Characterization of pathogen-responsive genes involved in compatible interaction between orchid and Erwinia chrysanthemi

• Main Authors: Jing-Pei Liu, 劉璟霈
• Other Authors: Hao-Jen Huang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/61808000742516524549

碩士 === 國立成功大學 === 生命科學系碩博士班 === 97 === Plants respond to pathogen attack by activating arrays of inducible defense mechanisms. A previous study using suppression subtractive hybridization (SSH) strategy was applied in search for genes that were induced after infection of Phalaenopsis orchids by a bacterial pathogen, Erwinia chrysanthemi. As a result, a pool of 73 unique mRNA transcripts form Erwinia-infected orchids exhibited different expression profiles when compared to healthy plants. Among these, two candidate genes showed early responsiveness to Erwinia infection and were subsequently selected for functional analysis in this study. The first one is a enoyl-CoA reductase gene (PaECR), which encodes a enzyme that catalyzes the last step of very-long-chain fatty acids elongation. The other is a gene encoding a putative basic-leucine zipper transcription factor, termed PabZIP. Semiquantative RT-PCR analysis of gene expression showed that the steady-state level of the PaECR transcripts increased 6 hours (hrs) post-inoculation and remained elevated through 24 hrs. Furthermore, the gene expression of PabZIP was induced at 6 hrs after challenge with Erwinia. These genes were both strongly induced by Erwinia infection, confirming the SSH-based results. To understand the function of PaECR and PabZIP genes in orchid plants, loss-of-function study was performed by virus-induced gene silencing (VIGS) of the PaECR and PabZIP gene, respectively. Interestingly, the results indicated that silencing of PaECR in orchid plants enhanced the susceptibility to Erwinia. In summary, the study suggests that PaECR may play important roles in resistance to Erwinia. Further characterization and functional analysis of these genes will gain more insight into the molecular mechanisms underlying orchid-Erwinia interactions, which may lead to improvement of orchid agriculture.