Gene Expression Associated with Soybean Defense to Redbanded Stink Bug - Piezodorus guildinii

Stink bugs are emerging as a major pest of soybean throughout the world. Their populations are increasing in countries such as the USA and Brazil and they are responsible for significant losses of yield and seed quality. To identify genes that might be associated with stink bug defense in soybean, we looked at gene expression levels from isolated pods that had been fed upon by redbanded stink bugs (Piezodorus guildinii) versus expression in control pods. The partially resistant (antibiosis) genotype IAC100 was compared to susceptible CD215 at 24 and 46 hours post-infestation (hpi), using plants grown in a field in Mississippi, USA. Four biological replicates were analyzed for each treatment, paired-end sequenced by an Illumina system (sequencing performed by the High-throughput Sequencing and Genotyping Unit, Roy J. Carver Biotechnology Center at the University of Illinois), processed by the Trinity freeware package, and the differential expression ratios and fdr corrected p-values calculated using the RNA-seq analysis software, RSEM. Preliminary analysis of the data from the 24 hpi samples generated 166,593 contigs from the 128,668,640 sequenced RNA fragments from IAC100. Alignment showed 59.8% hit a known soybean gene (Williams 82 GlymaID), another 37.6% hit elsewhere on the Williams 82 soybean reference genome, and only 2.6% did not align to the reference genome. Similar results were obtained for CD215. Comparisons of the frequencies of expression of each gene between the two cultivars, with or without insect feeding, and QTL resistance map locations, are being used to identify putative stink bug defense genes.