A collaborative research team led by Xi Chen and Chen-Yu Zhang at Nanjing University and Ningjia He at Southwest University has made a significant discovery in a recent publication in Insect Science. The team found that mulberry microRNAs (miRNAs) can regulate the development and cocooning of silkworms through a cross-kingdom manner. This discovery provides a new clue to understanding the intricate process of co-evolution between silkworms and mulberry plants.
Silkworms feed exclusively on mulberry leaves, however, the molecular basis for this feeding preference, as well as the interaction mechanisms between mulberry and silkworms, remain largely unknown. Recent studies have uncovered a previously unrecognized role for plant miRNAs as environmental determinants of animal development and health. In detail, plant-derived miRNAs in food sources can be absorbed by mammals and insects through dietary intake, actively influencing gene expression and phenotypic outcomes in recipient mammals and insects. This cross-kingdom regulatory mechanism motivates the hypothesis that dietary mulberry miRNAs may contribute to silkworm's feeding preference on mulberry leaves. In this study, the authors demonstrated that mulberry miRNAs were present in silkworms through oxidized sRNA sequencing, quantitative RT-PCR and Northern blotting. Further, through feeding silkworms with an artificial diet supplemented with synthetic miRNAs or fresh mulberry leaves supplemented with miRNA antisenses, they showed that mulberry miRNAs can be ingested by silkworms and accumulated in hemolymph and tissues, which further reprogram gene expression and reshape silkworm phenotypes.
The scientific significance of this study is highlighted below:
(1) This study reveals a previously uncharacterized role for the miRNA component instead of proteins and secondary metabolites in mulberry leaves to influence silkworm development. The theories about the feeding preference of silkworms need to be re-examined from a new angle besides the traditional focus on proteins and secondary metabolites of mulberry leaves.
(2) This study provides additional support for the concept of horizontal miRNA transfer across species and kingdoms. Ingested mulberry miRNAs can even reshape the developmental fate and phenotypic outcomes of silkworms. These findings may provide new insights into the mechanisms underlying horizontal miRNA transfer and offer valuable hints for understanding of plant-animal interaction.
(3) In an evolutionary sense, the role of mulberry miRNAs in regulating silkworm phenotypes may offer valuable hints for our understanding of co-evolution. From this standpoint, mulberry leaves might not be accidentally supplied as the food source for domesticated silkworm but instead selected with specific purpose, probably for their promotive effects on silkworm growth and cocooning.
Zhou et al. Cross-kingdom regulation of silkworm development and cocooning by mulberry microRNAs. Insect Science. https://doi.org/10.1111/1744-7917.13424
