Michael Strand Archives - Page 3 of 4 - Center for Tropical and Emerging Global Diseases

Riboflavin instability is a key factor underlying the requirement of a gut microbiota for mosquito development

Donna Huber on April 9, 2021

We previously determined that several diets used to rear Aedes aegypti and other mosquito species support the development of larvae with a gut microbiota but do not support the development of axenic larvae. In contrast, axenic larvae have been shown to develop when fed other diets. To understand the mechanisms underlying this dichotomy, we developed a defined diet that could be manipulated in concert with microbiota composition and environmental conditions. Initial studies showed that axenic larvae could not grow under standard rearing conditions (27 °C, 16-h light: 8-h dark photoperiod) when fed a defined diet but could develop when maintained in darkness. Downstream assays identified riboflavin decay to lumichrome as the key factor that prevented axenic larvae from growing under standard conditions, while gut community members like Escherichia coli rescued development by being able to synthesize riboflavin. Earlier results showed that conventional and gnotobiotic but not axenic larvae exhibit midgut hypoxia under standard rearing conditions, which correlated with activation of several pathways with essential growth functions. In this study, axenic larvae in darkness also exhibited midgut hypoxia and activation of growth signaling but rapidly shifted to midgut normoxia and arrested growth in light, which indicated that gut hypoxia was not due to aerobic respiration by the gut microbiota but did depend on riboflavin that only resident microbes could provide under standard conditions. Overall, our results identify riboflavin provisioning as an essential function for the gut microbiota under most conditions A. aegypti larvae experience in the laboratory and field.

Yin Wang, Jai Hoon Eum, Ruby E. Harrison, Luca Valzania, Xiushuai Yang, Jena A. Johnson, Derek T. Huck, Mark R. Brown, Michael R. Strand Proceedings of the National Academy of Sciences Apr 2021, 118 (15) e2101080118; DOI: 10.1073/pnas.2101080118

Whole blood and blood components from vertebrates differentially affect egg formation in three species of anautogenous mosquitoes

Donna Huber on February 24, 2021

Background: Most female mosquitoes are anautogenous and must blood feed on a vertebrate host to produce eggs. Prior studies show that the number of eggs females lay per clutch correlates with the volume of blood ingested and that protein is the most important macronutrient for egg formation. In contrast, how whole blood, blood fractions and specific blood proteins from different vertebrates affect egg formation is less clear. Since egg formation is best understood in Aedes aegypti, we examined how blood and blood components from different vertebrates affect this species and two others: the malaria vector Anopheles gambiae and arbovirus vector Culex quinquefasciatus.

Methods: Adult female mosquitoes were fed blood, blood fractions and purified major blood proteins from different vertebrate hosts. Markers of reproductive response including ovary ecdysteroidogenesis, yolk deposition into oocytes and number of mature eggs produced were measured.

Results: Ae. aegypti, An. gambiae and C. quinquefasciatus responded differently to meals of whole blood, plasma or blood cells from human, rat, chicken and turkey hosts. We observed more similarities between the anthropophiles Ae. aegypti and An. gambiae than the ornithophile C. quinquefasciatus. Focusing on Ae. aegypti, the major plasma-derived proteins (serum albumin, fibrinogen and globulins) differentially stimulated egg formation as a function of vertebrate host source. The major blood cell protein, hemoglobin, stimulated yolk deposition when from pigs but not humans, cows or sheep. Serum albumins from different vertebrates also variably affected egg formation. Bovine serum albumin (BSA) stimulated ovary ecdysteroidogenesis, but more weakly induced digestive enzyme activities than whole blood. In contrast, BSA-derived peptides and free amino acids had no stimulatory effects on ecdysteroidogenesis or yolk deposition into oocytes.

Conclusions: Whole blood, blood fractions and specific blood proteins supported egg formation in three species of anautogenous mosquitoes but specific responses varied with the vertebrate source of the blood components tested.

