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Title: Socio-environmental influences on 1 developmental and caste-regulatory gene expression in the eusocial insect Reticulitermes flavipes

Author
item Tarver, Matthew
item ZHOU, XUGUO - University Of Florida
item SCHARF, MICHAEL - University Of Florida

Submitted to: BioMed Central (BMC) Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2010
Publication Date: 4/23/2010
Citation: Tarver, M.R., Zhou, X., Scharf, M. 2010. Socio-environmental influences on 1 developmental and caste-regulatory gene expression in the eusocial insect Reticulitermes flavipes. BioMed Central (BMC) Molecular Biology. (11)28:1471-2199.

Interpretive Summary: Termite caste differentiation is controlled by multiple caste intrinsic and extrinsic factors. This research was conducted in order to better understand the specific mechanisms that regulate and control termite caste differentiation. This research simultaneously monitored phenotypic caste differentiation and gene expression in the termite, Reticulitermes flavipes. Through use of quantitative real-time PCR, the expression patterns of 47 genes in response to JH and soldier head chemicals were investigated. The three main groups of genes with significant differential expression were 1) genes encoding enzymes involved in hormone and semiochemical biosynthesis / degradation, 2) hemolymph protein coding genes, and 3) developmental genes. This research provides new insights into the impacts that socio-environmental factors (JH, soldiers, primer pheromones) can have on termite gene expression and caste differentiation, and reveals a number of socially-relevant genes that should be investigated in subsequent research concerning caste differentiation.

Technical Abstract: Strict regulation of caste differentiation, at the molecular level, is thought to be important to maintain social structure in insect societies. Previously, a number of extrinsic and intrinsic factors have been shown to influence caste composition in termite colonies. One important factor is the influence of nestmates; in particular, soldier termites can inhibit hormone-dependent worker-to-soldier differentiation. However, soldier influences on nestmates at the molecular level are virtually unknown. Here, to test the hypothesis that soldiers can influence nestmate gene expression, we investigated the impact of four treatments on gene expression in totipotent Reticulitermes flavipes workers: (i) juvenile hormone III (JHIII; a morphogenetic hormone), (ii) soldier head extracts (SHE), (iii) JHIII+SHE, and (iv) live soldiers. Using quantitative-real-time PCR we determined the expression patterns of 49 previously identified candidate genes in response to the four treatments at times ( days 1, 5, and 10). Thirty-eight total genes from three categories (chemical production/degradation, hemolymph protein coding and developmental)showed significant differential expression among treatments. Most importantly, SHE and live soldier treatments had a significant impact on a number of genes from families known to play significant roles in insect development, supporting previous findings and hypotheses that soldiers regulate nestmate caste differentiation via terpene primer pheromones contained in their heads. This research provides new insights into the impacts that socio-environmental factors (JH, soldiers, primer pheromones) can have on termite gene expression and caste differentiation, and reveals a number of socially-relevant genes that should be investigated in subsequent research concerning caste differentiation.