Author ORCID Identifier

Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Agriculture, Food and Environment



First Advisor

Dr. Subba Reddy Palli


Insects undergo a series of distinct life stages such as egg, larva and pupa to develop into mature adults capable of reproduction throughout their life cycle. In the larval stage, insects experience the fastest growth with voracious feeding and multiple cuticle shedding resulting in hundreds-of-fold increasing of size. During metamorphosis, insects stop increasing body size but go through dramatic tissue transformation, developing wings and other adult features. The characteristic mode of insect development, especially the metamorphosis, makes insects the most successful group of animals on the earth. However, the epigenetic mechanisms behind insect development remain elusive. Studying the epigenetic regulation of insect development is important not only for advancing our understanding of the fundamental mechanism of insect development but also for helping identify new targets for the control of insect pests.

The first part of this dissertation identified the function of m6A mRNA modification in the development of the red flour beetle, Tribolium castaneum. RNAi-mediated knockdown of genes coding for m6A writers (proteins in m6A methyltransferase complex) and readers (recognizing and executing the function of m6A) was conducted. Knockdown of most writers during the larval stage caused the failure of ecdysis. Meanwhile, interfering m6A also sterilized females by interfering with the development of reproductive systems and embryogenesis. These data suggest that m6A modifications play a critical function in T. castaneum development.

In the second part, my research focused on an RNA-binding protein, LRPPRC (Leucine Rich Pentatricopeptide Repeat Containing). LRPPRC is a potential m6A reader. During the screening study in the above chapter, it was shown the knockdown LRPPRC blocks the ecdysis of T. castaneum metamorphosis, however surprisingly, it doesn’t affect the development of pupal and adult structures except for wings resulting in short and wingless phenotypes. Further study showed that LRPPRC regulates mitochondrial mRNA polyadenylation and stability, and the function of LRPPRC on insect metamorphosis is induced through mitochondria. Since LRPPRC/mitochondrion regulates insect wing growth, I hypothesized that it could serve as the target to control insects that are notorious in the adult stage such as the yellow fever mosquito, Aedes aegypti. CRISPR/Cas9-induced knockout of LRPPRC caused a decrease in larval body size, extended the developmental time of larvae, and increased mortality during the larval and pupal stages. Using nano-formulated LRPPRC dsRNA, a high mortality was observed, indicating the potential of mitochondrial genes for mosquito control.

The last part of my research focused on identifying the function of histone methylation in T. castaneum metamorphosis. By screening histone methyltransferase and demethylases, a few of them including KMT5A (Lysine Methyltransferase 5A) have been identified with important role in T. castaneum metamorphosis,. Further studies showed that KMT5A catalyzes H4K20 mono methylation and regulates metamorphosis by targeting 20-Hydroxyecdysone (20E) synthesis.

Digital Object Identifier (DOI)

Funding Information

This work was supported by grants from the National Institute Of General Medical Sciences of the National Institutes of Health under Award Number R01GM070559 and the National Institute of Food and Agriculture, US Department of Agriculture (under HATCH Project 2351177000) in 2017.

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Available for download on Wednesday, July 24, 2024