On November 26, 2021, the plant virus vector insect team of Academician Chen Jianping/Zhang Chuanxi/Li Junmin of Ningbo University published a research paper entitled "A feminizingswitchin a hemimetabolous insect" online on Science Advances. The paper reported that Nlfmd and its ligand protein Nlfmd2, a factor involved in the determination of females of brown planthoppers, were reported, and the complex NlFMD/NlFMD2 was verified in vitro to regulate the development of female-specific female planthopper females by binding to the repeating element (G/A) AAGAA on the female intersex gene 4, thereby regulating the development of brown planthopper females.
Sex differentiation is the process of female or male-specific development of germ cells on the basis of sex determination. Insects are the most diverse group in the biological world, with complex and diverse reproductive patterns, while at the same time evolving complex and delicate mechanisms for determining sex. The Doublesex gene is considered to be the most conservative link in the insect sex determination pathway, and the upstream gene achieves sex-specific development by regulating the male-female variable splicing of Doublesex, but the molecular mechanism of Doublesexpre-mRNA regulation can refer to a single model (from Drosophila nigricans), and whether the regulatory patterns of other insects are completely consistent with those of Drosophila are of great significance to the study of insect sex determination.
Hemiptera is an evolutionarily older group of insects relative to diptera and is a taxa with a high number of pests that harm food crops. Combining the research results of the pre-brown planthopper genome and transcriptome, the research team conducted large-scale RNAi screening of the early genes of the brown planthopper embryo, and successfully found two new genes, Nlfmd and Nlfmd2, which were involved in regulating Doublesex's variable splicing. After knocking out Nlfmd and Nlfmd2 at the nymph stage, male-specific Doublesex expression appeared in the female, and the brown planthopper appeared phenotype of male and female chimeras after feathering, while the researchers demonstrated through protein interaction experiments that Nlfmd and Nlfmd2 could form complexes. The team successfully simulated female-specific and male-specific variable splicing in the 293T cell line by constructing an artificial Doublesexmini-genome in vitro. After expressing Nlfmd and Nlfmd2 in 293T cell lines, female variable splicing patterns increase in Doublesexpre-mRNA variable splicing. Further studies have shown that after the spot mutation of the repeat sequence (G/A) AAGAA on female-specific exon 4, the regulatory effect disappeared, and the results were verified by microthermophoretic molecular interaction experiments. This study identified two new genes Nlfmd and Nlfmd2 involved in sex determination, and preliminarily demonstrated the molecular mechanism of the Nmld/Nlfmd2 complex regulating Doublesex, indicating that the regulation of variable splices in Doublesex also has species diversity. Rice planthopper is the most harmful pest in China and an important vector insect for spreading rice virus, and this research result will provide an important basis for the future use of sterile insect technology to control brown planthoppers.
The first author of the paper is Dr. Zhuo Jichong of Ningbo University, and the doctoral students of Zhejiang University, Zhang Houhong and Hu Qingling, are the co-first authors. Academician Chen Jianping of Ningbo University, Researcher Li Junmin, Professor Zhang Chuanxi and Professor Tu Zhijian of Virginia Tech University are co-corresponding authors. Dr. Lu Jiabao, Huang Haijian, Lu Gang of Ningbo University, graduate students Zhang Yan and Wang Haiqiang, Dr. Zhang Jinli of Zhejiang University and graduate students Li Hanjing, Xie Yucheng and Wang Weiwei also participated in some of the research work. The research project was funded by the National Natural Science Foundation of China and the China Postdoctoral Science Foundation.
Thesis Link:
https://www.science.org/doi/10.1126/sciadv.abf9237
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