Thesis Title

Molecular Studies Of Virus-Induced Gene Silencing In Nicotiana Benthamiana And Six Defense-Related Genes In Grapes


Xueyan Zhong

Date of Graduation

Spring 2004


Master of Science in Plant Science



Committee Chair

Wenping Qiu


My thesis projects are related to two plant defense mechanisms: RNA silencing and pathogen-induced disease resistance. In the first project, the fate of non-viral fragment in recombinant plant virus was investigated in a model system consisting of Tomato bushy stunt virus (TBSV) and its defective interfering RNA (DI), and host plants, Nicotiana benthamiana and its relative that was transformed with a green fluorescent protein (GFP) gene. RNA gel blots demonstrated that non-viral GFP fragments remained in TBSV and DI population only on GFP transgenic N. benthamiana plants in which virus-induced gene silencing (VIGS) was initiated, but were removed from TBSV and DI population on wild type N. benthamiana plants. TBSV P19, the suppressor of VIGS, has little effect on the outcome of non-viral fragment in DI population. These results imply that the homologous recombination of TBSV and DI to remove non-viral sequence is influenced by the gene silencing pathway. In the second project, six defense-related genes from a disease-resistant Norton grapevine (Vitis aestivalis 'Norton') were comparitively studied with their orthologs from disease-suspectible V. vinifera and other plant species. Sequence analyses indicated that each V. aestivalis 'Norton' gene differed, to a varying degree, from its respective V. vinifera counterpart. Expression profiles of the six genes in V. aestivalis 'Norton' and V. vinifera 'Cabernet Sauvignon' were also analyzed using RNA gel blots; however, the assays did not produce consistent results. These sequence and RNA gel blot analyses provided preliminary clues on genetic determinants that render V. aestivalis 'Norton" more resistant to diseases than V. vinifera.


plant defense, virus-induced gene silencing, Tomato bushy stunt virus, defective interfering RNA, grape, defense-related gene

Subject Categories

Plant Sciences


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