疫病菌OPEL同源性基因在植物反應所扮演的角色

The roles of OPEL homologs from Phytophthora parasitica in plant responses

卓濬哲(Chun-Che Cho)

指導教授 ： 劉瑞芬

國立臺灣大學/生物資源暨農學院/植物病理與微生物學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603205

摘要

在先前的研究發現OPEL為一新興elicitor，可在菸草 (N. tabacum) 引起細胞死亡、活性氧分子 (reactive oxygen species, ROS) 累積、堆積癒傷葡聚醣 (callose deposition)、誘導PAMP-triggered immunity (PTI) 相關基因表現和誘導產生系統性抗病 (systemic acquired resistance, SAR) 等防禦反應。本研究為了解OPEL是否為一種pathogen-associated molecular pattern (PAMP)，針對OPEL的同源性基因進行研究。首先以tblastn搜尋NCBI、JGI與Broad institute基因體資料庫中OPEL同源性基因繪製親緣演化樹，發現在卵菌中OPEL同源性基因有拷貝數 (copy number) 增加的現象，最大的基因拷貝數出現在植物病原卵菌中。比較各同源性基因間domain組成的異同，thaumatin-like domain只存在植物病原卵菌中，加上分析疫病菌glycoside hydrolase family 16 (GH16) 的親緣關係發現OPEL同源性基因自成一群，都顯示了OPEL同源性基因具有高度的獨特性。使用農桿菌注入法 (agroinfiltration) 分析OPEL同源性基因與植物的交互作用，PPTG_17496可在N. benthamiana造成壞疽 (necrosis)，而PPTG_16550、PPTG_17497與PPTG_17498可在N. tabacum引起局部細胞死亡，顯示疫病菌OPEL同源基因可被不同寄主辨識，並且引起的植物防禦反應不盡然相同，大大提升OPEL同源性基因作為PAMP的可能性。但是PPTG_17496在N. benthamiana上引起壞疽病徵需要10天，顯示植物PPTG_17496不是直接被植物辨識啟動防禦反應，可能是由酵素活性作用後產生的小分子 (DAMP) 引起植物的防禦反應，而OPEL同源性基因引起防禦反應是PTI還是DAMP-triggered immunity (DTI)，或著是兩者皆有，需要更進一步的研究。

關鍵字

OPEL ； glycoside hydrolase family 16 (GH16) ； Phytophthora parasitica ； PAMP-triggered immunity (PTI) ； DAMP-triggered immunity (DTI)

並列摘要

A previous study indicates OPEL is a novel elicitor, which induce cell death, reactive oxygen species (ROS) accumulation, callose deposition, PAMP-triggered immunity (PTI), and systemic acquired resistance (SAR) on Nicotiana tabacum. In this study, we focus on OPEL homologous genes to verify whether OPEL is a pathogen-associated molecular pattern (PAMP) or not. Phylogenetic analysis OPEL homologous genes by tblastn search on NCBI, JGI and Broad institute genome database has shown homologs of OPEL have gene duplication in oomycetes. Besides, oomycetes plant pathogens have the most copy number of OPEL homologous genes. Analysis domain conformation of OPEL homologs indicates thaumatin-like domain is a distinct domain in oomycetes plant pathogen. Phylogenetic analysis glycoside hydrolase family 16 (GH16) in Phytophthora parasitica demonstrated OPEL homologous genes are different from other GH16 genes. These study imply OPEL homologs are unique genes in oomycetes. To characterize the interaction between OPEL homologs and plants, we overexpress OPEL homologs of P. parasitica by using agroinfiltration. PPTG_17496 induces necrosis on N. benthamiana, and PPTG_16550, PPTG_17497, and PPTG_17498 induce small region cell death on N. tabacum. Both results indicate OPEL homologs are PAMPs. However, PPTG_17496 consume 10 days to establish necrosis symptoms on N. benthamiana, which may be caused by DAMP-triggered immunity (DTI) but PTI. We need further research to find out OPEL homologs induce PTI or DTI on plants.

並列關鍵字

OPEL ； glycoside hydrolase family 16 (GH16) ； Phytophthora parasitica ； PAMP-triggered immunity (PTI) ； DAMP-triggered immunity (DTI)

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