Harrison, R.E., Brown, M.R. & Strand, M.R. Whole blood and blood components from vertebrates differentially affect egg formation in three species of anautogenous mosquitoes. Parasites Vectors 14, 119 (2021). https://doi.org/10.1186/s13071-021-04594-9

MdBVe46 is an envelope protein that is required for virion formation by Microplitis demolitor bracovirus

Donna Huber on February 16, 2021

Bracoviruses (BVs) are endogenized nudiviruses that braconid parasitoid wasps have coopted for functions in parasitizing hosts. Microplitis demolitor is a braconid wasp that produces Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of the moth Chrysodeixis includens. Some BV core genes are homologs of genes also present in baculoviruses while others are only known from nudiviruses or other BVs. In this study, we had two main goals. The first was to separate MdBV virions into envelope and nucleocapsid fractions before proteomic analysis to identify core gene products that were preferentially associated with one fraction or the other. Results indicated that nearly all MdBV baculovirus-like gene products that were detected by our proteomic analysis had similar distributions to homologs in the occlusion-derived form of baculoviruses. Several core gene products unknown from baculoviruses were also identified as envelope or nucleocapsid components. Our second goal was to functionally characterize a core gene unknown from baculoviruses that was originally named HzNVorf64-like. Immunoblotting assays supported our proteomic data that identified HzNVorf64-like as an envelope protein. We thus renamed HzNVorf64-like as MdBVe46, which we further hypothesized was important for infection of C. includens. Knockdown of MdBVe46 by RNA interference (RNAi) greatly reduced transcript and protein abundance. Knockdown of MdBVe46 also altered virion morphogenesis, near-fully inhibited infection of C. includens, and significantly reduced the proportion of hosts that were successfully parasitized by M. demolitor.

Michael J Arvin, Ange Lorenzi, Gaelen R Burke, Michael R Strand. J Gen Virol. 2021 Feb 16. doi: 10.1099/jgv.0.001565.

Gene content evolution in the arthropods

Donna Huber on January 23, 2020

Abstract

BACKGROUND:

Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genome evolution to be addressed, even across hyper-diverse taxa within arthropods.

RESULTS:

Using 76 whole genome sequences representing 21 orders spanning more than 500 million years of arthropod evolution, we document changes in gene and protein domain content and provide temporal and phylogenetic context for interpreting these innovations. We identify many novel gene families that arose early in the evolution of arthropods and during the diversification of insects into modern orders. We reveal unexpected variation in patterns of DNA methylation across arthropods and examples of gene family and protein domain evolution coincident with the appearance of notable phenotypic and physiological adaptations such as flight, metamorphosis, sociality, and chemoperception.

CONCLUSIONS:

These analyses demonstrate how large-scale comparative genomics can provide broad new insights into the genotype to phenotype map and generate testable hypotheses about the evolution of animal diversity.

Thomas GWC, Dohmen E, Hughes DST, Murali SC, Poelchau M, Glastad K, Anstead CA, Ayoub NA, Batterham P, Bellair M, Binford GJ, Chao H, Chen YH, Childers C, Dinh H, Doddapaneni HV, Duan JJ, Dugan S, Esposito LA, Friedrich M, Garb J, Gasser RB, Goodisman MAD, Gundersen-Rindal DE, Han Y, Handler AM, Hatakeyama M, Hering L, Hunter WB, Ioannidis P, Jayaseelan JC, Kalra D, Khila A, Korhonen PK Lee CE, Lee SL, Li Y, Lindsey ARI, Mayer G, McGregor AP, McKenna DD, Misof B, Munidasa M, Munoz-Torres M, Muzny DM, Niehuis O, Osuji-Lacy N, Palli SR, Panfilio KA, Pechmann M, Perry T, Peters RS, Poynton HC, Prpic NM, Qu J, Rotenberg D, Schal C, Schoville SD, Scully ED, Skinner E, Sloan DB, Stouthamer R, Strand MR, Szucsich NU, Wijeratne A, Young ND, Zattara EE, Benoit JB, Zdobnov EM, Pfrender ME, Hackett KJ, Werren JH, Worley KC, Gibbs RA, Chipman AD, Waterhouse RM, Bornberg-Bauer E, Hahn MW, Richards S. Genome Biol. 2020 Jan 23;21(1):15. doi: 10.1186/s13059-019-1925-7.

