Erwinia chrysanthemi is a devastating bacterial pathogen in orchid horticulture and causes soft-rot diseases by secretion of cell wall-degrading enzymes. However, the pathogenesis and resistance response to the pathogen in the orchid remain to be elucidated. In this chapter, the molecular events of the early hostâ€“pathogen interaction between Phalaenopsis orchids and E. chrysanthemi are described on the basis of gene expression profiles. At the early stage of pathogenesis, the defense mechanism, such as an alteration in reactive oxygen species level, was elicited upon infection. For the analysis of the signal transduction pathway triggered by E. chrysanthemi infection, a PCR-based strategy using degenerate primers was performed to identify the genes encoding protein kinases and phosphatases. The genes coding for Phalaenopsis amabilis calcium-dependent proteinkinase 1 (PaCDPK1) and tyrosine phosphatase (PaPTP1) were isolated from the orchid, and their expression in response to pathogen infection and wounding were characterized. To gain more insight into the mechanisms underlying the compatible interactions, genome-wide transcriptional regulation was investigated by a suppression subtractive hybridization strategy. A total of 170 clones were sequenced from the whole cDNA library to generate 65 nonredundant pathogen-responsive transcripts. Among the genes with assigned function, 37 percent were associated with metabolism, 30 percent with environmental interactions, 13 percent with energy, and 20 percent with others. One of the pathogen-responsive transcripts encoding trans-2-enoyl-CoA reductase was the most abundant representative of plant genes, comprising 15 percent of the total clones. A putative model of the early molecular events in the orchid in response to E. chrysanthemi infection was proposed. The chapter provides valuable information towards the understanding the orchidâ€”E. chrysanthemi interaction at the molecular level.
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)
- Biochemistry, Genetics and Molecular Biology(all)