| Wolbachia is a Gram negative intracellular symbiotic bacterium that is matrilineally inherited and exists in various arthropods.Wolbachia promotes its transmission and stable existence in the host population through reproductive regulation of the host.Wolbachia is also known as a reproductive symbiotic bacterium by scholars due to its reproductive regulatory role.Its main effects include cytoplasmic incompatibility(CI),parthenogenesis induction(PI),male killing and feminization.Wolbachia can be stably transmitted to offspring through vertical transmission in the host,but the stability of Wolbachia may change due to adverse environmental conditions such as high temperature treatment,ultraviolet radiation,etc.WO phage is a virus present in the Wolbachia genome,which not only carries genetic factors closely related to Wolbachia induced CI,but also is an important factor affecting Wolbachia stability.Research has shown that WO phage can respond to the effects of different environmental factors(nutritional pressure,temperature,etc.)by changing their proliferation mode(lytic and lysogenic),thereby changing their relationship with Wolbachia.In addition,studies have shown that Wolbachia infection can also affect the stress resistance of host insects.Therefore,studying the stability effects of different stress treatments on Wolbachia not only helps to better understand the mechanism of Wolbachia’s induced reproductive regulation,but also provides theoretical basis for better evaluating its potential as a biological control factor for important pests.Thaia rubiginosa Kuoh belongs to the family Cicadaidae in the order Hemiptera,and is one of the important pests of rice.It occurs more severely in the rice region of southwestern China.According to the previous research results in the laboratory,some individuals of Thaia rubiginosa in the natural population can detect Wolbachia infection,and preliminary genetic hybridization experiments indicate that Wolbachia can cause the host to produce CI phenomenon.In order to further clarify the actual infection of Wolbachia in different natural populations of Thaia rubiginosa,the efficiency of vertical transmission and the factors affecting the stability of the Wolbachia strain,this study examined the infection of Wolbachia and WO phage in different geographical populations of Thaia rubiginosa,Explored the dynamic relationship between Wolbachia and WO phage under normal and suitable conditions and stress conditions,as well as their impact on host reproductive regulation.The main research content and results are as follows:1 Study on the relationship between Wolbachia and WO phage in the body of Thaia rubiginosaThrough the detection of the infection of Wolbachia and WO phage in different geographical populations of Thaia rubiginosa in Chongqing,we found that individuals in the four collected geographical populations of Thaia rubiginosa were able to detect the presence of Wolbachia and WO phage,but the infection rates of each population varied significantly,with the highest infection rate of 100% and the lowest infection rate of only 5%.Through indoor rearing of Thaia rubiginosa(5 generations)and generation by generation detection of Wolbachia infection in its offspring,it was found that its vertical transmission efficiency in the host reached 100%,indicating that the Wolbachia strain can stably inherit in the host.The detection of infection in different tissues of Thaia rubiginosa showed that Wolbachia was distributed in the head,chest,abdomen,feet,and wings of Thaia rubiginosa,with a higher content in the abdomen and chest,and a lower content in the head,feet,and wings.Through the detection of Wolbachia bacteria in the body of Thaia rubiginosa at different days of age,we found that the bacteria amount in the early stage increased with the increase of its age,reaching the maximum value at 13 days of age,and then began to decline.Moreover,the Wolbachia bacteria amount in the female adult of Thaia rubiginosa was significantly more than that in the male adult.The results showed that the content of Wolbachia in the body of Thaia rubiginosa was significantly related to the gender and age of Thaia rubiginosa.In addition,the variation trend of WO phage content with age is basically consistent with that of Wolbachia,and the correlation analysis results indicate that there is a positive correlation between the content of both,indicating that the WO phage carried by Wolbachia is a lysogenic bacteriophage that replicates with the replication of the host Wolbachia.2 Study on the effect of stress on the stability of Wolbachia and WO Phage infected by Thaia rubiginosaThe results of starvation and temperature stress studies on the 3-day old adults of Thaia rubiginosa showed that starvation stress had a small impact on the stability of Wolbachia and WO phage in Thaia rubiginosa,and the content of Wolbachia and WO phage had no significant difference compared to normal treatment,and the change trend of their content was still consistent.However,temperature stress has a significant impact on the stability of Wolbachia and WO phage in Thaia rubiginosa.Compared to the appropriate temperature,the content of Wolbachia in the body of Thaia rubiginosa significantly decreased after high-temperature treatment at 32℃,while the content of WO phage increased significantly compared to normal treatment,with a reverse trend of change,indicating a negative correlation between the content of Wolbachia and WO phage.Overall,starvation treatment did not affect the transformation of the properties of WO phage,which remained lysogenic in the host;After high-temperature treatment,the content of WO phage will significantly increase,indicating that WO phage may have converted to lytic bacteriophages at this time.3 Study on the effect of Wolbachia on Cytoplasmic Incompatibility of Thaia rubiginosaFirst of all,we found through genetic hybridization experiments that the hatchability of hybrid combinations of infected and uninfected Wolbachia males was significantly lower than that of both uninfected Wolbachia females and males,indicating that Wolbachia strains infected in the body of Thaia rubiginosa can induce cytoplasmic incompatibility.In addition,male adults with higher Wolbachia content(different day ages)of Thaia rubiginosa can induce higher intensity of CI action,causing the eggs of their offspring to fail to hatch normally.However,when the female of Thaia rubiginosa also infects Wolbachia of the same strain,the hatching rate of the hybrid combination eggs significantly increases,indicating that female infection with Wolbachia of the same strain has a rescue effect on CI induced by male infection.Secondly,treatment at 32℃ under high temperature,it was found that under 32℃,the hatching rate of the mating group of female and male adults of Thaia rubiginosa significantly decreased compared to the normal group,indicating that high temperature also had a negative impact on the reproductive activity of Thaia rubiginosa.However,the hatching rate of the male worm infected with Wolbachia and the uninfected female worm mating group at 32℃ was lower than that of both the uninfected female and male adult worm mating groups,indicating that both high temperature and CI induced by Wolbachia male worm infection had a negative impact on the reproductive activity of Thaia rubiginosa,resulting in a lower hatching rate. |
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