Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 2012
Publication Date: July 1, 2012
Citation: Tarver, M.R., Coy, M., Zhang, D., Scharf, M.E. 2012. Cyp15F1: A novel cytochrome P450 gene linked to juvenile hormone-dependent caste differention in the termite R. flavipes. Archives of Insect Biochemistry and Physiology. 80(2):92-108. Interpretive Summary: Termites are eusocial insects that jointly utilize juvenile hormone, pheromones and othersemiochemicals to regulate caste differentiation and achieve caste homeostasis. PriorEST sequencing from the symbiont-free gut transcriptome of Reticulitermes flavipes unexpectedly revealed a number of unique cytochrome P450 (Cyp) transcripts, including fragments of a Cyp15 family gene (Cyp15F1) with homology to other insect Cyp15s that participate in juvenile hormone (JH) biosynthesis. The present study investigated the role of Cyp15F1 in termite caste polyphenism and specifically tested the hypothesis that it plays a role in JH-dependent caste differentiation. After assembling the full-length Cyp15F1 cDNA sequence, we (1) determined its mRNA tissue expression profile, (2) investigated mRNA expression changes in response to JH and the caste-regulatory primerpheromones '-cadinene (CAD) and '-cadinenal (ALD), and (3) used RNA interference (RNAi) in combination with caste differentiation bioassays to investigate gene function at the phenotype level. Cyp15F1 has ubiquitous whole-body expression (including gut tissue); is rapidly and sustainably induced from 3-hr to 48-hr by JH, CAD and ALD; andfunctions at least in part by facilitating JH-dependent soldier caste differentiation. These findings provide the second example of a termite caste-regulatory gene identified through the use of RNAi, and significantly build upon our understanding of termite caste homeostatic mechanisms. These results also reinforce the concept of environmental caste determination in termites by revealing how primer pheromones, as socio-environmental actors, can directly influence Cyp15 expression and caste differentiation.
Technical Abstract: Termites are eusocial insects that perform social interactions that facilitate chemical signaling. Previous research identified two cytochrome P450s that have homology to other insect p450s responsible for the production of juvenile hormone. Juvenile hormone is an important morphogenic hormone that plays a direct role in termite caste differentiation. The object of this research was to obtain the full length gene sequence, tissue expression change to JH and regulatory primer pheromones '-cadinene (CAD) and '-cadinenal (ALD), and (3) used RNA interference to investigate the cyp15’s gene function at the molecular and organismal levels. Our findings reveal that cyp15’s are expressed in the head and gut and respond to JH and primer pheromones and possibly play a direct role in caste differentiation. These findings also significantly enhance our understanding of termite caste differentiation and suggest similarities between termites and other insects in JH physiology. These results also will greatly enhance our knowledge on termite physiology and will help lead to the identification of new target sites for control.