Immune And Neural Response Of Locust To Fungal Infection And Transcriptional Characteristics Of Chemosensory Genes In The Fire Ant

Immune system and central nervous system(CNS) are essential for the survial of animals in responses to stress conditions, including both biotic and abiotic stress. Unlike higher animals, insects lack adaptive immunity. Their immune resonses to pathogen infection mainly rely on innate immunity. Hemocyte and fat body are the primary immune tissues. Although significant information concerning the immune functions of hemocytes and fat bodies in some holometabolous model insects has been obtained, far less is known concerning these two tissues in hemimetabolous orthopterans. CNS plays essential roles in insects defending against pathogen infection and may work as a controller to regulate proper immune response to defend against pathogen infection. However, the transcriptional response of insect CNS to pathogen infection know little. Chemosensory and olfaction are important components to detect and respond to pathogens. Among them, two protein families, namly, chemosensory and odorant binding proteins(CSPs and OBPs), play crucial roles in chemical sensation. The understanding of the expression profiles of these genes promotes to reveal their functions in pathogen detection, espectially the molecular mechanisms of social insects to sense and avoid infected individuals. Thus, we sought to provide a systematic analysis of the global gene expression responses of discrete immune and CNS tissues to a specific fungal pathogen of locusts and analyze the tissue expression profile of CSPs and OBPs in the red imported fire ant, Solenopsis invicta.Comparative transcriptomic analysis of the hemocyte and fat body of locust in response to infection by entomopathogenic fungi Comparative transcriptomic analyses were performed to investigate the global gene expression responses of hemocytes and the fat body of Locusta migratoria manilensis during infection by the locust-specific fungal pathogen, Metarhizium acridum. These data revealed that the fat body responds to fungal infection mainly through activation of genes involved in innate immune, energy metabolism and development. In contrast, hemocytes gene expression responses mainly affected gene involved in membrane regulation, activation of cellular immune responses, and release of humoral immune factors. Specifically, after fungal infection, within the identified immune related genes in the locust gene expression responses, 58 and 3 unigenes were found to be significantly differentially expressed in the fat body and in hemocytes respectively. 43 unigenes were commonly differentially expressed in both tissues, including lysozyme(Lm Lys4).CSN response of locust to fungal infection Temporal CSN responses of locust to six representative infection stages of M. acridum were dissected. Effects were seen at the earliest time points(4 h post-infection) and the number of differentially expressed genes(DEGs) was highest during hemocoel proliferation(72 h post-infection). Significantly affected neurological pathways included genes involved in serotonergic, cholinergic, dopaminergic, GABAergic, and glutamergic synapse responses, as well as pathways responsible for synaptic vesicle cycle, long-term potentiation and depression, and neurotrophin and retrograde endocannabinoid signaling. In addition, a significant number of immune related DEGs were identified in the CNS global gene expression response to fungal infection. These included components of the Toll, Imd and JAK/STAT pathways, indicating that the CNS itself is capable of mounting immunerelated responses. The overall gene expression patterns observed are consistent with the hypothesis of CNS monitoring of infection can result in behavioral and other responses that can seek to integrate with the immune system to counteract the pathogen attack.Expression chemosensory and odorant binding proteins(CSPs and OBPs) in a social insect Insect, especially social ones that engage in behaviors such as grooming, nestmate care, and removal of their dead, have evolved mechanisms for detecting microbial pathogens. CSPs and OBPs are small molecular weight proteins implicated in odorant binding, communication, and as general ligand binding proteins involved in many physiological processes including transport in the hemolymph. In order to provide a baseline dataset for future comparative analyses, we have examined the tissue expression profiles of the set of CSPs(21 total) and OBPs(17) in the different castes, tissues, and developmental stages of the red imported fire ant, Solenopsis invicta. Our results revealed that SiOBPs and SiCSPs show distinct caste and tissue expression preferences with sub-groups of evolutionarily related proteins showing similar expression patterns.These data form the critical information provided for further exploration of these proteins in relation to individual insect immunity, neuron defense, and exploitation of chemosensory defense mechanism of social insects defending against the microbial pathogens.