Browsing by Author "Jiang, Xiaofang"

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    Complete Dosage Compensation in Anopheles stephensi and the Evolution of Sex-Biased Genes in Mosquitoes
    Jiang, Xiaofang; Biedler, James K.; Qi, Yumin; Hall, Andrew Brantley; Tu, Zhijian Jake (Oxford University Press, 2015-06-09)
    Complete dosage compensation refers to hyperexpression of the entire X or Z chromosome in organisms with heterogametic sex chromosomes (XYmale or ZW female) in order to compensate for having only one copy of the X or Z chromosome. Recent analyses suggest that complete dosage compensation, as in Drosophila melanogaster, may not be the norm. There has been no systematic study focusing on dosage compensation in mosquitoes. However, analysis of dosage compensation in Anopheles mosquitoes provides opportunities for evolutionary insights, as theXchromosome of Anopheles and that of its Dipteran relative,D. melanogaster formed independently from the same ancestral chromosome. Furthermore, Culicinae mosquitoes, including the Aedes genus, have homomorphic sex-determining chromosomes, negating the need for dosage compensation. Thus, Culicinae genes provide a rare phylogenetic context to investigate dosage compensation in Anopheles mosquitoes. Here, we performed RNA-seq analysis ofmale andfemale samplesof theAsian malariamosquitoAnopheles stephensiandtheyellow fevermosquitoAedes aegypti.Autosomaland X-linked genes in An. stephensi showed very similar levels of expression in both males and females, indicating complete dosage compensation. The uniformity of average expression levels of autosomal and X-linked genes remained when An. stephensi gene expression was normalized by that of their Ae. aegypti orthologs, strengthening the finding of complete dosage compensation in Anopheles. In addition,we comparatively analyzed the differentially expressed genes between adultmales and adult females in both species, investigated sex-biased gene chromosomal distribution patterns in An. stephensi and provided three examples where gene duplications may have enabled the acquisition of sex-specific expression during mosquito evolution.
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    Genomics and Transcriptomics Analysis of the Asian Malaria Mosquito Anopheles stephensi
    Jiang, Xiaofang (Virginia Tech, 2016-05-11)
    Anopheles stephensi is a potent vector of malaria throughout the Indian subcontinent and Middle East. An. stephensi is emerging as a model for molecular and genetic studies of mosquito-parasite interactions. Here we conducted a series of genomic and transcriptomic studies to improve the understanding of the biology of Anopheles stephensi and mosquito in general. First we reported the genome sequence and annotation of the Indian strain of the type form of An. stephensi. The 221 Mb genome assembly was produced using a combination of 454, Illumina, and PacBio sequencing. This hybrid assembly method was significantly better than assemblies generated from a single data source. A total of 11,789 protein-encoding genes were annotated using a combination of homology and de novo prediction. Secondly, we demonstrated the presence of complete dosage compensation in An. stephensi by determining that autosomal and X-linked genes have very similar levels of expression in both males and females. The uniformity of average expression levels of autosomal and X-linked genes remained when An. stephensi gene expression was normalized by that of their Ae. aegypti orthologs, strengthening the conclusion of complete dosage compensation in Anopheles. Lastly, we investigated trans-splicing events in Anopheles stephensi. We identified six trans-splicing events and all the trans-splicing sites are conserved and present in Ae. aegypti. The proteins encoded by the trans-spliced mRNAs are also highly conserved and their orthologs are co-linearly transcribed in out-groups of family Culicidae. This finding indicates the need to preserve the intact mRNA and protein function of the broken-up genes by trans-splicing during evolution. In summary, we presented the first genome assembly of Anopheles stephensi and studied two interesting evolution events" dosage compensation and trans-splicing - via transcriptomic analysis.
