Dissertation
Functions of effectors and small RNAs in wheat rust disease
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/111490
Abstract
Rust diseases caused by members of the genus Puccinia, are a major constraint to global wheat production. Efficient management of rust is a challenge due to the ability of the pathogen to rapidly alter its effector repertoire in response to recognition by resistance genes. Thus, judicial deployment of resistance genes necessitates a better understanding of fungal pathogenesis and host defense responses. Although large repositories of putative effectors have been predicted using bioinformatics pipelines, functional studies on effector proteins have been limited due to the lack of a suitable effector delivery system for wheat. In this study we identified two Pseudomonas species- P. fluorescens (EtHAn), and P. syringae D36E, as transient transformation systems for delivering effector proteins into wheat leaf cells. Additionally, a heterologous system was successfully used for screening twenty rust effectors from Puccinia graminis and P. stiriiformis, and nine effectors capable of attenuating host immune responses were identified using this system.
In addition to interactions at the protein level, host-pathogen interactions also occur at the level of RNA transcription. As part of the second aim of my project, we analyzed the small RNA profiles of two wheat cultivars, one susceptible (Penawawa) and one partially resistant (Louise) to P. striiformis, to better understand differences in gene regulation that occur during infection. A total of 163 novel miRNAs and 182 known miRNAs were identified using 12 small RNA libraries prepared from two wheat cultivars infected with P. striiformis. Of these miRNAs, 22 were differentially expressed (P-value < 0.05) between the two cultivars, while miR399 was differentially expressed during infection. These results were validated using RT-PCR and qRT-PCR. Targets of these miRNAs were identified with different target prediction software and validated using 5’ RACE. Overall, this work contributes to the current knowledge on the wheat-rust patho-system and will help improve existing management strategies for wheat rusts in the future.
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Details
- Title
- Functions of effectors and small RNAs in wheat rust disease
- Creators
- Sowmya Ramachandran
- Contributors
- Scot H Hulbert (Advisor)Xianming Chen (Committee Member)Michael Pumphrey (Committee Member)Kiwamu Tanaka (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Plant Pathology
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 167
- Identifiers
- 99900581629401842
- Language
- English
- Resource Type
- Dissertation