Tissue-Specific Transcriptomics of the Exotic Invasive Insect Pest Emerald Ash Borer (Agrilus planipennis)

BACKGROUND: The insect midgut and fat body represent major tissue interfaces that deal with several important physiological functions including digestion, detoxification and immune response. The emerald ash borer (Agrilus planipennis), is an exotic invasive insect pest that has killed millions of ash trees (Fraxinus spp.) primarily in the Midwestern United States and Ontario, Canada. However, despite its high impact status little knowledge exists for A. planipennis at the molecular level. METHODOLOGY AND PRINCIPAL FINDINGS: Newer-generation Roche-454 pyrosequencing was used to obtain 126,185 reads for the midgut and 240,848 reads for the fat body, which were assembled into 25,173 and 37,661 high quality expressed sequence tags (ESTs) for the midgut and the fat body of A. planipennis larvae, respectively. Among these ESTs, 36% of the midgut and 38% of the fat body sequences showed similarity to proteins in the GenBank nr database. A high number of the midgut sequences contained chitin-binding peritrophin (248)and trypsin (98) domains; while the fat body sequences showed high occurrence of cytochrome P450s (85) and protein kinase (123) domains. Further, the midgut transcriptome of A. planipennis revealed putative microbial transcripts encoding for cell-wall degrading enzymes such as polygalacturonases and endoglucanases. A significant number of SNPs (137 in midgut and 347 in fat body) and microsatellite loci (317 in midgut and 571 in fat body) were predicted in the A. planipennis transcripts. An initial assessment of cytochrome P450s belonging to various CYP clades revealed distinct expression patterns at the tissue level. CONCLUSIONS AND SIGNIFICANCE: To our knowledge this study is one of the first to illuminate tissue-specific gene expression in an invasive insect of high ecological and economic consequence. These findings will lay the foundation for future gene expression and functional studies in A. planipennis

An insertional mutagenesis programme with an enhancer trap for the identification and tagging of genes involved in abiotic stress tolerance in the tomato wild-related species Solanum pennellii

Salinity and drought have a huge impact on agriculture since there are few areas free of these abiotic stresses and the problem continues to increase. In tomato, the most important horticultural crop worldwide, there are accessions of wild-related species with a high degree of tolerance to salinity and drought. Thus, the finding of insertional mutants with other tolerance levels could lead to the identification and tagging of key genes responsible for abiotic stress tolerance. To this end, we are performing an insertional mutagenesis programme with an enhancer trap in the tomato wild-related species Solanum pennellii. First, we developed an efficient transformation method which has allowed us to generate more than 2,000 T-DNA lines. Next, the collection of S. pennelli T0 lines has been screened in saline or drought conditions and several presumptive mutants have been selected for their salt and drought sensitivity. Moreover, T-DNA lines with expression of the reporter uidA gene in specific organs, such as vascular bundles, trichomes and stomata, which may play key roles in processes related to abiotic stress tolerance, have been identified. Finally, the growth of T-DNA lines in control conditions allowed us the identification of different development mutants. Taking into account that progenies from the lines are being obtained and that the collection of T-DNA lines is going to enlarge progressively due to the high transformation efficiency achieved, there are great possibilities for identifying key genes involved in different tolerance mechanisms to salinity and drought