Abstract:

In an attempt to elucidate the molecular mechanism for resistance of black spot disease in poplar, gene expression profiles in leaves of Populus deltoides 'Lus’ (I-69/55) and P. euramericana 'I-45/51’,which were inoculated with the pathogen Marssonina brunnea f. sp. brunnea, were analyzed based on expressed sequence tags (ESTs). A total of 20 023 valid ESTs from the 5’terminal ends derived from corresponding cDNA libraries of the two poplar species were sequenced. Cluster analysis of the 20 023 sequences yielded 10 816 tentative unigenes, including 3 734 contigs and 7 082 singletons. All tentative unigenes were classified by Gene Ontology functional categories. To find resistance-associated candidate genes and locate them on poplar genome, 330 unigenes was chosen from 8 853 annotated tentative unigenes, and their BLAST alignment was conducted with Populus trichocarpa assembly, 177 related candidate resistant genes were found, and they presented in 282 unigenes. Among these genes, there were 135 genes located on 18 different linkage groups of poplar genome, and 42 genes located on the different scaffolds. This study supplied a resource of candidate genes for further exploring the genetic mechanism for the host horizontal resistance to the pathogen Marssonina brunnea at the whole genome range, and provided important information for further gene discovery.

Key words: poplar, expressed sequence tags, resistance-associated candidate gene, expression profile