Role of Effector PopP3 in Virulence of Ralstonia solanacearum and Characterization of Phage Lysis Proteins
| Autor: | Hung-Wei Wu, 吳紅葳 |
|---|---|
| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 Ralstonia solanacearum (Rs), the causal agent of bacteria wilt (BW), has an unusual wide host range, including many important crops. R. solanacearum phylotype I strains confer varied degrees of virulence/aggressiveness on tomato plants; however, genetic information on pathogen virulence-related factors is still very limited. Our comparative genome sequence analysis identified a YopJ-type effector protein Pseudomonas outer protein P 3 (popP3) unique to a high-virulence strain Pss190. The first part of this thesis aimed to study function and property of PopP3 in Rs virulence. The results showed that overexpression of PopP3 in Rs medium-virulence strain Pss4 led to increased bacterial virulence in tomato. Transient local overexpression of PopP3 in Nicotiana benthamiana caused enhanced propagation of Rs. Transient overexpression of PopP3 in tomato suppresses pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI) related callose deposition and increases the susceptibility to the Pectobacterium carotovorum subsp. carotovorum (Pcc). popP3 transcription was positively regulated by the type III secretion system (T3SS) regulator HrpG. In addition, GFP-tagged PopP3 colocalized with the mitochondria of N. benthamiana protoplast. These results together suggest that PopP3 is a T3SS effector and contributes to the virulence of R. solanacearum by suppressing plant defense response which probably is related to mitochondrial functions. The second part of this thesis aimed to collect information on R. solanacearum phages and their lysis proteins. Genome annotation of a T7-like bacteriophage RsφP29 capable of lysing the medium-virulence Rs strain Pss4 revealed the existence of a group of novel proteins which may involve in host specificity. In addition, characterization of its lysis proteins showed that GST-L recombinant protein might not have in vitro anti-Rs activity and that the failure of expressing the H protein in E. coli might be due to its antibacterial activity. Interestingly, transient overexpression of RsφP29 H protein in tobacco caused cell death and this effect can be further promoted by the infection of different phytopathogenic bacteria or their T3SS-defective mutants. Furthermore, tomato plants systemically overexpressing H protein were more resistant to Rs and Pcc. These results enable us to propose an effect for RsφP29 H protein in eliciting damage-associated molecular patterns (DAMPs)-triggered immunity (DTI) in plant. In addition, nine groups of local phages with varied capability of lysing local and imported high-virulence Rs strains were isolated, and Rs strains with higher virulence generally were tolerant to these phages. The information collected from this thesis, regarding Rs virulence determinants, Rs-plant/phage interactions and related resources, would pave the way to further studies of these important aspects. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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