Predaceous Toxorhynchites mosquitoes require a living gut microbiota to develop

Donna Huber on January 22, 2020

Most species of mosquitoes are detritivores that feed on decaying plant and animal materials in their aquatic environment. Studies of several detritivorous mosquito species indicate that they host relatively low diversity communities of microbes that are acquired from the environment while feeding. Our recent results also indicate that detritivorous species normally require a living gut microbiota to grow beyond the first instar. Less well known is that some mosquitoes, including those belonging to the genus Toxorhynchites, are predators that feed on other species of mosquitoes and nektonic prey. In this study, we asked whether predaceous Toxorhynchites amboinensis larvae still require living microbes in their gut in order to develop. Using the detritivorous mosquito Aedes aegypti as prey, we found that T. amboinensis larvae harbour bacterial communities that are highly similar to that of their prey. Functional assays showed that T. amboinensis first instars provided axenic (i.e. bacteria-free) prey failed to develop, while two bacterial species present in gnotobiotic (i.e. colonized by one or more known bacterial species) prey successfully colonized the T. amboinensis gut and rescued development. Axenic T. amboinensis larvae also displayed defects in growth consistent with previously identified roles for microbe-mediated gut hypoxia in nutrient acquisition and assimilation in A. aegypti. Collectively, these results support a conserved role for gut microbes in regulating the development of mosquitoes with different feeding strategies.

Kerri L. Coon, Luca Valzania, Mark R. Brown and Michael R. Strand. Proc Biol Sci. 2020 Jan 29;287(1919):20192705. doi: 10.1098/rspb.2019.2705

The genomes of two parasitic wasps that parasitize the diamondback moth

Donna Huber on November 21, 2019

Background

Parasitic insects are well-known biological control agents for arthropod pests worldwide. They are capable of regulating their host’s physiology, development and behaviour. However, many of the molecular mechanisms involved in host-parasitoid interaction remain unknown.

Results

We sequenced the genomes of two parasitic wasps (Cotesia vestalis, and Diadromus collaris) that parasitize the diamondback moth Plutella xylostella using Illumina and Pacbio sequencing platforms. Genome assembly using SOAPdenovo produced a 178 Mb draft genome for C. vestalis and a 399 Mb draft genome for D. collaris. A total set that contained 11,278 and 15,328 protein-coding genes for C. vestalis and D. collaris, respectively, were predicted using evidence (homology-based and transcriptome-based) and de novo prediction methodology. Phylogenetic analysis showed that the braconid C. vestalis and the ichneumonid D. collaris diverged approximately 124 million years ago. These two wasps exhibit gene gains and losses that in some cases reflect their shared life history as parasitic wasps and in other cases are unique to particular species. Gene families with functions in development, nutrient acquisition from hosts, and metabolism have expanded in each wasp species, while genes required for biosynthesis of some amino acids and steroids have been lost, since these nutrients can be directly obtained from the host. Both wasp species encode a relative higher number of neprilysins (NEPs) thus far reported in arthropod genomes while several genes encoding immune-related proteins and detoxification enzymes were lost in both wasp genomes.

Conclusions

We present the annotated genome sequence of two parasitic wasps C. vestalis and D. collaris, which parasitize a common host, the diamondback moth, P. xylostella. These data will provide a fundamental source for studying the mechanism of host control and will be used in parasitoid comparative genomics to study the origin and diversification of the parasitic lifestyle.

Min Shi, Zhizhi Wang, Xiqian Ye, Hongqing Xie, Fei Li, Xiaoxiao Hu, Zehua Wang, Chuanlin Yin, Yuenan Zhou, Qijuan Gu, Jiani Zou, Leqing Zhan, Yuan Yao, Jian Yang, Shujun Wei, Rongmin Hu, Dianhao Guo, Jiangyan Zhu, Yanping Wang, Jianhua Huang, Francesco Pennacchio, Michael R. Strand & Xuexin Chen. The genomes of two parasitic wasps that parasitize the diamondback moth. BMC Genomics 20, 893 (2019) doi:10.1186/s12864-019-6266-0.

Preferential infectivity of entomopathogenic nematodes in an envenomed host

Donna Huber on July 12, 2019

Entomopathogenic nematodes and parasitoid wasps are used as biological control agents for management of insect pests such as the Indian meal moth, Plodia interpunctella. The parasitoid wasp Habrobracon hebetor injects a paralytic venom into P. interpunctella larvae before laying eggs. A previous study reported that the entomopathogenic nematode Heterorhabditis indica preferentially infects P. interpunctella that have been envenomed by H. hebetor while results in this study showed a similar preference by the entomopathogenic nematode, Steinernema glaseri. We therefore tested four hypotheses for why nematode infection rates are higher in envenomed hosts: 1) elevated CO₂ emission from envenomed hosts attracts nematodes, 2) paralysis prevents hosts from escaping nematodes, 3) volatile chemicals emitted from envenomed hosts attract nematodes and increase infection, and 4) reduced immune defenses in envenomed hosts increase nematode survival. Results showed that envenomed P. interpunctella larvae emitted lower amounts of CO₂ than non-envenomed larvae. Physical immobilization of P. interpunctella larvae did not increase infection rates by S. glaseri but did increase infection rates by H. indica. Emissions from envenomed hosts were collected and analyzed by thermal desorption gas chromatography/mass spectrometry. The most abundant compound, 3-methyl-3-buten-1-ol, was found to be an effective cue for S. glaseri attraction and infection but was not an effective stimulus for H. indica. Envenomed P. interpunctellaexhibited a stronger immune response toward nematodes than non-envenomed hosts. Altogether, we conclude that different mechanisms underlie preferential infection in the two nematode species: host immobilization for H. indica and chemical cues for S. glaseri.

