擬黃果蠅性別比減數分裂驅動之轉錄體學分析

Transcriptomic Analyses of Sex-ratio Meiotic Drive in Drosophila simulans

林頌雅(Sung-Ya Lin)

指導教授 ： 丁照棣

國立臺灣大學/生命科學院/基因體與系統生物學學位學程/碩士(2018年)

https://doi.org/10.6342/NTU201803419

摘要

性別比 (sex-ratio, SR)減數分裂驅動會讓X染色體比Y染色體更容易被傳到下一代，因此造成偏向產生雌性的子代。SR減數分裂驅動曾經在不同的物種中被發現過，但我們對於造成這個現象的分子機制還是不甚瞭解。在擬黃果蠅 (Drosophila simulans)的巴黎SR系統中，有很多參與作用的基因，但至今只有HP1基因家族裡的HP1D2是被確認的。HP1D2在SR品系中有一段chromo shadow domain的缺失，並且表現量較野生型標準品系(ST)低。為了調查HP1D2的基因型和SR現象的關聯性，我做了基因型鑑定，並發現在ST品系內和SR品系內都有基因型差異。這項結果代表只有HP1D2基因型並無法預測SR的現象。為了更系統性地發現其他與SR相關的基因，我比較了ST與SR品系果蠅在精巢基因表現的轉錄體差異。在這些基因之中，有很高比例的多細胞生物生殖與免疫反應相關的基因。我接著做RT-qPCR來確認SR候選基因中的34個基因。雖然有五個基因在三個SR品系中都有較高表現量，包括CG16772、CG15209、Ser7、CG34265和CG43348，但其他有表現差異的基因在不同SR品系中都不同。SR品系的機制和遺傳基礎可能是不一樣的。依照現有的結果，要區分主要機制是殺手-目標驅動 (killer-target drive)或毒藥-解毒劑驅動 (poison-antidote drive)還很困難，但殺手-目標驅動是跟目前結果比較吻合的。如果可以找到Y染色體上的目標，就有可能闡明巴黎SR系統的機制。

關鍵字

性別比 ； 減數分裂驅動 ； 轉錄體 ； 擬黃果蠅 ； HP1D2

並列摘要

Sex-ratio (SR) meiotic drives, favoring the transmission of X over Y chromosome, lead to strong female-biased progeny of affected males. SR meiotic drives have been reported in several independent lineages. Yet, the molecular mechanism remains largely unclear. In Drosophila simulans, it has been known that many genes are involved in the Paris SR system, but only HP1D2, a member of the Heterochromatin Protein 1 (HP1) gene family, was identified. HP1D2 possesses a deletion of chromo shadow domain in SR strains and is expressed at lower level in SR relative to wild-type standard (ST) strains. To examine the correlation between the HP1D2 genotype and the SR phenotype, genotyping was performed. The observation of variation of HP1D2 in both ST and SR strains indicates that the genotypes alone cannot predict SR phenotypes. To systematically identify other SR-related genes, the transcriptomic differences of testicular expression between three ST and three SR strains were compared. Among these genes, they are highly enriched in genes associated with multicellular organism reproduction and immune response. The RT-qPCR analysis was then performed to validate 34 genes from the SR candidate genes. Although five genes, namely CG16772, CG15209, Ser7, CG34265, and CG43348, were consistently up-regulated in three SR strains, other differentially expressed genes differed among these strains. The underlying mechanisms and genetic bases of SR strains may be different. Based on the current results, although it is still difficult to distinguish major mechanisms, the killer-target drive or the poison-antidote drive, the killer-target drive is more consistent with the current results. If the target on Y chromosome can be identified, it is possible to elucidate the underlying mechanism of the Paris SR system.

並列關鍵字

sex ratio ； meiotic drive ； transcriptome ； Drosophila simulans ； HP1D2

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