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A Mucin2-Like Gene, NlMuc2, is Required for Early Embryonic Development in Nilaparvata lugens

  1. Research and Development Center of Rice Cropping Technology, China National Rice Research Institute, Hangzhou 311401, China; College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou 310014, China
  • Contact: FU Qiang
  • Supported by:

    This study was supported by the National Natural Science Foundation of China (Grant No. 32272538), China Agriculture Research System (Grant No. CARS-01), and the Fundamental Research Funds for Central Public Welfare Research Institute, China (Grant No. CPSIBRF-CNRRI-202406).

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Abstract:

In Nilaparvata lugens, a serious and widespread rice pest, high fecundity is one of the important reasons for large populations and outbreaks. As embryogenesis is a critical process associated with insect fecundity, this study investigated the function of the Mucin2-like gene (NlMuc2) in embryogenesis of N. lugens. The results showed that NlMuc2 was highly expressed in female reproductive organs and in 1-day-old eggs. Knockdown of NlMuc2 by RNA interference in 3rd instar nymphs resulted in increased mortality. Knockdown of NlMuc2 in 5th instar nymphs resulted in a dramatic reduction in egg hatchability from 85.9% to 24.1%, offspring numbers from 330.4 to 81.5, egg count from 382.4 to 217.0, and 86.0% of eggs with inverted embryos. Knockdown of NlMuc2 in newly emerged females resulted in retardation of ovarian development and a decrease in the number of mature eggs, with 51.0% of eggs containing inverted embryos. Transcriptome sequencing analysis of eggs revealed that numerous genes were down-regulated after NlMuc2 knockdown, with 16 and 15 down-regulated genes enriched in the Wnt and MAPK pathways, respectively. Temporal and spatial expression profiling of the selected differentially expressed genes, including Axin, Delta catenin, Glypican-4-like, and Tyrosine protein kinase transmembrane receptor Ror-like in the Wnt pathway, and MKK4 in the MAPK pathway, showed similar expression patterns to NlMuc2. Knockdown of Ror-like, Glypican-4-like, or MKK4 reduced the total number of eggs. Knockdown of Axin or MKK4 reduced the hatchability of eggs. A similar phenotype in eggs with inverted embryos was also observed in eggs laid by dsMKK4 and dsAxin. Thus, NlMuc2 is involved in embryonic development mainly by regulating the Wnt and MAPK signaling pathways. These results may provide new targets for pesticide design and RNAi-based control of N. lugens, and will also provide new insights into insect embryonic development and the function of insect mucins.

Key words: mucins, Nilaparvata lugens, embryogenesis, katatrepsis