ARS | Publication request: Applying RNA Sequencing to investigate pathogenic mechanisms of Ascochyta rabiei

Submitted to: International Ascochyta Workshop
Publication Type: Abstract Only
Publication Acceptance Date: March 4, 2012
Publication Date: April 20, 2012
Citation: Qiu, D., Vandemark, G.J., Chen, W. 2012. Applying RNA Sequencing to investigate pathogenic mechanisms of Ascochyta rabiei. International Ascochyta Workshop. Page 27.

Technical Abstract: Ascochyta rabiei causes Ascochyta blight of chickpea. To study the pathogenic mechanisms of A. rabiei, total mRNAs were isolated from isolates AR19 of pathotype I and AR628 of pathotype II of A. rabiei, and also from diseased tissues of chickpea ‘Spanish White’ inoculated with these two isolates at times from 6 to 96 hours post inoculation (hpi), and were sequenced with the 454 Titanium RNA sequencing technology. The transcripts in the interacting transcriptomes were separated into either plant RNA or pathogen RNA based on BLAST searches, and the pathogen transcripts were compared with the transcripts of the pathogen from pure culture. The pathogen transcripts that were not found in the transcripts of pure culture were considered as induced transcripts (in response to infecting chickpea). A total of 21,226 and 28,061 unique transcripts (unigenes) were obtained from AR19 and AR628, respectively, and about 70% of them matched annotated genes in NCBI database. An average of 29,725 unigenes for each library was assembled from a total of 867,855 raw reads in the interacting transcriptomes. About 10% of unigenes were from the pathogen. There were 132 induced unigenes of isolate AR19 in the first 12 hpi, nine of them were highly expressed during 24 to 96 hpi, and 42 of them were consistently expressed up to 96 hpi. There were 178 induced unigenes of isolate AR628, six of them were highly expressed during 24 to 96 hpi, and 69 of them were consistently expressed up to 96 hpi. Analysis showed a strong induction for the expression of pathogen genes that belonged to different functional categories. The functions of these induced genes and their roles in pathogenesis remain to be investigated.