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    Insights into the Preservation of the Homomorphic Sex-Determining Chromosome of Aedes aegypti from the Discovery of a Male-Biased Gene Tightly Linked to the M-Locus
    Hall, Andrew Brantley; Timoshevskiy, Vladimir A.; Sharakhova, Maria V.; Jiang, Xiaofang; Basu, Sanjay; Anderson, Michelle A. E.; Hu, Wanqi; Sharakhov, Igor V.; Adelman, Zach N.; Tu, Zhijian Jake (Oxford University Press, 2014-01-01)
    The preservation of a homomorphic sex-determining chromosome in some organisms without transformation into a heteromorphic sex chromosome is a long-standing enigma in evolutionary biology. A dominant sex-determining locus (or M-locus) in an undifferentiated homomorphic chromosome confers the male phenotype in the yellow fever mosquito Aedes aegypti. Genetic evidence suggests that the M-locus is in a nonrecombining region. However, the molecular nature of the M-locus has not been characterized. Using a recently developed approach based on Illumina sequencing of male and female genomic DNA, we identified a novel gene, myo-sex, that is present almost exclusively in the male genome but can sporadically be found in the female genome due to recombination. For simplicity, we define sequences that are primarily found in the male genome as male-biased. Fluorescence in situ hybridization (FISH) on A. aegypti chromosomes demonstrated that the myo-sex probe localized to region 1q21, the established location of theM-locus.Myo-sex is a duplicated myosin heavy chain gene that is highly expressed in the pupa and adult male.Myo-sex shares 83% nucleotide identity and 97% amino acid identity with its closest autosomal paralog, consistent with ancient duplication followed by strong purifying selection. Compared with males, myo-sex is expressed at very low levels in the females that acquired it, indicating that myo-sexmay be sexually antagonistic. This study establishes a framework to discover male-biased sequences within a homomorphic sex-determining chromosome and offers new insights into the evolutionary forces that have impeded the expansion of the nonrecombining M-locus in A. aegypti.
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    Integrated proteomic and transcriptomic analysis of the Aedes aegypti eggshell
    Marinotti, Osvaldo; Ngo, Tuan; Kojin, Bianca B.; Chou, Shao-Pei; Nguyen, Brian; Juhn, Jennifer; Carballar-Lejarazú, Rebeca; Marinotti, Pedro N.; Jiang, Xiaofang; Walter, Marika F.; Tu, Zhijian Jake; Gershon, Paul D.; James, Anthony A. (2014-04-05)
    Background Mosquito eggshells show remarkable diversity in physical properties and structure consistent with adaptations to the wide variety of environments exploited by these insects. We applied proteomic, transcriptomic, and hybridization in situ techniques to identify gene products and pathways that participate in the assembly of the Aedes aegypti eggshell. Aedes aegypti population density is low during cold and dry seasons and increases immediately after rainfall. The survival of embryos through unfavorable periods is a key factor in the persistence of their populations. The work described here supports integrated vector control approaches that target eggshell formation and result in Ae. aegypti drought-intolerant phenotypes for public health initiatives directed to reduce mosquito-borne diseases. Results A total of 130 proteins were identified from the combined mass spectrometric analyses of eggshell preparations. Conclusions Classification of proteins according to their known and putative functions revealed the complexity of the eggshell structure. Three novel Ae. aegypti vitelline membrane proteins were discovered. Odorant-binding and cysteine-rich proteins that may be structural components of the eggshell were identified. Enzymes with peroxidase, laccase and phenoloxidase activities also were identified, and their likely involvements in cross-linking reactions that stabilize the eggshell structure are discussed.
