Author: Meiling Yang, Institute of Zoology, Chinese Academy of Sciences
Competing Interests: Meiling Yang is an author of the article discussed in this blog.
Image Credit: Le Kang, Chinese Academy of Sciences, Beijing, China.
The molting process can take place several times in the life cycle of an insect, and each molting leads to a new instar or stage in its development. The adults emerge from the last instar (nymphs) through the final molting. Molting is therefore a crucial process in the growth and development of insects. Chitin, a polysaccharide, is a key component of the old and new cuticles of insects, but is absent from plants and vertebrates. Chitin plays key roles in the molting process, during which insect growth and development are strictly dependent on the precise control of chitin biosynthesis and degradation. As a consequence, the chitin metabolism pathway and the enzymes that catalyze it have become a research hotspot for developmental biology and a important source of targets for potential insecticides. In the August issue of PLOS Genetics, we found two new small RNAs associated with chitin biosynthesis and degradation, in which the balance of expression between these two RNAs regulated the locust molting process.
The migratory locust as an attractive model for molting
The migratory locust, a worldwide pest, goes through five molting stages in its life cycle. Disruption of genes encoding either chitin synthase or chitinase prevents larval molting, indicating a vital role for these functions during the molting process. Previously, we also confirmed that Dicer-1, an enzyme that is necessary for the biosynthesis of microRNAs (miRNAs), plays a crucial role in controlling the molting process of locusts. However, the connection between specific miRNAs and chitin metabolism has not yet been investigated.
Two miRNAs jointly regulate chitin metabolism to control locust molting
Our study elucidated a mechanism by which two miRNAs regulate aspects of chitin metabolism that are related to the molting process. We found that miR-71 and miR-263 directly repress the two genes chitin synthase1 (CHS1) and chitinase10 (CHT10), respectively. Manipulation of miR-71 and miR-263 expression blocked molting, and resulted in abnormal molting by negatively regulating the expression of CHS1 and CHT10. Interestingly, both up-regulation and down-regulation of CHS1 and CHT10 by miRNA manipulation altered the chitin content of the new cuticle and old cuticle, leading to a similar aberrant molting. This reveals a balancing effect between these two miRNAs in their effect on chitin biosynthesis and degradation.
Significance of findings
Firstly, our study highlights the potential for developing new methods of pest control. Secondly, our results provide an association between chitin metabolism and miRNAs. Finally, our findings show that miRNAs can be precisely fine-tuned to balance developmental transcription by increasing and reducing target expression to meet developmental demands.
Yang M, Wang Y, Jiang F, Song T, Wang H, Liu Q, et al. (2016) miR-71 and miR-263 Jointly Regulate Target Genes Chitin synthase and Chitinase to Control Locust Molting. PLoS Genet 12(8): e1006257. doi:10.1371/journal.pgen.1006257