George N. Mbata, David I. Shapiro-Ilan, Hans T. Alborn, Michael R. Strand. Int J Parasitol. 2019 Jul 12. pii: S0020-7519(19)30168-7. doi: 10.1016/j.ijpara.2019.05.002.

Toll family members bind multiple Spätzle proteins and activate antimicrobial peptide gene expression in Drosophila

Donna Huber on May 14, 2019

This illustration depicts a dorsal view of the “common” fruit fly, or “vinegar” fly, *Drosophila melanogaster*.
Courtesy of Public Health Image Library

The Toll signaling pathway in Drosophila melanogaster regulates several immune-related functions, including the expression of antimicrobial peptide (AMP) genes. The canonical Toll receptor (Toll-1) is activated by the cytokine Spätzle (Spz-1), but Drosophila encodes eight other Toll genes and five other Spz genes whose interactions with one another and associated functions are less well understood. Here, we conducted in vitro assays in the Drosophila S2 cell line with the Toll/interleukin-1 receptor (TIR) homology domains of each Toll family member to determine if they can activate a known target of Toll-1, the promoter of the antifungal peptide gene drosomycin. All TIR family members activated the drosomycin promoter, with Toll-1 and Toll-7 TIRs producing the highest activation. We found that the Toll-1 and Toll-7 ectodomains bind Spz-1, -2, and -5 and also vesicular stomatitis virus (VSV) virions, and that Spz-1, -2, -5, and VSV all activated the promoters of drosomycin and several other AMP genes in S2 cells expressing full-length Toll-1 or Toll-7. In vivo experiments indicated that Toll-1 and Toll-7 mutants could be systemically infected with two bacterial species (Enterococcus faecalis and Pseudomonas aeruginosa), the opportunistic fungal pathogen Candida albicans and VSV with different survival in adult females and males compared with wild-type fly survival. Our results suggest that all Toll family members can activate several AMP genes. Our results further indicate that Toll-1 and Toll-7 bind multiple Spz proteins and also VSV, but differentially affect adult survival after systemic infection, potentially because of sex-specific differences in Toll-1 and Toll-7 expression.

Munmun Chowdhury, Chun-Feng Li, Zhen He, Yuzhen Lu, Xu-Sheng Liu, Yu-Feng Wang, Y. Tony Ip, Michael R. Strand and Xiao-Qiang Yu. 2019. J Biol Chem. pii: jbc.RA118.006804. doi: 10.1074/jbc.RA118.006804

What’s Bugging MICHAEL STRAND?

Donna Huber on May 13, 2019

by Leigh Beeson mosquito

When warm weather approaches, so do pesky little bloodsucking pests.

The unassuming mosquito may be smaller than a dime, but it packs a serious punch, killing more people each year than any other animal. And with average temperatures climbing around the globe, different mosquito species are making their way farther north than ever before and bringing their diseases—malaria, West Nile, dengue, and more—along for the ride.

But thanks to recent discoveries at the University of Georgia, it may soon become easier to fend off the swarm.

Regents Professor of Entomology Michael Strand’s lab found that microorganisms, or microbes, in a mosquito’s gut are essential for growth and development. Mosquito larvae spend anywhere from a few days to two weeks developing in pools of water that can be as small as an upside-down bottle cap. Microbes colonize the larvae’s digestive tracts, forming a community of microorganisms that enables the larvae to mature into adult mosquitos.

The implications of the findings could lead to new approaches for mosquito control.

“If you can disrupt their growth cycle, you could control mosquito populations,” Strand says. “Certain combinations of these organisms that exist in the digestive system of the mosquito also affect how well they are able to acquire and transmit disease-causing microorganisms to people.

Understanding how these organisms alter the mosquito’s ability to transmit diseases offers the potential for increasing resistance to certain organisms they can pass on to people.”

