Research

Hormonal regulation of insect molting and metamorphosis (Dr. Minakuchi's theme)

   Insect molting and metamorphosis are regulated by the molting hormone (ecdysone) and juvenile hormone (JH).  JH is an anti-metamorphic hormone that suppresses metamorphic changes.  Recently, several researchers succeeded in identifying some of the factors in JH signaling pathway: methoprene-toletant (Met) is likely the JH receptor, while Krüppel homolog 1 is a JH-response transcription factor downstream of Met.  Many of these studies were performed by RNAi experiments using the red flour beetle, Tribolium castaneum. 

   We are trying to elucidate the molecular mechanism of JH signaling in a variety of pest species.  These studies will help us to develop new insect growth regulators that are specifically effective against the target pest.

Insect immune system in Beetles (Dr. Minakuchi's theme)

   Insects produce antimicrobial peptides (AMPs) as part of their humoral immune system against foreign organisms. The mechanism by which AMP gene expression is regulated upon recognition of foreign substances has been studied in detail in model insects such as Drosophila melanogaster. As a result, the signal transduction pathway that leads to AMP gene expression via the Toll or Imd pathway, depending on the type of microorganism infected, has been clarified. Our research is aimed at elucidating the regulatory mechanism of AMP gene expression in Coccinellidae, a type of beetle. Recent experimental results have revealed the interesting finding that the regulatory mechanism of AMP gene expression differs from that in Drosophila melanogaster, and we are further analyzing this finding.

   In addition, the insect epidermis acts as a physical barrier against foreign invaders. We are trying to elucidate the role of the epidermis as a barrier by examining the effects of entomopathogenic fungi and insecticides on Coccinostomus infestans, whose epidermis formation has been suppressed by RNA interference methods.

Mechanism of insecticide resistance (Dr. Minakuchi's theme)

   In insects, some of the enzymes in cytochrome P450 family are the key players in insecticide detoxification.  But our knowledge on the molecular mechanism of insecticide metabolism is still limited. We are trying to disclose the mechanism of insecticide metabolism, especially in thrips.

Chemical communication mechanisms in termites (Dr. Mitaka's theme)

   Insects perceive chemicals, light, and sound (or vibration) to obtain information about their surroundings and to communicate with other individuals. Many insects use their olfaction and gustation to perceive chemicals in their environment for a variety of purposes including foraging, mating behavior, and searching for egg-laying substrates. In particular, social insects (ants, bees, termites, etc.) have developed a much more sophisticated chemical communication system than solitary insects. Within a colony of social insects, there are several groups of individuals that are behaviorally and morphologically specialized to perform a particular task, and these groups are called "castes". Each caste is engaged in caste-specific tasks, so the societies of social insects are based on division of labor. 

   Pheromones are chemical substances used for communication between organisms that innately elicit specific behavioral or physiological changes in other individuals of the same species. In our lab, we are exploring the evolutionary background that enabled termites to develop complex societies based on chemical communication by identifying the components and functions of termite pheromones and investigating the molecular mechanisms by which termites send and receive their pheromones. Also, we aim to use the findings to develop termite control methods that reverse the behavioral characteristics of termites.

　For more information on the research results, please visit the Mitaka's website.

Antimicrobial compounds produced by termties (Dr. Mitaka's theme)

   　Termites and other social insects are at risk of spreading certain diseases in their nests because they form colonies of many blood-related individuals. Therefore, they produce and use a wide variety of antimicrobial substances to disinfect and sterilize their nests and inhibit the invasion, germination, and growth of any pathogenic microorganisms.

　We are identifying the components and functions of the antimicrobial substances used by termites and unraveling the mysteries of their colony-level quarantine strategy. Understanding this strategy will help us to better understand the effectiveness of biological controls against termites and their resistance to insecticidal ingredients, which will in turn inform our control methods.

   For more information on the research results, please visit the Mitaka's website.