| Summary: | 博士 === 國立中興大學 === 生物科技學研究所 === 102 === In my Thesis, I studied the effects of ABA pathway on Plant-BaMV interactions. In the first chapter, I summarized the literature studies made on hormone-virus interactions, highlighting those important in plant defense/susceptibility to viruses and underlining the many points which require further researching. In the second chapter, I studied how ABA and mutants of ABA biosynthesis and signaling pathway differentially affect the accumulation of BaMV in two different hosts N. benthamiana and A. thaliana. The work showed that ABA2, the biosynthesis gene, has a distinct role by supporting the accumulation of BaMV, and that is opposite to the roles of other genes downstream ABA2. The results were supported by experiments on another virus: Cucumber Mosaic Virus (CMV), whose accumulation was also shown to necessitate a functional ABA2 gene. I also showed that N. benthamiana plants infected with BaMV or CMV exhibited upregulation in the transcript levels of several SA and ABA genes, and significant accumulation of ABA content. These findings concluded that ABA-SA antagonism was disrupted by the infection of either virus.
In the third chapter, I studied ABA-mediated defense against BaMV in Arabidopsis. I found that ABA positively affects the transcripts of several Argonauts. By using deficient lines of ABA biosynthesis, and overexpression line of ABA, supported with an experiment in which wild type plants were sprayed with ABA, I showed that ABA levels affect AGO1, 2, 3, 5, and 9. In the inoculated leaves, the ABA-mediated defense is probably due to the increase of some important Ago transcripts. Indeed, the overexpression of these AGOs in N. benthamiana reduced BaMV titer drastically, and highlighted the importance of AGO2, 3, 5, and 9 for plants in their resistance to BaMV. This work also showed that AGO1 and miR168a, the core elements in the RNAi system, are irrelative to the ABA-mediated defense.
In the forth chapter, I summarized my findings and discussed the perspective.
|
|---|
