Study of the molecular mechanisms and morphological analysis of structures involved in chemoreception in Capnodis tenebrionis (Coleoptera, Buprestidae)

Insects use chemical perception to interact with biotic and abiotic environmental factors. The perception of volatiles is mediated by molecules belonging to gene families, namely Olfactory Receptors (ORs), Ionotropic Receptors (IRs), Chemosensory Proteins (CSPs) and Odorant Binding Proteins (OBPs). Capnodis tenebrionis (Coleoptera, Buprestidae) infests mainly apricot, cherry, peach and plum. It colonizes the wide geographical area of the Mediterranean. The adult consumes bark and buds while larvae dig subcortical galleries in root cambium and phloem, compromising the vegetative and productive activity of the plant. The control of this pest lacks of monitoring strategies, such as information on insect chemical ecology. The composition of perceived volatile organic compounds (VOCs), as well as their emission rates, play an important role in determining the signal specificity for C. tenebrionis repulsion or attraction. The VOCs emission from control plants and from drought elicited plants was investigated through off-line (GC-MS) and online (PTR-MS) spectrometric techniques. The identification of the gene expression profile was carried out through an "omics" approach, based on RNA-seq, de novo construction and annotation of male and female adults transcriptome, using Blast2GO and searching for transcripts coding for proteins involved in the olfactory perception processes. Subsequently, OBPs and other transcripts putatively involved in olfactory perception were identified using BLAST searches and protein domain signatures. To investigate the putative roles of chemosensilla involved in the selection of the host plant, scanning electron microscopy (SEM) was performed on male and female C. tenebrionis individual antennomers. Chaetica, basiconica and coeloconica sensilla were recognized on the antennae. Coeloconica multipore sensilla were often found in pits on the paraxial and antiaxial faces of V-XI flagellomers.