three whitefly species were identical.Our findings suggest that,similar to another secondary symbiont Hamiltonella,Arsenophonus and Wolbachia function in the nutrient provision of host whiteflies.Although phylogenetically distant species of symbionts are associated with their respective hosts,they have evolved and retained similar functions in biosynthesis of some B vitamins.Such metabolic complementarity between whiteflies and symbionts represents an important feature of their coevolution.