Kotsyfakis Michalis, Kopáček Petr, Franta Zdeněk, Pedra Joao H F, Ribeiro José M C
Institute of Parasitology, Biology Center of the Czech Academy of Sciences, Budweis, Czech Republic.
Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America.
PLoS Negl Trop Dis. 2015 May 13;9(5):e0003754. doi: 10.1371/journal.pntd.0003754. eCollection 2015 May.
Ixodes ricinus is the main tick vector of the microbes that cause Lyme disease and tick-borne encephalitis in Europe. Pathogens transmitted by ticks have to overcome innate immunity barriers present in tick tissues, including midgut, salivary glands epithelia and the hemocoel. Molecularly, invertebrate immunity is initiated when pathogen recognition molecules trigger serum or cellular signalling cascades leading to the production of antimicrobials, pathogen opsonization and phagocytosis. We presently aimed at identifying hemocyte transcripts from semi-engorged female I. ricinus ticks by mass sequencing a hemocyte cDNA library and annotating immune-related transcripts based on their hemocyte abundance as well as their ubiquitous distribution.
METHODOLOGY/PRINCIPAL FINDINGS: De novo assembly of 926,596 pyrosequence reads plus 49,328,982 Illumina reads (148 nt length) from a hemocyte library, together with over 189 million Illumina reads from salivary gland and midgut libraries, generated 15,716 extracted coding sequences (CDS); these are displayed in an annotated hyperlinked spreadsheet format. Read mapping allowed the identification and annotation of tissue-enriched transcripts. A total of 327 transcripts were found significantly over expressed in the hemocyte libraries, including those coding for scavenger receptors, antimicrobial peptides, pathogen recognition proteins, proteases and protease inhibitors. Vitellogenin and lipid metabolism transcription enrichment suggests fat body components. We additionally annotated ubiquitously distributed transcripts associated with immune function, including immune-associated signal transduction proteins and transcription factors, including the STAT transcription factor.
CONCLUSIONS/SIGNIFICANCE: This is the first systems biology approach to describe the genes expressed in the haemocytes of this neglected disease vector. A total of 2,860 coding sequences were deposited to GenBank, increasing to 27,547 the number so far deposited by our previous transcriptome studies that serves as a discovery platform for studies with I. ricinus biochemistry and physiology.
蓖麻硬蜱是在欧洲传播导致莱姆病和蜱传脑炎的微生物的主要蜱类媒介。蜱传播的病原体必须克服蜱组织中存在的先天免疫屏障，包括中肠、唾液腺上皮和血腔。在分子层面，当病原体识别分子触发血清或细胞信号级联反应，从而导致抗菌物质的产生、病原体调理作用和吞噬作用时，无脊椎动物的免疫反应就会启动。我们目前旨在通过对血细胞cDNA文库进行大规模测序，并根据其在血细胞中的丰度及其普遍分布来注释免疫相关转录本，从而鉴定半饱血雌性蓖麻硬蜱的血细胞转录本。
方法/主要发现：对来自血细胞文库的926,596条焦磷酸测序读数和49,328,982条Illumina读数（长度为148 nt）进行从头组装，再加上来自唾液腺和中肠文库的超过1.89亿条Illumina读数，生成了15,716条提取的编码序列（CDS）；这些序列以带注释的超链接电子表格形式显示。读数映射允许鉴定和注释组织富集转录本。在血细胞文库中总共发现327个转录本显著过度表达，包括那些编码清道夫受体、抗菌肽、病原体识别蛋白、蛋白酶和蛋白酶抑制剂的转录本。卵黄蛋白原和脂质代谢转录本的富集表明存在脂肪体成分。我们还注释了与免疫功能相关的普遍分布的转录本，包括免疫相关信号转导蛋白和转录因子，包括STAT转录因子。
结论/意义：这是首次采用系统生物学方法来描述这种被忽视的疾病媒介血细胞中表达的基因。总共2860条编码序列已存入GenBank，使我们之前转录组研究存入的序列数量增加到27547条，为蓖麻硬蜱生物化学和生理学研究提供了一个发现平台。
