温度通过影响Wolbachia滴度调控赤眼蜂生殖方式

Temperature regulates the reproduction mode of Trichogramma embryophagum( Hymenoptera: Trichogrammatidae ) by influencing the titer of endosymbiont Wolbachia

【目的】揭示温度对宿主体内Wolbachia滴度及其调控宿主生殖作用的影响。【方法】以感染Wolbachia且营孤雌产雌生殖的食胚赤眼蜂Trichogramma embryophagum为对象,在22,25,28和31℃4个梯度温度下连续培养5代,观察生殖方式、性比等生物学特性;采用实时荧光定量PCR以Wolbachia特异基因——外膜蛋白基因(wsp)、二磷酸果糖醛缩酶基因(fbp A)和酰胺转移酶基因(gat B)为靶标对内生菌进行定量分析。【结果】22和25℃条件下连续培养5代,食胚赤眼蜂生殖方式均未发生改变(无雄蜂出现),且5代赤眼蜂群体Wolbachia滴度没有明显差异;28℃下,食胚赤眼蜂在F3代开始有雄蜂出现,至F5代雄蜂比例明显增多,且体内Wolbachia滴度在F2代开始下降,至F5代显著下降;31℃下,F2代即有雄蜂出现,至F5代已经恢复成产雄孤雌生殖,体内Wolbachia滴度也在F2代开始下降,F3代开始显著降低,到F5代Wolbachia滴度极小甚至检测不到。【结论】高温可改变营孤雌产雌生殖赤眼蜂的生殖方式及体内Wolbachia滴度,且随着处理代数的增加以及温度的升高作用显著,即高温对营孤雌产雌生殖赤眼蜂生殖方式改变程度与其体内Wolbachia滴度呈负相关。

【Aim】To reveal the effect of temperature on Wolbachia titer and its function in regulating the biological characteristics of host,the relationship between the biological indices of host and Wolbachia titer at different temperatures was evaluated in this study. 【Methods 】 Trichogramma embryophagum wasps infected by parthenogenesis-inducing Wolbachia were cultivated under four temperature gradients（ 22,25,28 and 31℃） for five consecutive generations,and the biological characteristics including the reproductive mode and sex ratio were observed. At the same time,the Wolbachia titer was detected by fluorescence quantitative real-time PCR,using the specific primers of the outer surface protein gene（ wsp）,fructose bisphosphate aldolase gene（ fbp A） and glutamyl-tRNA（ Gln） amidotransferase subunit B gene（ gat B） in Wolbachia. 【Results 】 At 22 and 25℃,the reproduction mode of the total five generations of T. embryophagum was not altered,without drones appearing in culture population,and the Wolbachia titer also was not significantly different among five generations. At 28℃,a few of drones were found in F3 generation and the majority of drones appeared in F5 generation significantly,while the Wolbachia titer in T. embryophagum began to decline in F2 generation and decreased significantly till F5 generation. At 31℃,in F2 generation the drones appeared,and in F5 generation all T. embryophagum had restored to the androgenetic parthenogenetic; the Wolbachia titer began to decrease in the F2 generation,decreased significantly in F3 generation and was not detectable by PCR in F5 generation.【Conclusion】The reproduction mode and Wolbachia titer in parthenogenetic thelytokous Trichogramma can be altered by high temperature,and are affected significantly with the increase of temperature and generation. In other words,the alteration degree of reproductive mode of Trichogramma due to high temperature is negatively correlated with the endoymbiont Wolbachia titer.