我国三地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响

【目的】Wolbachia 是广泛存在于节肢动物和丝状线虫体内的一类共生菌, 能够以多种方式对宿主产生影响。精卵细胞质不亲和（CI）是其引起的最普遍的表型, 即感染Wolbachia的雄性宿主与未感染或感染不同品系的雌性宿主交配后, 不能产生后代或后代极少, 而感染同品系Wolbachia的雌雄宿主交配后则能正常产生后代。我们前期研究发现, 湖北武汉、 云南六库和天津3个地区黑腹果蝇Drosophila melanogaster被Wolbachia感染。本研究旨在明确这3个地区黑腹果蝇中Wolbachia的系统发育关系及其对宿主生殖的影响。【方法】利用Clustal X软件对Wolbachia的wsp基因序列进行比对, 利用MEGA软件构建系统发育树。采用多位点序列分型（MLST）的方法对Wolbachia进行分型。通过区内交配和区之间杂交的方式研究不同地区黑腹果蝇体内Wolbachia 的关系及其对果蝇生殖的影响。【结果】湖北武汉、 云南六库和天津3个地区黑腹果蝇中感染的Wolbachia都是属于A大组的Mel亚群。这3个地区果蝇感染的Wolbachia的序列类型（ST）不同, Wolbachia之间存在一定的差异。湖北武汉和天津果蝇中的Wolbachia能引起强烈的CI表型, 而云南六库果蝇中的Wolbachia引起的CI强度相对较弱。武汉果蝇中Wolbachia不能完全挽救天津果蝇中Wolbachia引起的CI表型, 而天津果蝇中Wolbachia也不能完全挽救武汉果蝇中Wolbachia引起的CI表型。【结论】武汉和天津地区黑腹果蝇中的Wolbachia可能距离较远。Wolbachia的长期共生可能对黑腹果蝇的进化产生了一定的影响, 湖北武汉与云南六库的黑腹果蝇中感染的Wolbachia属于不同的序列类型, 这2个地区的黑腹果蝇已发生了一定的分歧, 产生了一定的生殖隔离。

Phylogenetic analysis of Wolbachia in Drosophila melanogaster from three regions in China and their effects on host reproduction

【Aim】 Wolbachia are endosymbionts which were frequently found in arthropods and filarial nematodes. They can manipulate reproduction of their hosts by several mechanisms. Cytoplasmic incompatibility (CI) is the most common phenotype Wolbachia causes, resulting in no or few viable progenies when Wolbachia-infected males cross with uninfected females or females carrying different Wolbachia strains, while the progenies can be produced normally when males and females carrying the same Wolbachia strain cross. We previously found that Drosophila melanogaster flies collected from Wuhan of Hubei (WH), Liuku of Yunnan (LK) and Tianjin (TJ) were infected by Wolbachia. This study aims to investigate the relationships between Wolbachia in these D. melanogaster populations and their effects on host reproduction. 【Methods】 Alignments of nucleic acid homology of Wolbachia wsp genes were performed by Clustal X, and phylogenetic tree was constructed with MEGA. Sequence types (ST) of Wolbachia were analyzed using multilocus sequence typing (MLST). Crossing experiments within and between the three populations of D. melanogaster were conducted to assay CI intensity and the effect of Wolbachia on reproduction of Drosophila hosts. 【Results】 All Wolbachia in the three populations of D. melanogaster belonged to Mel group in supergroup A. MLST analysis showed different sequence types (ST) of Wolbachia in the flies from the three regions. The Wolbachia in the flies from WH and TJ could induce strong CI. Comparatively, the Wolbachia in the flies from LK expressed weaker CI. The Wolbachia in the flies from WH could not entirely rescue the CI phenotype induced by the Wolbachia in TJ flies, and vise versa. 【Conclusion】 The Wolbachia in the flies from WH might be less related with those from TJ. The long-time symbiosis of Wolbachia might affect the evolution of their Drosophila hosts. Wolbachia in WH and LK populations of D. melanogaster belong to different STs, and a definite reproductive isolation between their hosts exists.