Defence transcriptome profiling of Zingiber zerumbet (L.) Smith by mRNA differential display

Soft rot is a serious disease in ginger (Zingiber of?cinale Roscoe),imposing a considerable economic loss annually in all ginger-producing countries. In this study,mRNA differential display was employed to identify genes whose expression was altered in a soft rot-resistant accession of Zingiber zerumbet (L.) Smith,a wild relative of ginger, in response to Pythium aphanidermatum (Edson) Fitzp.,which is the principal causative agent of soft-rot disease in ginger. Analysis using 68 primer combinations identified 70 differentially expressed transcript-derived fragments (TDFs),of which 34 TDFs were selected for further analysis following reverse northern screening. Cloning and sequence characterization of the 34 TDFs yielded a total of 54 distinct clones. Functional categorization of these clones revealed seven categories,of which the defence/stress/signalling group was the largest,with clones homologous to genes known to be actively involved in various pathogenesis-related functions in other plant species.The significance of these genes in relation to the resistance response in Z.zerumbet is discussed. This study has provided a pool of candidate genes for detailed molecular dissection of the defence mechanisms in Z.zerumbet and for accessing wild genetic resources for the transgenic improvement of ginger.