Project description:RNA was extracted from a pooled sample of salivary glands that were excised from adult Diuraphis noxia aphids of two biotypes SA1 and SAM2.0. South African D. noxia biotype SA1 is known to be the least virulent aphid, while its offspring, the South African D. noxia biotype SAM2.0 is a newly developed biotype that is capable of feeding on several resistant cultivars. The overall purpose of the experiment was to establish a baseline availability of transcripts contained in the salivary glands of D. noxia aphids as well as help improve on current genome assemblies. In total, 200 glands were excised from both biotypes feeding on various wheat hosts (Tugela, Tugela Dn1, Gamtoss R, SST387). Aphid glands were excised in PBS buffer and stored in RNA-later until RNA extraction with a Qiagen Rneasy kit could commence. Library preparation for sequencing was performed using an Illumina TruSeq Stranded mRNA LT Sample Prep Kit following the TruSeq Stranded mRNA Sample Preparation Guide, Part # 15031047 Rev. E protocol. The single library was then sequenced on a NovaSeq6000 system. De novoassembly was performed making use of the Trinity package.
Project description:The molecular bases of aphid virulence to aphid crop plant resistance genes are poorly understood. The Russian wheat aphid, Diuraphis noxia, (Kurdjumov), and the greenbug, Schizaphis graminum (Rondani), are global pest of cereal crops. Each species damages barley, oat, rye and wheat, but S. graminum includes fescue, maize, rice and sorghum in its host range. This study was conducted to compare and contrast the transcriptomes of S. graminum biotype I and D. noxia biotype 1 when each ingested phloem from leaves of varieties of bread wheat, Triticum aestivum L., containing no aphid resistance (Dn0), resistance to D. noxia biotype 1 (Dn4), or resistance to both D. noxia biotype 1 and S. graminum biotype I (Dn7, wheat genotype 94M370). Gene ontology enrichments, k-means analysis and KEGG pathway analysis indicated that 94M370 plants containing the Dn7 D. noxia resistance gene from rye had stronger effects on the global transcriptional profiles of S. graminum and D. noxia relative to those fed Dn4 plants. S. graminum responds to ingestion of phloem sap from 94M370 plants by expression of unigenes coding for proteins involved in DNA and RNA repair, and delayed tissue and structural development. In contrast, D. noxia displays a completely different transcriptome after ingesting phloem sap from Dn4 or 94M370 plants, consisting of unigenes involved primarily in detoxification, nutrient acquisition and structural development. These variations in transcriptional responses of D. noxia and S. graminum suggest that the underlying evolutionary mechanism(s) of virulence in these aphids are likely species specific, even in cases of cross resistance.