GENES CONTROLLING SOCIAL BEHAVIOR IN ANTS

点击翻译按钮获取中文摘要

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Specific aim #1: Identify fire ant homologs of bee genes predictive of task behavior. Our previously isolated PCR product, 1PXIR, which is similar to the honey bee or Drosophila foraging gene (protein kinase G, PKG) was used to design a PCR primer to identify a longer sequence of the fire ant homolog of PKG. 1PXIR corresponds to a position that is about 500 nucleotides from the stop codon of honey bee PKG mRNA. Using a 23 nucleotide 5' primer and a 27 nucleotide 3' primer based on the Apis PKG sequence, we obtained a range of 300-400 bp PCR products. These were inserted into a pGem sequence vector. No DNA sequences corresponding to PKG were obtained. We have designed new PCR primers for PKG based the Apis and Drosophila foraging gene rather than 1PXIR, and the isolation of the sequence is in progress. Specific aim #2: Correlate known social task-specific size changes in brain regions with differences in gene expression.We extracted mRNA from workers to develop a cDNA library in pBluescript for subsequent differential display experiments. Colonies containing inserts were obtained, but those inserts which we spot-checked by sequencing were too small to be useful. A rabbit antibody to fire ant apolipophorin III was generated and purified by affinity chromatography. Frozen sections of male and worker heads were examined by immunocytochemistry, using rabbit anti-apolipophorin III as the first antibody and AlexaFluor 594 donkey anti-rabbit IgG as the second antibody (red emission is necessary to avoid cuticle yellow autofluorescence). Expression was found in epithelial layers underlying the cuticle in both males and workers, and also throughout the brain. The coding sequence for the polygyne queen-specific hydrophobic ligand-binding protein Gp-9b was inserted into a pET22 expression vector and expressed in E. coli. The expressed protein will be used to generate a rabbit antibody. Specific aim #3: Silence expression of specific genes to test for loss of social behavior. A behavior assay was developed for subsequent use in evalulating effects of RNAi experiments. We measured the autocorrelation function, c(t) = (1/T) ? [A(t) A(t + t)], of ant number fluctuations, where A is the number of ants in a defined area of an artificial nest, T is the total time, t is a particular time point, and t is a variable time offset. We found that c(t) decays as an exponential function, with a correlation time tc. Through modeling of random motion, we showed that tc is directly proportional to the average velocity of the ants in a group. Thus, by measuring the number autocorrelation function, we can obtain information about the collective motion of a group of ants.