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    Integrating transcriptomic and proteomic data for accurate assembly and annotation of genomes
    Prasad, T. S. Keshava; Mohanty, Ajeet Kumar; Kumar, Manish; Sreenivasamurthy, Sreelakshmi K.; Dey, Gourav; Nirujogi, Raja Sekhar; Pinto, Sneha M.; Madugundu, Anil K.; Pati, Arun H.; Advani, Jayshree; Manda, Srikanth S.; Gupta, Manoj Kumar; Dwivedi, Sutopa B.; Kelkar, Dhanashree S.; Hall, Brantley; Jiang, Xiaofang; Peery, Ashley; Rajagopalan, Pavithra; Yelamanchi, Soujanya D.; Solanki, Hitendra S.; Raja, Remya; Sathe, Gajanan J.; Chavan, Sandip; Verma, Renu; Patel, Krishna M.; Jain, Ankit P.; Syed, Nazia; Datta, Keshava K.; Khan, Aafaque Ahmed; Dammalli, Manjunath; Jayaram, Savita; Radhakrishnan, Aneesha; Mitchell, Christopher J.; Na, Chan-Hyun; Kumar, Nirbhay; Sinnis, Photini; Sharakhov, Igor V.; Wang, Charles; Gowda, Harsha; Tu, Zhijian Jake; Kumar, Ashwani; Pandey, Akhilesh (2017-01)
    Complementing genome sequence with deep transcriptome and proteome data could enable more accurate assembly and annotation of newly sequenced genomes. Here, we provide a proof-of-concept of an integrated approach for analysis of the genome and proteome of Anopheles stephensi, which is one of the most important vectors of the malaria parasite. To achieve broad coverage of genes, we carried out transcriptome sequencing and deep proteome profiling of multiple anatomically distinct sites. Based on transcriptomic data alone, we identified and corrected 535 events of incomplete genome assembly involving 1196 scaffolds and 868 protein-coding gene models. This proteogenomic approach enabled us to add 365 genes that were missed during genome annotation and identify 917 gene correction events through discovery of 151 novel exons, 297 protein extensions, 231 exon extensions,192 novel protein start sites,19 novel translational frames, 28 events of joining of exons, and 76 events of joining of adjacent genes as a single gene. Incorporation of proteomic evidence allowed us to change the designation of more than 87 predicted "noncoding RNAs" to conventional mRNAs coded by protein-coding genes. Importantly, extension of the newly corrected genome assemblies and gene models to 15 other newly assembled Anopheline genomes led to the discovery of a large number of apparent discrepancies in assembly and annotation of these genomes. Our data provide a framework for how future genome sequencing efforts should incorporate transcriptomic and proteomic analysis in combination with simultaneous manual curation to achieve near complete assembly and accurate annotation of genomes.
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    The Physical Genome Mapping of Anopheles albimanus Corrected Scaffold Misassemblies and Identified Interarm Rearrangements in Genus Anopheles
    Artemov, Gleb N.; Peery, Ashley N.; Jiang, Xiaofang; Tu, Zhijian Jake; Stegniy, Vladimir N.; Sharakhova, Maria V.; Sharakhov, Igor V. (Genetics Society of America, 2017-01-01)
    The genome of the Neotropical malaria vector Anopheles albimanus was sequenced as part of the 16 Anopheles Genomes Project published in 2015. The draft assembly of this species consisted of 204 scaffolds with an N50 scaffold size of 18.1 Mb and a total assembly size of 170.5 Mb. It was among the smallest genomes with the longest scaffolds in the 16 Anopheles species cluster, making An. albimanus the logical choice for anchoring the genome assembly to chromosomes. In this study, we developed a high-resolution cytogenetic photomap with completely straightened polytene chromosomes from the salivary glands of the mosquito larvae. Based on this photomap, we constructed a chromosome-based genome assembly using fluorescent in situ hybridization of PCR-amplified DNA probes. Our physical mapping, assisted by an ortholog-based bioinformatics approach, identified and corrected nine misassemblies in five large genomic scaffolds.Misassemblies mostly occurred in junctions between contigs. Our comparative analysis of scaffolds with the An. gambiae genome detected multiple genetic exchanges between pericentromeric regions of chromosomal arms caused by partial-arm translocations. The finalmap consists of 40 ordered genomic scaffolds and corrected fragments ofmisassembled scaffolds. The An. albimanus physical map comprises 98.2% of the total genome assembly and represents the most complete genome map among mosquito species. This study demonstrates that physical mapping is a powerful tool for correcting errors in draft genome assemblies and for creating chromosome-anchored reference genomes.