From a more basic science perspective, insects provide a more simplified version of a microbiome, the ecological community of microorganisms that call a space home. Researchers often discuss the roles microbiomes, such as that of the human gut, play in an individual’s health, but it’s difficult to sort through the billions of different organisms that can be present. Mosquitoes, and other insects in general, are much less complex, sometimes hosting only several hundreds of microorganisms in their digestive tracts. The smaller number of microbes make it easier for researchers to study.

“In effect, this simplicity reduces the many variables involved,” Strand says. “Some of the rules determining the importance of gut microbes in mosquito development may also have generalizable applications in how similar processes are regulated in larger animals.”

Sting like a Bee

Mosquitoes aren’t the only insects Strand studies.

His interests lie in parasitology, or how parasites interact with the animals they feed from. Parasitic wasps, comprising over a million different species, are the perfect medium to study parasite-host interactions.

Around 100 million years ago, some parasitic wasps were infected by a virus that became part of their genome. Wasps coopted that virus to deliver different types of genes into hosts.

One way wasps accomplish that is by injecting the coopted virus into other insects along with their eggs. The virus then infects the insects’ cells in much the same way as modern medicine’s gene therapies that use viruses to introduce genes into human patients for disease prevention or treatment.

The virus’ genes suppress the host insect’s immune defenses, which would otherwise destroy the foreign eggs. The wasps can then hatch and develop into adults while slowly consuming the host from the inside out.

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The article first appeared on UGA’s Great Commitments.

$1.5 million initiative to upgrade labs across campus

Donna Huber on February 18, 2019

A $1.5 million initiative to upgrade labs across campus is enabling faculty members such as Regents Professor Michael Strand to enhance their research productivity. (Photo by Dorothy Kozlowski/ UGA)

Athens, Ga. – Labs and research support spaces across campus will be getting an upgrade, thanks to a $1.5 million presidential initiative that seeks to build on the university’s dramatic growth in research activity.

Presidential renovation funds have been distributed to nine schools and colleges and will be used to upgrade labs and replace core equipment that enables faculty members to conduct research and be more competitive in seeking grant funding. Proposals were solicited from deans and chosen based on links to college and university strategic priorities, as well as implications for faculty recruitment efforts and grant funding opportunities.

“To advance the research mission of the university and attract and retain outstanding faculty, we must support state-of-the-art facilities that assist the faculty with their groundbreaking work,” said President Jere W. Morehead. “I am pleased the institution has been able to help several faculty with critical needs, thanks to this initiative.”

In the College of Agricultural and Environmental Sciences, an upgrade to an insectary that will be used to rear mosquitoes will enable Regents’ Professor and National Academy of Sciences member Michael Strand and several of his colleagues in the department of entomology to expand their research on infectious diseases such as malaria and dengue fever. “We’re going to be able to do a whole series of experiments that we currently can’t do,” Strand said, adding that the upgraded facility opens up new opportunities for grants.

Upgrades to the Sensory Evaluation and Product Development Lab in the College of Family and Consumer Sciences will enable assistant professor Ginnefer Cox to develop and evaluate new food product formulations more efficiently while also giving students hands-on experiences and facilitating industry partnerships. “This new space is going to have equipment that helps train students to be the next product developers,” Cox said. “The upgrades also create more opportunities to collaborate in research with food companies, which opens up opportunities for students to interact with them and obtain internships and permanent employment.”

In the department of physics and astronomy, part of the Franklin College of Arts and Sciences, renovation funds will aid in faculty recruitment by modernizing an outdated laboratory. “We’re really excited to have received this funding,” said department head Phillip Stancil. “The space has been unused for the last several years, and with this renovation it’ll be ready for a new experimentalist to move in.”

Other schools and colleges that have received funding through presidential renovation funds are the College of Engineering, College of Environment and Design, Odum School of Ecology, College of Public Health, College of Veterinary Medicine and the Warnell School of Forestry and Natural Resources.

Interim Senior Vice President for Academic Affairs and Provost Libby V. Morris noted that the lab renovation funds come at a time when sponsored research awards have increased by 34 percent over the past five years. It also coincides with recruitment initiatives that will bring up to 25 new faculty members to campus.

“Research activity at the University of Georgia has grown significantly in recent years, with strategic investments in faculty and facilities enabling discoveries that point the way to a healthier and more promising future,” Morris said.

Writer: Sam Fahmy, 706-583-0727, sfahmy@uga.edu

Tag: Michael Strand