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Dissertation_Junyan Lin v8.0.pdf (2.24 MB)

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NONHOST RESISTANCE TO BEAN POD MOTTLE VIRUS IN NICOTIANA BENTHAMIANA

Lin, Junyan
http://rave.ohiolink.edu/etdc/view?acc_num=osu1372723537

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Food, Agricultural and Biological Engineering.
Nonhost resistance refers to the microbial resistance mounted at the species level, namely none of the cultivars of the (plant) species is susceptible to a given pathogen. This form of disease resistance is considered to be the most robust and durable form of plant resistance. However, little is known about how nonhost plants engage viral pathogens. The goal of my thesis research was to elucidate the mechanisms of anti-viral nonhost resistance using Bean pod mottle virus (BPMV) and Nicotiana benthamiana (Nb) as experimental models. BPMV is a single-stranded, positive sense (+) RNA virus with two separately encapsidated genomic RNAs - RNA1 and RNA2. Nb – a common model plant – is a nonhost to BPMV. Soybean and lima bean, two host plants of BPMV, were also examined in parallel with Nb to uncover the differences in responses to BPMV infection that might contribute to nonhost resistance. I first examined the replication efficiency of BPMV RNAs in Nb cells. A GFP-tagged BPMV was introduced into Nb and its RNA accumulation level as well as its protein expression was evaluated. In the presence of P19, a heterologous virus suppressor of RNA silencing, BPMV RNA1 replication was readily detectable in the Nb nonhost cells, whereas RNA2 replication was detected only after a significant delay. These results suggested that Nb resists BPMV invasion by selectively targeting the replication of BPMV RNA2. Furthermore, RNA silencing is an integral component of the anti-BPMV nonhost resistance, as neither BPMV RNA1 nor RNA2 was detectable in Nb cells in the absence of P19. Since RNA2 was selectively repressed by Nb, The next objective was to identify unique features encoded by BPMV RNA2 that could be targeted by the nonhost resistance using the lima bean and soybean host systems. BPMV RNA2 encodes two unique cis-acting elements: the first is a cis-acting RNA element located at 5’ untranslated region (UTR) that was determined to be critical for the synthesis of negative (-) sense of RNA2. This element, referred to as stem-loop C (SLC), consists of a big, 15 base end loop, and a stem of 16 base pairs interspersed with one single-base bulge and one two-base mismatch. The other cis-acting element is a 58 kilodalton (K) protein (P58) encoded by RNA2. Mutagenesis of P58 indicated that the N-terminal 14k domain of P58 is sufficient to support the accumulation of RNA2. N-terminal extension of P58 compromised BPMV infectivity. Furthermore, a series of complementation experiments were designed and confirmed that the P58 is a cis-acting protein that assisted only the RNA from which it is translated. Overall, the completion of my thesis project reveals for the first time that nonhost plants attacked by bipartite RNA viruses could mount effective defenses by selectively targeting one of the genome segments. I also uncovered critical differences in the replication of the genome segments of the bipartite BPMV. These discoveries will contribute to the exploitation of nonhost resistance resource to achieve effective control of BPMV infection in soybean plants.
Qu Feng (Advisor)
147 p.
Plant Pathology

Recommended Citations

Citations

  • Lin, J. (2013). NONHOST RESISTANCE TO BEAN POD MOTTLE VIRUS IN NICOTIANA BENTHAMIANA [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372723537

    APA Style (7th edition)

  • Lin, Junyan. NONHOST RESISTANCE TO BEAN POD MOTTLE VIRUS IN NICOTIANA BENTHAMIANA. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1372723537.

    MLA Style (8th edition)

  • Lin, Junyan. "NONHOST RESISTANCE TO BEAN POD MOTTLE VIRUS IN NICOTIANA BENTHAMIANA." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372723537

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.