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Progress in Cytoplasmic Incompatibility - achieving manual manipulation

 Research

On March 25, 2022, professor Zefang Wang’s team from the School of Life Sciences, Tianjin University published a paper in Nature Communications titled "Crystal Structures of Wolbachia CidA and CidB Reveal Determinants of Bacteria-induced Cytoplasmic Incompatibility and Rescue", reporting the artificial manipulation achievement of cytoplasmic incompatibility (CI) by designing CI factors from Wolbachia.

This CI phenomenon, originally triggered by bacteria, was used to control mosquito populations for the purpose of controlling insect-borne diseases. This research is another important development in the field of anti-mosquito-borne diseases research, following the recent discovery of the molecular mechanism of CI (see PNAS|Understanding the molecular mechanism of “sterility” in mosquitoes using bacteria).

Wolbachia can induce CI in the union of amphoteric gamete, resulting in “sterility” of mosquitoes. Based on this theory, the biological method of controlling mosquito populations can be highly efficient and green and the spread of mosquito-borne diseases such as dengue fever and Zika around the world can be efficiently controlled. According to the data announced by National Environment Agency of Singapore in July 2021, the number of mosquitoes in areas where Wolbachia-infected male mosquitoes were released was reduced by 98% compared to non-released areas, and the outbreak of dengue fever was reduced by 88% (https://www.nea.gov.sg). CI is caused by two interrelated proteins called CI factor A (CifA) and CI factor B (CifB). In the previous study, the joint research team found that interactions between CI factors are a key factor in the production of CI inWolbachia(Xiao et al., PNAS, 2021). Accordingly, the team proposed a new idea: could the CI phenomenon be controlled by manipulating the interactions of CI factors? This would provide an important tool for designing novel CI factors to control mosquito-borne virus transmission more effectively.

To test the idea above, the research team performed a comprehensive structural, biochemical and functional study of CI factors from two different Wolbachia strains (wPip,wMel) reported in this article published in Nature Communications. These factors were named Cid (including CidAwMel-CidBwMel, CidAwPip-CidBwPip) due to the deubiquitylase activity of CifB. The research team first resolved the structures of the complexes of the two different types of CI factors using crystallography and AlphaFold predictions (Figure 1a-b). Based on the structural analysis, they artificially modified wild-type CidAwMelby replacing the amino acid responsible for the interaction with CidBwMelwith the corresponding region from another strain of CidAwPipto obtain an artificial chimeric protein named CidAwMel(ST). In subsequent functional tests, CidAwMel(ST) did interact with CidBwPipfrom a different strain and was able to rescue the CidBwPip-induced growth defect in yeast (Figure 1c-d), in accordance with the expected results. They also found that if the artificial chimeric protein CidAwMel(ST) interaction interface amino acids were revertantly mutated separately (to obtain CidAwMel(ST-1) ~ CidAwMel(ST-9)), CidAwMel(ST-4)/ CidAwMel(ST-7)/ CidAwMel(ST-9) could not interact with CidBwPipand could not rescue CidBwPip-induced growth defects in yeast (Figure 1d), indicating that these regions play a critical role for CidAwMel(ST)-CidBwPipbinding. Finally, the team successfully resolved the structure of the CidAwMel(ST)-CidBwPipND1-ND2complex, confirming the contribution of the artificially designed CI factor-interacting interface amino acids to the binding specificity (Figure 1e).

The study above achieved the first artificial manipulation of CI by artificially designing CI factors and regulating their interactions, which also has important implications for the future use of Wolbachia and CI in the prevention and control of mosquito-borne diseases and agricultural pests.

Haofeng Wang (PhD candidate of the School of Life Sciences, Tianjin University), Yunjie Xiao (postdoc in the School of Life Sciences, Tianjin University) and Xia Chen (PhD of the School of Life Sciences, Tianjin University) are the joint first authors of this paper. Professor Zefang Wang from the School of Life Sciences, Tianjin University is one of the co-corresponding authors of this research paper.Tianjin University is the unit of first correspondent of this paper. The participating institutions are Shanghai Tech University, Chongqing Medical University, Yale University, Shanghai Jiao Tong University and Nanjing University. Crystal diffraction data collection was assisted by the Shanghai Synchrotron Radiation Facility and National Center for Protein Science Shanghai. This research was supported by the National Basic Research Program of China, the National Natural Science Foundation of China, and the Tianjin Funds for Distinguished Young Scientists.

The original article is linked below

https://www.nature.com/articles/s41467-022-29273-w 



Fig. 1 Artificially designed CI factors manipulate CI generation and rescue.a3D structure of CidAwPip(Tunis)-CidBwPip(Tunis)ND1-ND2complex.bModel of CidAwMel-CidBwMelND1-ND2complex predicted by Alphafold.cThe artificial chimeric protein CidAwMel(ST) can interact with CidBwPipfrom different strains. Revertant mutation of the interface amino acid makes the mutant protein unable to interact with CidBwPip, and regions 4, 7 and 9 play an important role in binding.dThe artificial chimeric protein CidAwMel(ST) canrescue the CidBwPip-induced growth defects in yeast.e3D structure ofCidAwMel(ST) -CidBwPip(Pel)ND1-ND2compelx.

By School of Life Sciences

Editor: Sun Xiaofang

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